Tag Archives: climate-change

LECTURE: Are We F**ked by Climate Change?

John Langton, Ph.D.
Westminster College

“If we destroy creation, creation will destroy us.”
Pope Francis

In August I will be starting my thirty-sixth year of teaching political science at Westminster College, and I have been wondering since 1989, after hearing a “last lecture” by a young, popular economics professor, who was departing to teach at another school, what I would say, what crucial wisdom I would try to impart to my students, my colleagues, and perhaps the world at large if I were asked to give an honorary last lecture, based on the conceit or useful fiction that it would be my final talk ever, my last chance to make a difference before retiring from the scene “permanently.” On June 1 this abstract, philosophical question became an immediate, practical task when the Dean invited me to deliver a last lecture on July 31, 2016, the final morning of Westminster’s inaugural Summer Retreat for alumni, faculty and students.1

I thought a lot about what I might say. I like to think I have insights to share on a number of subjects, but I concluded that I would speak about climate change and politics, after my family took a vacation in mid-July to visit my brothers in California, which was and is still suffering through the fifth year of the severest drought to have struck the state in 1,200 years.2 Wildfires were burning out of control in various locations and motels from Laguna Beach to San Francisco displayed warning signs, announcing the drought and asking their patrons to conserve water. At the John Muir Woods, I asked a park ranger if the giant Redwoods in the area were threatened and she said they were suffering because climate change had reduced the fog from which they normally derive half the 55 gallons of water they need each day (the other half comes from groundwater).

I have been teaching Environmental Policy and Politics for more than 20 years and I have become convinced that environmental degradation in general and climate change in particular pose the preeminent, existential threat to the survival and well-being of the human species and countless other species as well.3 Climate change not only creates serious ecological, economic and health problems by itself but also exacerbates a whole array of other vexing conditions from poverty and acute inequality to illegal immigration, civil and ethnic strife, interstate conflicts and ultimately, I believe, the threat of nuclear war.4 Without getting control of climate change, it is going to become increasingly difficult for us and particularly for future generations to lead decent, healthy, civilized lives. To put it more bluntly, I am convinced that unless we drastically reduce the amount of CO2 (and other greenhouse gases) that we are now putting into the atmosphere, we are going to be royally, hellishly f**ked by climate change and its cascading, catastrophic consequences. That’s the thrust of my last lecture.

Originally, I had a more sedate, more traditional academic title for my last lecture and I wrote out a dense outline of what I wanted to say so that my final talk would have more structure than my usual classroom lectures. But, at a local bar on Thursday night, before the formal beginning of the retreat on Friday, one of my former students thanked me for really challenging her, and she and a number of other alumni said they had come to the retreat specifically to hear me hold forth, to “pontificate,” to give a typical free-flowing, off-the-cuff, irreverent Langton lecture. And so that’s what you’re getting this morning, with the proviso that I will try to follow the major points in my outline, which you now have before you.

I decided to change the title of my lecture to make it more provocative, more memorable and thus to give my “final talk” a better chance to be published and disseminated to a wider audience. I don’t mean to offend people by using the term f**ked. Rather I want to convey as graphically and effectively as possible that unless we stabilize climate change, we are going to be ruined, screwed, degraded, totally messed up, FUBARed, as American GIs in WWII used to say.5

To give credit where credit is due, I derived the title of my lecture from the title of Brad Werner’s highly technical paper, “Is Earth F**ked?” which he delivered in 2012 at the annual conference of the American Geophysical Union in San Francisco (where else?). Werner’s answer to his question was, “more or less,” “…as evidenced by widespread inability to meaningfully address such global challenges as climate change and soil degradation…within the dominant culture…”6 My answer to the question posed in the title of my last lecture, the wisdom I so desperately want to impart here is that “we are probably f**ked by climate change but not necessarily, not ineluctably.” We can save our planet and ourselves but it is going to take an incredible amount of sustained, intelligent work, large sacrifices, wise and courageous political leadership, systemic reforms, and, crucially, a massive, global “metanoia” or fundamental change of consciousness about the magnitude of the threat we face from climate change and what must be done to avoid being royally, hellishly f**ked by it. I hope you will pardon my repetition of that phrase for rhetorical effect, but, damn it, if we don’t act decisively to mitigate the emission of greenhouse gases and thus anthropogenic climate change, we will be FUBARed. And that’s the unvarnished truth, as I see it.

My Thesis and Basic Argument

Plato defined political wisdom in his Republic as knowing what is “the best possible conduct for the state as a whole…”7 and the knowledge I would like to convey here is that although we are in all probability going to be f**ked by climate change, this does not have to be our fate, if we can change our conduct, if we can just shed our addiction to fossil fuels before it is too late. We still have the time, knowledge and technological resources to stabilize climate change at a point that avoids the worst scenarios now envisioned by the IPCC. But we must recognize and treat climate change as the greatest existential threat, not just to American national security, but to the security of the human species, and we must act on that realization immediately, decisively, and dramatically to ensure that the average global temperature of the planet does not go higher (for a number of years) than 2 °C or 3.6 °F above the preindustrial baseline (1880–1910) average of about 13.7 °C or 56.7 °F.8 Concretely, to achieve this imperative, to have a sustainable future, four incredibly difficult steps must be taken: (1) we (the human species) must reduce the current roughly 40 billion metric tons of CO2 and the billions of tons of other greenhouse gases like methane, nitrous oxide, and hydrofluorocarbons we are currently emitting each year by burning coal, oil and natural gas9 by 80 percent by 2050 and then to zero by 208510; (2) we must leave approximately 85 percent of the known fossil fuel reserves underground11; (3) the United States, as one of the greatest emitters historically of the greenhouse gases currently in the atmosphere and as the most powerful and wealthiest nation on the planet, must lead this daunting project,12 but (4) we (Americans) can’t do this without first “fixing our politics,” as President Obama put it in his last State of the Union Address.13 Taking these steps would be, I firmly believe, the truly wise course of action for the United States and the world community in the most expansive, necessary and crucial sense of the phrase.

A good argument, a good plan of action, a good political theory, I tell my classes, offers sound reasons for a conclusion and typically tries to answer three questions: (1) what is and will be the case empirically, if current trends continue; (2) what ought to be the case, morally and practically (this is often referred to as the “vision” question); and (3) what should be done to go from here to there, to move from where we are to where we ought to be (this is the question about a feasible, effective transformation strategy). In the remainder of this lecture, I would like to sketch my answers to these questions with respect to the greatest challenge we face as a species: unmitigated climate change driven by the relentless, massive burning of fossil fuels. In thinking about these questions, I have been guided by Auguste Comte’s incredibly astute observation that “we seek to know in order to foresee and to foresee in order to control.”

What Is and Will Be the Case?

What we know in general, according to physicist Myles Allen, is that “there is a simple and predictable relationship between the total amount of carbon injected into the atmosphere and peak projected warmings. Releasing a trillion metric tons of carbon [or 3 trillion tons of CO2] into the atmosphere may cause a most likely peak warming of two degrees Celsius or 3.6 degrees Fahrenheit, which many identify as a danger.”14 What we know specifically, according to Bill McKibben and others, is that since the start of the industrial revolution in 1750, we have released, as of 2011, 531 billion metric tons of carbon into the atmosphere by burning fossil fuels, primarily coal. At current rates of release, we will put enough carbon into the air to raise the global temperature by a very disruptive 1.5 °C in about six years, and we will burn the remainder of our “carbon budget,” which has been reduced by now (July, 2016) to only about 330 billion tons of carbon (or 1000 gigatons of CO2), in another 15 to 20 years.15 At that point, around 2034, we will have warmed the planet a catastrophic 2 °C or more above the preindustrial level, and an average global temperature of 61.5 °F or higher will be the hellish, “new normal.” Not to alarm you too much, but this July was not only the hottest July on record but the hottest month since 1880, with an average global land/ocean surface temperature of 16.67 °C or 62.01 °F, which was, according to NOAA, 1.57 °F above the twentieth-century average of 60.44 °F and 4.41 °F above the preindustrial average.16

At the beginning of the industrial revolution, there were 270 to 280 ppm of CO2 in the atmosphere; then 315 in 1959; 379 in 2005; 386 in 2010; 396 in 2013; 401 in 2015; and 403 to 407 in 2016.17 We are now adding 2.25 ppm of CO2 a year to our air and the average global temperature actually reached 61.52 F or 16.4 °C in June, 2016, breaking the 2 °C hotter threshold for the first time, according to NOAA. If this trend continues, we will hit 450 ppm of CO2 in less than twenty years, the average global temperature will be perhaps as much as 3 °C hotter than baseline averages and we will be royally, hellishly f**ked by climate change or rather the drastic, almost unimaginable consequences of that process.

According to reports that are readily available on the net by NASA, NOAA, Climate Central, the EPA and similar agencies and organizations,18 over the last 50 years the average global temperature has increased at the fastest rate in recorded history. Every year for the last 40 years has been warmer than the average global temperature for the twentieth century. Fifteen of the sixteen hottest years on record have occurred since 2000. The year 2015 was by far the warmest on record since 1880 and there is a 99 percent chance that 2016 will be warmer than 2015. The first six months of 2016 were the warmest six-month period on record and were 2.7 °F warmer than the pre-industrial average. Each month in 2016 exceeded all previous average temperature records for that month. June 2016 was the fourteenth straight hottest month on record and July was the fifteenth. For the first time in recorded history, the average global temperature of the earth in 2015 was 1 °C above the preindustrial average. Another 1 °C increase in average temperature or a sustained 2 °C above the preindustrial average will produce catastrophic climate change. Previous forecasts that we will hit that by 2034 now seem rather optimistic and if we continue to practice business as usual and these trends continue, we will probably have put more than 600 ppm of CO2 in the atmosphere by the end of the century, the global average temperature will be 4 to 10 °C hotter than the average temperature in which we evolved as a species, and our great grandchildren will be burning in a hellish, striated, Hobbesian world and cursing us for our incredibly immoral selfishness.

As the average global temperature moves permanently beyond roughly 16 °C or 62 °F, we can expect to see an even more rapid, unstoppable melting of the Greenland and West Antarctica ice sheets, an appreciable sea-level rise, destructive warming and acidification of the oceans, massive storm surges, the inundation of coastal cities around the world, the disappearance of small island states, increases in allergies, asthma and infectious diseases, drastic declines in potable water, food fish and agricultural production, the unabated mass extinction of other species, and the proliferation of extreme weather events, such as relentless, murderous heat waves, sustained droughts and frequent torrential rains, more powerful hurricanes and tornadoes, and all this will, I think you must quickly realize, exacerbate a plethora of other social and political problems.19 Eventually, if these trends continue deep into the next century, a kind of “end-of-days” apocalypse could occur in which world trade collapses, democratic governments start to disappear, nation states fragment, war and ethnic strife become endemic, and civilization, as we know it, disintegrates.20 Indeed, at some point in the foreseeable future, the disastrous direct and indirect consequences of unmitigated climate change will destroy the institutional capacity of the human species to respond coherently and effectively to climate change and then our progeny will really be royally and hellishly f**ked.

In April global leaders met in New York to sign the Paris climate agreement, which had been approved on December 12, 2015 by 195 nations at the twenty-first meeting of the UN-sponsored Conference of Parties (concerned about climate change). The agreement committed virtually all the countries in the world to “holding the increase in global average temperature well below 2 °C above preindustrial levels and pursuing efforts to limit the temperature increase to 1.5 °C.” Unfortunately, the average global temperature of the first three months of this year has already almost hit that 1.5 °C threshold, and it now appears that even if there is no free riding and each of the 195 countries meets its proposed emission-reduction goal, their collective total emissions of CO2 will not decline significantly and by 2050 the global average temperature will be at least 3 °C higher than the preindustrial average. In other words, while the nations of the world were willing to sign a nonbinding agreement to do something meaningful about climate change, most were individually and practically unwilling to do enough work, to sacrifice enough for the common good, to accomplish the goal. Concretely if all the nations that endorsed the Paris Accord hit their “Intended Nationally Determined Contributions” (i.e. proposed reductions), CO2 and other greenhouse gas emissions would only drop from 60 billion metric tons today to 54 billion in 2030, which clearly would not do much to slow the buildup of CO2 and the pace and magnitude of climate change.21 For all of President Obama’s good intentions, the United States has only pledged to drop its emissions 28 percent below its 2005 level (7.1 gigatons) by 2025 or only about 2 billion tons below its current level of 7.5 gigatons. And this ignores the fact that the US plans in this span to burn more natural gas and thus emit more methane, which actually captures and reradiates more heat per molecule than CO2. All this provides simultaneously an example of the problem of collective action and “the environmental policy paradox,” described by Professor Zach Smith as a recurring and puzzling condition in which policy makers seem to understand what to do about an environmental problem, like climate change, but fail, for various reasons, to respond to it in a timely and effective manner.22

Donald Trump has called climate change “bullshit” and a “hoax” perpetuated by the Chinese to weaken America, and recent polls indicate that a majority of Republicans basically agree with him.23 Thus it is no surprise that the platform just approved by the GOP at its convention explicitly rejects the imposition of a carbon tax and calls for rescinding Obama’s Clean Power Plan and withdrawing from the Paris Climate Accord, which the United States signed in April and agreed in September to participate in formally, in conjunction with a similar commitment from China.24 Trump, of course, did not mention climate change in his Nomination Speech at the Convention, and one editorial observed that the “GOP Fiddles While America Burns.”25 In contrast, the Democratic platform characterized climate change as “an urgent threat and a defining challenge of our time,” and called for putting a tax on carbon. But alas, Hillary Clinton had only two tepid sentences about this “urgent threat” in her Nomination Speech: “I believe in science. I believe that climate change is real and that we can save our planet while creating millions of good-paying clean energy jobs.”26 Someday, I think, conditions will force the presidential candidates of both major parties to talk at great length about their plans for dealing with climate change. I just hope that this happens before it is way too late, before water from the D.C. tidal basin is lapping at Jefferson’s feet in his Memorial.

What Ought to Be the Case?

Ideally, the global economy will be substantially “decarbonized” by 2050 and certainly before 2100,27 emitting roughly 12 billion metric tons of carbon dioxide equivalents per year by midcentury and fueled then primarily by wind, solar, water, geothermal and, although I hate to say it, a lot of nuclear power, generated perhaps by fast-fusion reactors. The concentration of CO2 in the atmosphere, instead of hurtling toward 450 ppm and beyond as it currently is, will be moving back toward 350 ppm, as the great climatologist James Hansen has contended is necessary to have real sustainability.28 This will mean that not only will the burning of fossil fuels virtually cease by 2085 but, according to a new study by the National Center for Atmospheric Research, technologies must be in place by then that extract 15 billion tons of CO2 from the air each year, so that we actually have “negative emissions.” 29 The population of the earth will be stabilized at less than nine billion and we will have zero population growth in the future. People will lead much greener, less consumptive, more energy efficient lives. They will walk and bike more, play more tennis and other sports, watch a lot less TV, use public transportation a lot more, drive small, energy efficient cars, and eat little or no meat, whose production now contributes significantly to climate change. 30 The United States, among many other things, will have an extensive high speed rail system and scores of new, small nuclear power plants.

The American political system will be fixed, so that it can actually get things done. It will no longer be what Francis Fukuyama now describes as a gridlocked “vetocracy,” suffering from “a problem of political decay in a more acute form than other democratic political systems.”31 Virtually all the nations in the world will be strong, robust democracies, the UN will be strengthened, and there will be powerful regulatory agencies at the national, regional and international levels to control the emission of greenhouse gases, to deal with a myriad of other environmental problems, to administer a carbon tax and to direct a massive program to develop clean forms of energy, more efficient technologies and on and on.

Crucially, and I mean crucially, virtually everyone will realize that, like the earth revolving around the sun, anthropogenic climate change is not a hoax, but a scientifically established fact, that the burning of fossil fuels since the industrial revolution has contributed substantially to the growing concentration of CO2 and other greenhouse gases in the atmosphere and thus to the warming of the planet, and that everything possible must be done to reverse this process, including paying a very stiff carbon tax.

Of course, it goes without saying that none of this may come to pass and that we will instead be living in an extremely hot, ugly, FUBARed world.

What Should Be Done to Get There from Here?

To ensure that our nation and the world community has a decent, sustainable future, the United States should become the clear, unquestioned leader in the global effort to combat climate change, to stabilize the average global temperature at less than 62 °F or something short of 2 °C above the preindustrial level. And to achieve this goal the United States should, among many other measures, impose on itself a carbon tax of $80 dollars per metric ton by 2020 and champion the creation of a global carbon tax, which will work to reduce the burning of fossil fuel, encourage the development and use of renewables and promote technological innovations to enhance energy efficiency and the attractiveness of alternative fuels.32 The funds collected through the carbon tax should be used in part to cushion the impact of the tax on the less advantaged members of society, to provide incentives for the development and deployment of green technologies and renewable energy, and to help developing countries transition to a decarbonized future. Critically, the Paris Climate Accord must be strengthened significantly, with participating countries agreeing by 2020 to raise their “Intended Nationally Determined Contributions” (proposed reductions in CO2 emissions) dramatically enough to actually hold “the increase in global average temperature well below 2 °C.” And then they must abide by their new pledges.

For all this to happen, to stop just fiddling while we burn, at least two critical things must occur. First, the American political system must be fixed so that polices promoting decarbonization can be enacted. Big money must be taken out of our politics, the gerrymandering of our congressional districts must be reversed, and the filibuster rule in the Senate must be eliminated or reformed. Second, the ideological polarization about climate change must come to end. To put it simply, to avoid being unbelievably f**ked by climate change, the preponderant majority of people in this country and indeed the world must come to accept, sooner rather than later, the wisdom and advice I have sought to distill and convey in my last lecture, which is, in a nutshell, that we are going to be f**ked by climate change unless we take all kinds of actions to drastically reduce and then virtually eliminate the burning of fossil fuels. And it occurs to me that one of those actions would be for more and more professors from the baby boom generation to give last lectures that dwell on the threat of climate change and what can be done to mitigate it. Millions and millions of voices in millions of venues must speak out to change the hearts and minds of billions and billions of people across the globe in order for us to achieve sustainability.

Finally, I want to say that my goal here has not been simply to entertain you, to give you something interesting to think about, to let you experience once again one of my lectures at a pleasant Summer Retreat. I don’t want you to just passively accept my message; I don’t want you to be free riders, hoping others will sacrifice for the common good, while you continue to live high on the hog of fossil fuels, driving an SUV, keeping the AC on high, refusing to vote for anyone who proposes a carbon tax that would initially raise the price of gas perhaps a buck or two a gallon. Instead, as Gandhi said, you must actually “be the change you want to see in the world,” politically, economically, socially, and ecologically. If you want to alleviate the threat of climate change, you’ve got to live a life that helps alleviate the threat of climate change; you’ve got to walk the walk and so do I. As my wife often says to me, “if you’re such a big environmentalist, turn off the lights and TV when you leave the room.”

This is what I hoped I would be able to say in my last lecture, when I started to think about climate change as my topic. But I have to confess, it all sounds, even to me, farfetched, improbable, ridiculously idealistic, if not laughable. On such a nice day it is hard for me to believe, despite what the data say, that the planet has just suffered through the hottest month on record (again, 62.01 °F and 16.67 °C, according to NOAA) and that things will get much, much worse, if the nations of the world don’t cut their CO2 emissions by 80 percent by 2050 and leave 85 percent of the known fossil fuel reserves in the ground forever. It’s hard for me to believe we can do anything like that. It’s hard for me to believe that we, the American people, will fix our politics in the foreseeable future, enact a stiff carbon tax and encourage China, India, the EU and the rest of the world to do the same. And that’s why, in a nutshell, it’s hard for me to believe that we will give up our addiction to oil, coal, and natural gas and avoid being royally, hellishly f**ked by climate change. But again, as I said, that does not have to be our fate. Improbable does not mean impossible, necessary or ineluctable. We don’t have to overdose on fossil fuels. We can get green and clean. We’re not blind and we’re not helpless. We know what is causing climate change; we can foresee its terrible consequences, and we know how to control, reduce and eventually eliminate the use of fossil fuels and to take measures to adapt to the level of warming that is now inevitable, given the CO2 already in our air. We just have to do it. So turn out the lights when you leave the room, join an environmental group or two, and become a passionate advocate of a stiff carbon tax. Start living a much greener, more environmentally sustainable and ecologically moral life. In short, live what is actually the good life for the new millennium. Your kids and their kids will praise you for your wisdom and thank you for your sacrifices for their well-being. That’s the final, practical piece of advice I’d like to give you in this my last lecture, at least for now.

Addendum

As I write this addendum to my last lecture a few days after the 2016 presidential election, I am filled with a mix of conflicting emotions: despair, dread, outrage, exasperation, sadness- but also hope and a resolute determination to fight on, to “Never give in… Never, never, never, never… except to convictions of honour and good sense,” as Churchill declared in 1941 when England was still facing defeat in World War II.

The election of Donald J. Trump as the 45th President of the United States has palpably and exponentially increased the probability that we are going to be royally and hellishly f**ked by climate change in the not too distant future. We have replaced a president, who became an eloquent and effective champion of the environment, who viewed climate change as the greatest long-term threat facing the world, who repeatedly warned that we were not acting fast enough to combat what he called in September its “terrifying trends,”33 with a president who will be, as Michael Brune, the Executive Director of the Sierra Club observed, “literally the only head of state on earth who is a climate-change denier.”34

Before the election, which I expected Hillary Clinton to win, I had become convinced on the basis of a fantastic article by Theda Skocpol and Alexander Hertel-Fernandez35 that “the Koch network,” with its incredible organizational and financial resources, was ideologically and politically the single most powerful force preventing the United States from acting more quickly and effectively to combat climate change. But now I realize that the damage done by Charles and David Koch to the climate will be almost nothing compared to what President Trump is about to do, if he carries out his campaign proposals. In short, instead of helping to reduce the global emissions of CO2 and other greenhouse gases, the Trump administration will be acting to increase their output tremendously. Under President Trump the United States will opt out of the Paris Accord and this in turn will encourage China and then many other countries to withdraw too, perhaps causing the collapse of the whole structure. Even if that doesn’t occur, America’s withdrawal from the agreement will deflate the remaining participating countries and cause them to work less strenuously to fulfill their national pledges. At the same time, President Trump will rescind Obama’s Clean Power Plan and other regulations that curtail American emissions.36 Instead of helping to keep 85 percent of the known fossil fuels reserves underground, the United States will be working overtime to exploit then and thus, of course, encouraging other nations to do the same. As prominent climatologist Michael Mann observed, Trump’s climate policies could mean that it’s “game over” for the planet. Without an effective Paris Accord, Mann argues, there will be nothing the countries of the world can do to prevent the planet’s average temperature from increasing between 4.0 and 4.5 °C by 2100, as a recent scientific paper predicts.37 If the average global temperature at the end of the century is in the mid to high 60s °F, the waters of the D.C. tidal basin could be lapping at Jefferson’s feet in his Memorial, and the world will be a very hellish, FUBARed place.

Why, then, do I have any hope that fighting on, that not giving in to pessimism and despair can make any difference, can help to save the climate and the planet, during the presidency of Donald Trump? Let me give you just three reasons. First, I believe that the climate science on which my last lecture is based is correct and that nature itself will make this increasingly clear. For example, in a remarkable article, entitled “2016’s Hellish Summer Weather: A Told-You-So Moment?,” Seth Borenstein describes the massive flooding around the globe, the droughts and wildfires in California, Canada, China and India, the unrelenting, record- setting heat, and the ten extreme weather disasters that each caused more than a billion in losses and occurred between May and September (and this litany of disasters doesn’t even include Hurricane Matthew). He indicates how these events were related to the effects of climate change, and observes that James Hansen was able to forecast back in 1988 “with a crude computer model” the global temperate rise, the “big changes in the number of days when the overnight temperature would not go below 75 and the daytime highs would exceed 95 in four cities by the 2010s.”38 In another remarkable article, with the title “Flooding of the Coast Caused by Global Warming Has Already Begun” and with the subtitle “Scientists’ Warnings that the Rise of the Sea Would Eventually Imperil the United States’ Coastline Are No Longer Theoretical,” Justin Gillis documents how the rising sea is beginning to inundate and damage towns and cities along the east coast and how elections in those areas are beginning “ to be won or lost on promises to invest money to protect against flooding.”39

My point, again, is that climate scientists have got it mostly right about climate change. They have the theories and forecasting models to predict what is going to happen to our climate as the concentration of CO2 and other greenhouse gases increases and what that will do in turn to other aspects of the biosphere. Citizens who want to do something about climate change should strive to become fully informed about its causes, consequences and remedies. They then need to inform their president, senators and representatives about what they have learned and that their future political support for them depends on their willingness to do something about climate change, even if it is just to invest in green energy projects, including the building of wind farms and nuclear plants. They need to tell their senators to filibuster and refuse to see confirmed any of the President’s nominees for positions in the Cabinet, the EPA and other regulatory agencies, and the judiciary, who are not willing to be at least “pragmatic” about the issue of climate change and the degradation of the environment in general.

This leads me to my second cause for hope that the game is not over for the climate: Donald Trump did not win the popular vote for president. Let me say that again: Donald Trump did not win the popular vote for president. As I write this addendum, Hillary Clinton is leading him in the popular vote by more than almost 2 million votes, and that figure is expected to grow, since the states which have not gotten in all their tallies are large, heavily Democratic states like New York and California. Trump won the presidency because of the quirky way the anachronistic, undemocratic Electoral College “actually counts” the vote for president. Hillary Clinton received more popular votes than any presidential candidate in history, except Barack Obama. In other words, many more people voted for the candidate who said she believed in the science of climate change and wanted to do something about the problem than voted for the candidate who said that climate change was a hoax. This makes me hopeful. If Mr. Trump had won the popular vote, that would have been a cause for serious despair. But he didn’t, and four years from now he could be even more vulnerable on the issue of climate change and he should be reminded about that as often as possible.

Finally, I have hope not only because I believe that the science of climate change is valid and that nature will confirm its truth over and over in increasingly uncomfortable and undeniable ways, but also because I believe that fighting to stabilize the climate and save the planet is the morally right, just and laudable thing to do. So, as I said at the end of my last lecture, be the change you want to see in the world; turn off the lights and TV when you leave the room; join an environmental group or two; become a passionate advocate of a stiff carbon tax. And please, especially during the presidency of Donald Trump, don’t be afraid to exercise your First Amendment rights. Write letters to the editor; petition your government; assemble, march, speak truth to power about climate change and the pressing need to do something about it now, before we are royally, hellishly, f**ked by it.

After writing that last sentence less than two weeks ago, I was stunned to learn that Donald Trump had declared, on November 22, during an interviews with Thomas Friedman and other New York Times columnists, that: (1) he has an “open mind” about and is “going to look very carefully [at]” the whole issue of climate change, the Paris agreement and whether America would continue to play a leading role in confronting climate change; (2) he views “clean air” and “clean water, crystal clean water… as vitally important;” (3) he actually thinks “there is some connectivity” between human activity and climate change, but (4) he doesn’t know “how much” and is concerned about “how much it’s going to cost our companies” to do something about the climate issue.40 For me, all this is incredibly good news. It means that Donald Trump is not an implacable climate-change denier, that he is open to reason and evidence, and that he can be educated about how dealing with climate change, despite its costs, can yield enormous economic benefits and is absolutely vital to the health and well-being of American companies, their workers, and indeed the human species. It means that we can now have a bit more hope that, even during the Trump presidency, things can be accomplished that will help to save the climate and the planet, if we hold his feet to the fire and fight on. But, alas, I must leave you with a sobering thought, a last piece of wisdom, provided recently by Dr. Michael Mann on his blog. Even if Hillary Clinton had won the presidency, the United States would have been emitting approximately five to six gigatons of CO2 per year in 2020 (in contrast to the seven gigatons or so then if Trump were to fulfill his campaign proposals), and, combined with the roughly 40 gigatons released by the other nations, we would have warmed the climate a “very disruptive” 1.5 °C in just four to six years. In other words, as Dr. Mann adroitly put it, “the future of the global climate would have been fracked even had the election gone the other way,” unless a Clinton administration had undertaken almost immediately “stronger action to cut CO2 emissions” than expected.41 With the global temperature currently at 1.2 °C above the preindustrial average, it seems inevitable now that in very short order we will see a climate that is at least 1.5 °C warmer than it was only a hundred years ago. Somehow we’ve got to do more, so much more to avoid hitting in turn a catastrophic 2 °C hotter in 2034, 3 °C in 2050 and 4 °C near the end of the century, at which point the Trump National Doral Golf Club in Miami will be as much as six feet underwater, according to an estimate by the Southeast Florida Regional Climate Change Compact,42 and we will be “irrevocably fracked,” FUBARed, f**ked, royally and hellishly.

That said, I want to end my last lecture by reaffirming its thesis: although we are probably going to be f**ked good and hard by climate change, that does not have to be our fate, if we can take the tough, requisite actions to break our addiction to fossil fuels sooner rather than later. And right now, as I see it, this means, among a whole panoply of other actions, reminding President Trump, his administration and supporters in Congress over and over about what science says about climate change and its causes, consequences and remedies, and asking them again and again if they want to be remembered by future generations as politicians who, seduced by the love of power and the lure of campaign contributions, simply ignored or actively abetted an impending planetary holocaust.

End Notes

1.^ This essay is a reconstruction of the “last lecture” I delivered on July 31, 2016 at the inaugural Westminster College Summer Retreat in Fulton, Missouri for alumni, faculty and students. It was written shortly after the lecture and is largely based on the dense outline I prepared for the talk and distributed to the audience. The essay retains the title, overall structure, conversational style, and much of the substance of the lecture as delivered. Like the spoken lecture, this essay is intended for a general audience of educated people, and thus I have used mostly popular sources, which can be easily found through Google, to support my claims. I have not rewritten the main body of the essay to reflect developments that occurred after July 2016, but I do cite sources published since then. I have added an addendum that discusses how the election of Donald Trump as the 45th President of the United States bears on the argument of my last lecture.

2.^ Catherine Gautier, “How Climate Change is Making California’s Epic Drought Worse,” The Conversation, May 21, 2015.

3.^ James Hansen, “The Threat to the Planet,” The New York Review of Books,” July 13, 2006; Laurence C. Smith, “Greenhouse Warming: Prepare for the Worst, The New York Review of Books, 63, no. 15 (Oct. 2016), 44–46.

4.^ For excellent overviews of climate change, its deleterious consequences and what can be done to alleviate them see Justin Gillis, “Short Answers to Hard Questions About Climate Change,” The New York Times, November 25, 2015; Justin Gillis, “Panel’s Warning on Climate Risk: Worst is Yet to Come,” The New York Times. March 31, 2014; Naomi Klein, This Changes Everything. New York: Simon and Schuster, 2014, 1–28.

5.^ FUBAR is an acronym for the military slang term “f**ked up beyond all recognition” that became popular during WWII.

6.^ Brad Werner, “Is Earth F**ked? Dynamical Futility of Global Environmental Management and Possibilities for Sustainability via Direct Action Activism,” December 6, 2012; Dave Levitan, “After Extensive Mathematical Modeling, Scientist declares ‘Earth is F**ked’,” io9 Gizmodo, December 7, 2012. Werner’s argument and presentation of his unpublished paper is discussed by Naomi Klein, in This Changes Everything, 449–450.

7.^ Francis MacDonald Cornford, The Republic of Plato. New York: Oxford University Press, 1986, 121.

8.^ “Climate Change 2007: Synthesis Report,” IPCC Fourth Assessment Report: Climate Change 2007, Topic 5: The long term perspective: 64–70; Brian Mastroianni, “Why 2 Degrees Are So Important to Climate Change,” CBS News, November 30, 2015.

9.^ The greenhouse gases countries are now emitting contain about 60 billion metric tons of carbon dioxide-equivalents. See Bobby Magill, “Negative Emissions Key to Meeting 2°C Threshold,” Climate Central, July 12, 2016.

10.^ James Ayre, “Study: Limiting Global Warming to Under 2 °Celsius Requires Ceasing Emissions by 2085 AND Technology to Remove Carbon From Atmosphere,” CleanTechnica, July 26, 2016.

11.^ R.L. Miller, “Climate Change Report Supports Bill McKibben’s ‘Terrifying New Math’.” Take Part, September 28, 2013.

12.^ Al Gore, “The Turning Point: New Hope for the Climate,” Rolling Stone, June, 18, 2014.

13.^ Carl Husle and Julie Hirschfield Davis, “Obama’s Plea to ‘Fix Our Politics’ Leaves Both Sides Looking Inward,” The New York Times, January 13, 2016.

14.^ Quoted in David Biello “How Much Is Too Much? Estimating Greenhouse Gas Emissions.” Scientific American, April 29, 2009.

15.^ Bill McKibben, “Global Warming’s Terrifying New Math,” Rolling Stone, July 19, 2012; I have used R.L. Miller’s recalculations of McKibben’s terrifying math in light of a more recent report by the Intergovernmental Panel on Climate Change.

16.^ NOAA National Centers for Environmental Information, State of the Climate: Global Analysis for July 2016, published online August 2016, retrieved on November 12, 2016.

17.^ Brian Kahn, “The World Passes 400 PPM Threshold. Permanently,” Climate Central, September 27, 2016.

18.^ See, for example, Andrea Thompson, “First Half of 2016 Blows Away Temp Records,” Climate Central, July 19, 2016.

19.^ Rebecca Leber, “This is What Our Hellish World Will Look Like After We Hit the Global Warming Tipping Point,” New Republic, December 21, 2014; Bill McKibben, “Some Like it Hot!” The New York Review of Books. May 9, 2013, 59–60.

20.^ Michael Northcott, A Political Theology of Climate Change. Grand Rapids, Michigan: William B. Eerdmans Publishing Company, 2013, 304.

21.^ John Upton, “Paris Talks Won’t Achieve 2°C Goal: Does That Matter?” Climate Central, February 10, 2015; Bobby Magill, “Negative Emissions Key to Meeting 2°C Threshold,” July 12, 2016.

22.^ Zachary A. Smith, The Environmental Policy Paradox, Sixth Edition, Boston: Pearson, 2013. 92-93, 325.

23.^ Louis Jacobsen, “Yes, Donald Trump Did Call Climate Change a Chinese Hoax,” Politifact. June 3, 2016,.

24.^ James Bruggers, “Party platforms clash on climate change,” courier-journal, July 26, 2016.

25.^ Phil Plait, “The GOP Fiddles While America Burns,” Slate, July 20, 2016.

26.^ “Hillary Clinton’s DNC Speech: Full Text,” CNN Politics, July 28, 2016.

27.^ “’Decarbonization’,” St. Louis Post-Dispatch, December 16, 2015, Opinion Section, A14.

28.^ James Abraham, “What’s Climate Scientist James Hansen’s Legacy?” The Guardian.  April 29, 2013.

29.^ Bobby McGill, “Negative Emissions Key to Meeting 2°C Threshold,” Climate Central, July 12, 2016.

30.^ Bruce Friedrich, “What Would the Pope Eat?” USA Today, September 17, 2015, News Section, 7A.

31.^ Francis Fukuyama, Political Order and Political Decay, New York: Farrar, Straus and Giroux, 2014, 487.

32.^ “Carbon Cure-All,” St. Louis Post-Dispatch, December 27, 2012, Opinion Section, A18.C

33.^ Julie Hirschfeld Davis, Mark Landler and Coral Davenport, “Obama on Climate Change: The Trends are ‘Terrifying’,” The New York Times. September 8, 2016.

34.^ Oliver Milman, “Donald Trump Would Be World’s Only National Leader to Reject Climate Science,” The Guardian, July 12, 2016.

35.^ Theda Skocpol and Alexander Hertel-Fernandez, “The Koch Network and Republican Party Extremism,” Perspectives on Politics 14, no. 3 (September 2016): 681-699. DOI: 10.1017/S1537592716001122.

36.^ Steven Mufson and Brady Dennis, “Trump Victory Reverses U.S. Energy and Environmental Priorities,” The Washington Post, November 9, 2016.

37.^ Chris Sommerfeldt, “Donald Trump’s Climate Policies Could Mean Game Over for the Planet: Scientist,” New York Daily News, November 10, 2016.

38.^ Seth Borenstein, “2016’s Hellish Summer Weather: A Told-You-So Moment?” St. Louis Post-Dispatch, September 21, 2016, Nation Section, A4.

39.^ Justin Gillis, “Flooding of the Coast Caused by Global Warming Has Already Begun,” The New York Times, September 3, 2016

40.^ The New York Times, “Donald Trump’s New York Times Interview: Full Transcript,” November 23, 2016

41.^ Michael Mann, “Trump Carbon and the Paris Agreement,” Real Climate, November 17, 2016.

42.^ The Editors, “Trump and the Planet,” St. Louis Post-Dispatch, November 28, 2016. AO9

Bibliography

Abraham, James. “What’s Climate Scientist James Hansen’s Legacy?” The Guardian. April 29, 2013.

Ayre, James. “Study: Limiting Global Warming to Under 2°Celsius Requires Ceasing Emissions by 2085 AND Technology to Remove Carbon From Atmosphere.” CleanTechnica. July 26, 2016.

Biello, David. “How Much Is Too Much? Estimating Greenhouse Gas Emissions.” Scientific American. April 29, 2009.

Borenstein, Seth. “2016’s Hellish Summer Weather: A Told-You-So Moment?” St. Louis Post-Dispatch. September 21, 2016, Nation Section, A4.

Bruggers, James. “Party Platforms Clash on Climate Change.” Courier Journal. July 26, 2016.

“Carbon Cure-All.” St. Louis Post-Dispatch. December 27, 2012, Opinion Section, A18.

“Climate Change 2007: Synthesis Report.” IPCC Fourth Assessment Report: Climate Change 2007. Topic 5: The long term perspective: 64–70.

Clinton, Hillary. “Hillary Clinton’s DNC Speech: Full Text.” CNN Politics. July 28, 2016.

Cornford, Francis MacDonald. The Republic of Plato. New York: Oxford University Press, 1986.

Davis, Julie Hirschfeld, Mark Landler and Coral Davenport. “Obama on Climate Change: The Trends are ‘Terrifying’.” The New York Times. September 8, 2016.

“’Decarbonization’.” St. Louis Post-Dispatch. December 16, 2015, Opinion Section, A14.

Friedrich, Bruce. “What Would the Pope Eat?” USA Today. September 17, 2015, News Section, 7A.

Fukuyama, Francis. Political Order and Political Decay. New York: Farrar, Straus and Giroux, 2014.

Gautier, Catherine. “How Climate Change Is Making California’s Epic Drought Worse.” The Conversation. May 21, 2015.

Gillis, Justin. “Flooding of the Coast Caused by Global Warming Has Already Begun.” The New York Times. September 3, 2016.

Gillis, Justin. “Panel’s Warning on Climate Risk: Worst Is Yet to Come.” The New York Times. March 31, 2014.

Gillis, Justin. “Short Answers to Hard Questions About Climate Change.” The New York Times, November 25, 2015.

Gore, Al. “The Turning Point: New Hope for the Climate.” Rolling Stone. June 18, 2014.

Hansen, Jim. “The Threat to the Planet.” The New York Review of Books. July 13, 2006.

Husle, Carl and Julie Hirschfield Davis. “Obama’s Plea to ‘Fix Our Politics’ Leaves Both Sides Looking Inward.” The New York Times. January 13, 2016.

Jacobsen, Louis. “Yes, Donald Trump Did Call Climate Change a Chinese Hoax.” Politifact. June 3, 2016.

Kahn, Brian. “The World Passes 400 PPM Threshold. Permanently.” Climate Central. September 27, 2016.

Klein, Naomi. This Changes Everything. New York: Simon & Schuster, 2014.

Leber, Rebecca. “This is What Our Hellish World Will Look like after We Hit the Global Warming Tipping Point.” New Republic. December 21, 2014.

Levitan, Dave. “After Extensive Mathematical Modeling, Scientist declares ‘Earth is F**ked’.” io9 Gizmodo. December 7, 2012.

Magill, Bobby. “Negative Emissions Key to Meeting 2°C Threshold.” Climate Central. July 12, 2016.

Mann, Michael. “Trump Carbon and the Paris Agreement.” Real Climate. November 17, 2016.

Mastroianni, Brian. “Why 2 Degrees Are So Important to Climate Change.” CBS News. November 30, 2015.

McKibben, Bill. “Global Warming’s Terrifying New Math.” Rolling Stone. July 19, 2012.

McKibben, Bill. “Some Like it Hot!” The New York Review of Books. May 9, 2013, 59-60.

Miller, R. L. “Climate Change Report Supports Bill McKibben’s ‘Terrifying New Math’.” TakePart. September 28, 2013.

Milman, Oliver. “Donald Trump Would Be World’s Only National Leader to Reject Climate Science.” The Guardian. July 12, 2016.

Mufson, Steven and Brady Dennis. “Trump Victory Reverses U.S. Energy and Environmental Priorities.” The Washington Post. November 9, 2016.

The New York Times. “Donald Trump’s New York Times Interview: Full Transcript.” The New York Times.

NOAA National Centers for Environmental Information. State of the Climate: Global Analysis for July 2016, published online August 2016. Retrieved on November 12, 2016.

Northcott, Michael. A Political Theology of Climate Change. Grand Rapids, Michigan: William B. Eerdmans Publishing Company, 2013.

Plait, Phil. “The GOP Fiddles While America Burns.” Slate. July 20, 2016.

Skocpol, Theda and Alexander Hertel-Fernandez. “The Koch Network and Republican Party Extremism.” Perspectives on Politics 14, no. 3 (September 2016): 681–699. DOI:10.1017/S1537592716001122.

Smith, Laurence C. “Greenhouse Warming: Prepare for the Worst.” The New York Review of Books. October 13, 2016, 44–46.

Smith. Zachary. The Environmental Policy Paradox. Sixth Edition. Boston: Pearson, 2013.

Sommerfeldt, Chris. “Donald Trump’s Climate Policies Could Mean Game Over for the Planet: Scientists.” New York Daily News. November 10, 2016.

Thompson, Andrea. “First Half of 2016 Blows Away Temp Records.” Climate Central. July 19, 2016.

“Trump and the Planet,” St. Louis Post-Dispatch. November 28, 2016, Opinion Section. AO9.

Upton, John. “Paris Talks Won’t Achieve 2°C Goal: Does That Matter?” Climate Central. February 10, 2015.

Werner, Brad. “Is Earth F**ked? Dynamical Futility of Global Environmental Management and Possibilities for Sustainability via Direct Action Activism.” December 6, 2012.

Life and Global Climate Change on Earth

Mark Puckett, Ph. D.
University of North Alabama

Introduction

The history of life on Planet Earth, fueled by the solar radiation in which it has bathed throughout the eons of geologic time, records great periods of richness and the evolutionary appearance of an incredible diversity of life forms, punctuated by short intervals of wholesale destruction and partial collapses of the biosphere. Many of these destructive events are related to carbon and its exchange between reservoirs in the ground, (magmatic sources and from the shallow burial of organic matter that is life’s debris) and in the atmosphere and oceans. This scenario is happening today as the combined effects of the human burning of fossil fuels is transferring bulk amounts of carbon from the earth into the atmosphere. The exchange (that is, the flux of carbon between the earth and the atmosphere and its effects on life) can be readily determined by observing the ratio of two types of carbon, carbon-12 and carbon-131. Plants preferentially uptake the lighter carbon during photosynthesis and the formation of their sugars and large organic molecules (Fig. 1). During times of abundant burial of plants such as the Pennsylvanian Period, the remains of great ancient forests were buried in the ground where we get most of our coal from today, the relative amount of carbon-12 in the atmosphere decreases, shifting the carbon-12/13 ratio toward the heavier side. The removal of carbon-12 from the atmosphere indicates that there was less carbon in the form of greenhouses gases, which cooled the planet. Shifts of other isotopes, such as oxygen2, show that the reduction in the relative amount of carbon-12 is associated with a decrease in temperature. The opposite situation is also true, with an increase in carbon-12 indicating the influx of more carbon into the atmosphere and strengthening of the greenhouse effect and resulting in warmer temperatures.

v1n1-puckett-fig1

Figure 1. Carbon stable isotope ratios of various carbon-based substances. 3 All plants are enriched in d12C, so burial of plant material causes a reduction in the relative amount of d12C and consequent increase in the relative amount of d13C in the rock record. Reduction of the amount of d12C indicates a reduction in the amount of CO2 in the atmosphere, weakening of the greenhouse effect (GE) and global cooling. The reverse is also the case: spikes in the amount of d12C in the rock record indicate the release of CO2, strengthening of the GE and global warming. The light values of methane products on the left are used to define intervals of the release of methane, which is a more powerful greenhouse gas than CO2.

In his classic 1981 paper, Jack Sepkoski4 published data demonstrating that there were five major extinction events during the Phanerozoic (Fig. 2), which is the time since the appearance of hard parts in the record of life about 540 million years ago. His analysis did not include our current human-induced mass extinction, which was not well understood at the time. We are now in the sixth mass extinction that is unprecedented in the history of our planet, one that is more severe than any of the others up to this point and is entirely caused by one species—humans. Our activities have such a global effect that it has ushered in a new epoch of geologic time, the Anthropocene. This paper presents data indicating that five of the six mass extinctions are related to shifts in the carbon isotope ratios of the planet and that there are direct analogues of our current extinction event in the geologic past. The exception is the extinction event that resulted in the demise of the dinosaurs, which appears to have been mainly caused by the effects associated with a meteorite impact. Throughout this essay, please refer to Figure 2 for the timing of the mass extinctions and to Figure 3 for the paleogeographic configurations at the time of the mass extinctions.

v1n1-puckett-fig2

Figure 2. Sepkoski’s (1990) evolutionary faunas, showing the diversity of families of marine fossils, the three evolutionary faunas (plus the taxa not included in those faunas), and the five major extinction events in Earth’s history. Symbols along the bottom of the chart represent geologic time intervals and include, from left to right, the Precambrian, Cambrian, Ordovician, Silurian, Devonian, Carboniferous, Permian, Triassic, Jurassic, Cretaceous, Paleogene and Neogene.

v1n1-puckett-fig3

Figure 3. Global paleogeographic configurations of the continents during the times of mass extinction. Maps redrafted after Blakey5.

Mass Extinctions as Random Events

Throughout the history of life on Earth, there have been many extinction events that have altered the structure of life, most of which were small. However, a few resulted in near-total rearrangement of the types of life that existed; these are termed mass extinctions. Generally, these mass extinctions resulted in the demise of at least 50% of the kinds of life forms on the planet, while one (the end-Permian extinction 251 million years ago) was considerably more devastating than that, causing more than 95% of the species becoming extinct6 and requiring nearly five million years to recover from. There are parallels between that extinction event and our current one, which is a main theme of this paper.

As devastating as the end-Permian extinction event was, humans would not be on Earth without it to remove ancient life forms and replace them with new ones. There are vast intervals of time during which little changes occurred. In north Alabama where I live, for example, the Mississippian rocks (roughly 320 million years old) are richly fossiliferous, with a world-class, distinctive fauna including extremely abundant crinoids, fenestrate bryozoans, productid brachiopods, and others. Several years ago, I had the opportunity to visit the Permian Basin of West Texas and New Mexico and was surprised to see some of the same fossils as in Alabama, although those Permian rocks are about 50 million years younger. This is not to say that there was no extinction or evolution during this time, but there were no whole-scale changes in the types of life forms on the planet. Essentially all of those life forms would become extinct very abruptly a few million years later. The devastating event 65 million years ago that brought to a close the age of dinosaurs (and many other highly-evolved animals) allowed for the evolution of mammals, which had been around for more than 140 million years, to rapidly diversify. Thus, the role of extinction in the evolution of life today cannot be overestimated, but in our anthropocentricity, we do not wish for this to happen to humans.

How can we assess the impact of humans on planet Earth? One of the best clues is to look at the carbon cycle, as each of the mass extinctions is associated with changes in the ratios of carbon. Indeed, carbon is a very sensitive indicator of the health of inhabitants on our planet. The arrival of Europeans to North America in 1492 and subsequent population collapse due to diseases, war, enslavement, and famine (which reduced the population from approximately 61 million in 1492 to 6 million people by 1650) and the near-cessation of farming and reduction in fire use lowered the atmospheric level of CO2 by 7-10 ppm7.

Understanding the Evidence for Global Climatic Changes

Isotopes

Many of the clues to the global extinction events may be related to changes in the composition of the atmosphere, although the precise cause-and-effect relations are far from completely understood. Circulation of the oceans and atmosphere is coupled, so it acts as a system, with fluxes of huge volumes of common compounds such as carbon dioxide and water. Exchange of these compounds takes place not only near the surface of the oceans, but is driven to great heights and depths as one giant circulating machine. Thus rocks deposited on the land or in the sea can reflect the chemical composition of the planet.

Global climatic patterns are directly linked to deep ocean circulation. In our present world, frigid waters near the surface at high latitudes drive deep ocean circulation, with a constant flow of dense, frigid, well-oxygenated water descending into the ocean basins. In the polar regions, warm, deep ocean circulation can weaken or shut down, leading to widespread anoxic conditions, even in shallow areas. Such anoxia can be devastating to life.

Estimates of the condition of the atmosphere in times past are based largely on the relative percentages of two isotopes: carbon and oxygen. In this essay, we will consider only the carbon isotope signal. Isotopes are different forms of the same element, differing only in the numbers of neutrons in the nucleus. Generally, isotopes of the same element have similar chemical properties because they have the same numbers of reactive electrons, but the difference in the number of neutrons makes them of different masses, and this affects the rates of certain important chemical reactions. The amount of each isotope in rocks is compared to the ratio in a globally-agreed standard. The lower-case Greek letter delta, d, symbolizes the atomic mass of a particular substance in reference to this standard, which happens to be, randomly enough, a Late Cretaceous fossil known as Belemnitella americana from the Pee Dee Formation of South Carolina. Oxygen isotopes are extremely useful for certain types of studies, particularly as paleo-thermometers, but the ratios of the two stable (non-radioactive) isotopes (d16O and d18O) can be affected by several factors, including glaciation and salinity, and generally are not used to determine the state of the atmosphere in toto.

Carbon is extremely useful in studying the condition of past atmospheres (Figure 4). The two carbon isotopes used are carbon-12 (d12C) and carbon-13 (d13C), which are measured in ratio. Nearly all of the carbon on Earth is d12C, so only trace amounts of d13C must be measured. High values of d13C are generally considered to be the result of the removal of significant amounts of the lighter isotope (d12C) from the atmosphere, inferring the lowering of the amount of carbon dioxide and cooling of the planet due to the weakening of the greenhouse effect. Elevated levels of the lighter isotope d12C generally indicate raised levels of atmospheric carbon dioxide and a warming interval. Four of the five mass extinction events in geologic time are strongly correlated to changes in the carbon isotope ratio, as is our current mass extinction.

For this essay, the carbon isotope signals have been compiled from a variety of sources and calibrated to the most current global geologic time scale8. All references to dates of geologic phenomena are in reference to this time scale (Fig. 4).

v1n1-puckett-fig4

Figure 4. The relationship between carbon isotopes and global temperatures.

What Are these Catastrophic Events and What Caused Them?

Late Ordovician Catastrophe

The beginnings of the kinds of life forms we are familiar with emerged slightly over 540 million years ago, and thus began the Phanerozoic Eon, the age of abundant life. The first period of the Phanerozoic was the Cambrian, during which many bizarre kinds of animals appeared then disappeared in the sea, never to be seen again. When the Ordovician began, about 488 million years ago, marine life began the greatest climb in diversity in Earth’s history. Within a few million years, the seas came alive with great reefs, swimming animals and predators, and ancestors of stocks that would last for hundreds of millions of years.

After the initial burst in diversification, a stasis was reached (Fig. 2). Life had reached a plateau in diversity and changed little for millions of years. Then, quite abruptly at the end of the Ordovician about 445 million years ago, there were major perturbations in the Earth system that brought much cooler waters to the low latitudes, formed glaciers, lowered sea level, and killed many of the kinds of life adapted to the warm climates that had prevailed. The specific cause of both the rapid cooling event and the equally rapid return to warm conditions is not well understood, although it is clear that there were major shifts in atmospheric carbon isotope ratios (Fig. 5) that seem to indicate a reduction in carbon dioxide in the atmosphere (note the increase in d13C, which indicates a reduction in d12C, which in turn indicates a reduction in atmospheric CO2). Many workers consider that glaciation was caused by the southern continents (Gondwana) moving over the South Pole9, resulting in global cooling and a drop in sea level. Whatever the cause, the planetary shocks lasted perhaps half a million years and not only eliminated 60 percent of the invertebrate fauna, but cleared the way for new forms to evolve. These changes were significant enough to mark the end of a major period in Earth’s history. The end-Ordovician event is the second most severe mass extinction in geologic time.

v1n1-puckett-fig5

Figure 5. These carbon isotope data, collected from strata exposed in Nevada, indicate a major reduction in atmospheric carbon dioxide and weakening of the greenhouse effect10.

Late Devonian Catastrophe

The Late Devonian extinction event (around 374 million years ago) is unusual in that the Devonian-Mississippian boundary is not placed at the event itself but at the end of the epoch after the event. All of the other extinction events, quite logically, define boundaries between major geologic time periods. It was hardly an “event,” as life declined over some three million years. Many life forms, including giant reef builders, were hit so hard they never recovered, although many squeaked by for another 200 million years before succumbing to the end-Paleozoic extinctions.

The record of carbon and oxygen isotopes reveals the most fascinating part of the Late Devonian catastrophe: the close coupling of the atmospheric, oceanic, geologic, and biologic systems on Earth. Major perturbations occur almost synchronously in carbon (Fig. 6) and oxygen isotopes in the stratigraphic record. A heavier d13C ratio indicates burial of substantial amounts of carbon (and presumably lowering of atmospheric carbon dioxide) and an abrupt shift to shallower water conditions, all occurring at the same time. Viewed as a system, it seems clear that the lowering of atmospheric levels of carbon dioxide is linked to colder water conditions and the drop of sea level, because of the growth of glaciers associated with the colder conditions. (Note: Although glaciers are not generally shown on paleogeographic maps, Late Devonian glacial deposits are known to exist in many parts of the world, particularly in South America, which was over the South Pole during the Late Devonian.)

v1n1-puckett-fig6

Figure 6. Shifts in carbon isotope values during the end-Ordovician extinction event collected from samples in Germany11.

Many Earth scientists think it is no coincidence that these global perturbations are related to the emergence of land plants. For more than four billion years, the land surfaces of Earth were barren until the evolution of plants that appeared in the Silurian that were capable of piping nutrients and water through a vascular system from the ground. By the Late Devonian, these earliest vascular plants had grown to the size of trees, and giant forests spread out over the land surface unrestrained. It is thought that the spread of land plants increased the rates of weathering of rocks on the continents, which requires copious use of atmospheric carbon dioxide. So, in this scenario, the evolution of land plants caused greatly increased rates of erosion of continental rocks, that caused the lowering of carbon dioxide in the atmosphere, that caused colder water conditions in the oceans, that caused the buildup of glaciers, that caused the lowering of sea level, that caused the mass extinctions. The precise cause-and-effect triggers are, however, far from understood, as they are even for the relatively recent Pleistocene glaciations.

Permian-Triassic Catastrophe

Now we come to the greatest catastrophe in Earth’s geologic history, the end-Permian extinction, also known as “The Great Dying.” This event is also the most closely allied to the changes being brought about by human activity. The most disturbing part is that human-caused changes to the planet are occurring at a faster rate than that which occurred at the end of the Permian. Further, it appears that the initial loading of the atmosphere by CO2 lasted a relatively short time interval, but was followed by a cascading series of events that lasted for millions of years. In a geological blink of an eye, 96 percent of marine species and 70 percent of land species disappeared.

It has long been known that the end-Permian extinction was accompanied by major shifts in both carbon and oxygen isotopes, with carbon ratios becoming very enriched in d12C (indicating the release of massive amounts of CO2 and probably methane) into the atmosphere and oxygen ratios becoming enriched in the lighter isotope d16O (indicating global warming)12,13,14,15 (Figure 7). The tough part was to refine the time resolution of the sequence of events in both the marine and non-marine realms, which is not an easy task given that the events occurred about a quarter of a billion years ago. Recent information, particularly from researchers at MIT working in geologic sections in China, has clarified what happened.

v1n1-puckett-fig7

Figure 7. Carbon isotope shifts associated with the end-Permian extinction events16. Ma is mega-annum (millions of years), PTB is Permian-Triassic Boundary, Ccarb is inorganic carbon and Corg is organic carbon. Note that the spike in organic carbon occurred after the negative spike in d12C, demonstrating that the release of massive amounts of d12C later trigger mass death.

Slightly more than 252 million years ago and about 300,000 years before the main extinction event, gigantic, explosive volcanic eruptions occurred in Siberia. The total volume of eruptions and intrusions is almost unimaginable, it being enough to cover the United States in kilometer-deep magma17. These volcanic rocks are known as the Siberia Traps. Most unfortunately for life on Earth, this magmatic activity erupted through massive carboniferous coal deposits (the same ones we burn today in our coal-fired power plants) and ignited them. This combustion loaded the atmosphere and oceans with isotopically light CO2 from the burning of the plant debris and heavy metals from the fly ash. Estimates of this event indicate that it spanned only 20,000 years18, but led to a catastrophic sequence of events.

The first effect was a dramatic and sudden warming of the atmosphere by at least 10°C19 due to the greenhouse effect associated with the injection of massive amounts of CO2 into the atmosphere. The world’s ocean (there was one main ocean at that time due to almost all of the continents being together in the supercontinent Pangea) became acidified due to absorption of CO2. The increased atmospheric temperature caused the ocean in the polar regions to warm considerably, which eliminated the downwelling of cold, oxygen-rich water, shutting down global oceanic circulation and causing stagnation. As the vast amount of dead organisms rotted, aerobic microbes consumed the organic debris, but during this respiration process, oxygen quickly became depleted in the ocean and it became anoxic, leading to the proliferation of sulfate-reducing bacteria and the release of massive amounts of hydrogen sulfide into the atmosphere20. During the oxidation process, oxygen was used up and the level of oxygen in the atmosphere also plummeted21. The increased atmospheric temperatures caused increased rainfall due to high levels of oceanic evaporation, but this rain was more acidic than before because it combined with the high levels of CO2 in the atmosphere. This acidic rain caused increased weathering of rocks at the surface, which sent more nutrients into the ocean, that fed explosions of life such as algal blooms, the decay of which accelerated the depletion of oxygen22. Evidence from Canada, which was downwind from the Siberian eruptions, indicate loading of the world’s ocean by heavy metals from the fly ash created during combustion of the coal23, which further poisoned the already stinking marine environment. In summary, it appears that an initial rapid and massive loading of the atmosphere CO2 caused a poisoning of the ocean and atmosphere that killed most of the living organisms on both the land and in the sea, which led to further deteriorating conditions that lasted for millions of years.

If all of these factors were the result of an initial, powerful injection of CO2 into the atmosphere caused by the burning of fossil fuels, then we can expect a similar Earth response to occur by continued burning of fossil fuels by humans.

Triassic-Jurassic Catastrophe

The Triassic-Jurassic extinction event is perhaps the most difficult one for most people to get their heads around, for several of the groups that were wiped out are not familiar to most of us and it’s difficult to assess the significance. One of these groups is the conodonts, which are one of the most important fossils for dating the Paleozoic extinctions. In almost all cases, these remains consist only of a set of tiny teeth that belonged to small, wormy-looking predators that had existed for hundreds of millions of years. Another group that became extinct is called therapsids, which were generally dog-sized animals that are thought to be the ancestors of all modern mammals. The relation between the therapsids and modern mammals is as enigmatic as the corals described earlier. Although mammals are known to have existed throughout the age of dinosaurs, the bulk of their fossil record consists of small teeth and jaws of tiny animals that lived in the shadows of the dinosaurs and remained an insignificant part of the fossil record.

Perhaps the greatest benefit of the Triassic-Jurassic extinction was to the dinosaurs. After the disappearance of the therapsids, dinosaurs evolved and diversified to become one of Earth’s most spectacular groups of animals, dominating the land biotas for more than 140 million years. The immensity of this length of time is almost incomprehensible, and would have continued if not for the event 65 million years ago.

So what happened? The record of the carbon isotopes (Fig. 8) indicates that there was a major environmental shift very close to 200 million years ago during which massive amounts of light carbon (d12C) were released into the atmosphere, causing major disruptions in both the marine and terrestrial realms. The source of this carbon appears to be associated with one of the major events in Earth’s history: the breakup of the supercontinent of Pangaea and the opening of the Atlantic Ocean, in this case the South Atlantic. This extinction event is relatively short, lasting less than 600,000 years24. If it had not been for this event, there would never have been a T. rex, a velociraptor, or any of the great long-necked dinosaurs—or any of us.

v1n1-puckett-fig8

Figure 8. Carbon isotope shift near the Triassic-Jurassic boundary22.

Cretaceous-Paleogene Catastrophe

Perhaps the best known of the extinctions is the one that killed off the dinosaurs at the end of the Cretaceous Period. The cause of this extinction is now well-established and was the result of a meteorite impact in northwest Yucatán. I have seen the deposits of this event in western Cuba, where hundreds of meters of debris, including building-sized boulders, rained down from the skies. The effects of this event on life are vexing: whereas some groups of organisms that had been around for hundreds of millions of years (dinosaurs and ammonoids, for example) were wiped out forever, other groups were completely unaffected. In any case, if this extinction event had not occurred, if that meteorite had not crossed Earth’s orbit at that exact moment, dinosaurs might still reign supreme.

The Anthropocene

One of the most exciting fields in the geosciences today is the study of the Anthropocene, which is a proposed new epoch of geologic time in which human activity is of global significance. Humans have clearly had a global influence and generally not in a positive way. We have caused massive changes in the distribution of sediment, such as clearing away entire mountains in our search for coal; cleared forests for shipbuilding, farming, pastures, fuel, and many other reasons, all of which has resulted in a change in the stratigraphic distribution of spores and pollen; caused widespread deposition of human-manufactured products such as plastics; nearly completely rearranged the biogeographic distribution of plants and animals; caused mass extinction due to the destruction of habitats, hunting, and many other causes; and transferred massive amounts of carbon and metals from the ground to the atmosphere and oceans, among other global changes. Human activities have released 555 petagrams of carbon25 (where one Pg = 1 billion metric tons, so 555 Pg = 555 billion metric tons), which can clearly be seen in figure 9. (Aside: If 555 billion metric tons of anything were pumped into the atmosphere, we should expect some sort of side effect, much less it being a greenhouse gas.) In figure 9, notice that the values of d13C are decreasing to the right, starting at around 1850 and accelerating until today, which is a reflection of the accelerating influx of d12C from the burning of fossil fuels.

v1n1-puckett-fig9

Figure 9. The amounts of d13C in rocks and reefs deposited during the last 650 years in Jamaica. VPDB refers to Vienna Pee Dee Belemnite, which is a standard for carbon ratios that has been adopted since the exhaustion of the original Pee Dee Belemnite from North Carolina. This figure demonstrates that the increase in CO2 content in the atmosphere is due to human-caused emissions from the burning of fossil fuels.

Another way to look at the influence humans have had on Earth is to look at the natural cycles of glaciation and CO2 through time. Figure 10 shows data collected from the Dome C ice core in Antarctica, with CO2 level peaking at about 280 ppm over the course of the last 800,000 years. The level of CO2 in March 2016 was 404.83 ppm and peaked at 409.34 ppm on April 10, 201626, a level not seen on the planet for millions of years. Projections for future levels, based on a series of scenarios and published by the Intergovernmental Panel on Climate Change, is presented in comparison. At this point, it seems unlikely that the concentration of CO2 will be less than 600 ppm by the end of the century and very well may be 800 ppm, with catastrophic consequences that may last millions of years. Recent calculations show that the greenhouse gas emissions have delayed the next Ice Age by at least 100,000 years27. Certainly, with the extinction of so many species (as many as 100,000 per year28), Earth will never be the same. As the increased concentration of CO2 in the atmosphere and in the rock record is gradual, where exactly do we place the “golden spike?” The questionable placement for the beginning of the Anthropocene based on emissions of greenhouse gases makes it an unlikely criterion.

v1n1-puckett-fig10

Figure 10. Concentration of CO2 during the past 800,000 years based on ice core data. The cycles are driven by orbital cycles called Milankovitch cycles, and include the precession (Earth’s wobble that cycles every 20,000 years), obliquity (which is the amount of wobble and cycles every 41,000 years) and the eccentricity of Earth orbit (cycling from more circular to more elliptical shape every 100,000 years). Note that the concentration of CO2 has not peaked above about 280 parts per million in the past 800,000 years. Data from the top graph taken from http://earthobservatory.nasa.gov/Features/CarbonCycle/page 4.php, and lower graph taken from https://www3.epa.gov/climatechange/science/future.html.

In fact, there are two main contenders for the beginning of the Anthropocene: a significant decrease in the amount of CO2 in the rock record in the year 1610 and a spike in d14C that occurred in 1964 due to the cumulative effects of the testing of atomic bombs, both effects of human activities. The cause of the decrease in atmospheric carbon was noted earlier in this essay, that is, the collision of the Old World and the New World. Europeans had been living in crowded conditions for millennia, catching diseases, passing them to others and building resistance. The Native Americans were generally much more spread out and isolated from the European diseases, foremost of which was smallpox, although there were other diseases such as measles, scarlet fever, typhoid, and influenza. From 1492 until 1650, disease, famine, war and enslavement caused the Native American population to collapse, dropping from 61 million to 6 million people6. This resulted in less farming and fewer fires, both of which tended to transfer CO2 from the air to be buried in the ground. The greatest drop occurred in the year 1610, when the level dropped from what had been a steady average of about 282 ppm to about 272 ppm; the data are primarily derived from two ice cores in Antarctica23. It was during this time interval that the global distribution of plants and animals started to shift, which was also due to human activity, in the Columbian Exchange, which includes almost all of the plants and animals that we eat or use for labor29. The dip in atmospheric carbon is the most prominent feature in pre-industrial atmospheric CO2 records over the past 2000 years30 and is therefore a precise target for the beginning of the Anthropocene.

The other contender is a spike in d14C that occurred as a result of the detonation of atomic devices. In fact, this bellicose activity doubled the amount of d14C in the air31. There are other secondary correlated markers of radioactive elements associated with the bomb testing. These chemical changes are part of The Great Acceleration that began about 1950, in which many socio-economic and Earth systems parameters show a dramatic increase. These parameters include population, fertilizer consumption, water use, CO2, N2O, CH4, marine fish capture, nitrogen to coastal zones, and many others. Although it is clear that the environmental degradation that is causing the current mass extinction began to accelerate in 1950, we are left with the precise placement of the “golden spike,” and the d14C is a good candidate.

Summary and Conclusions

Life on planet Earth has enjoyed times of great fecundity extending for millions of years that were punctuated by relatively brief catastrophic events that closed the door on the old forms and opened up new pathways for life to evolve. For most of geologic time, these extinction events are very poorly understood, as the main types of life were relatively simple bacteria that left a poor fossil record. More complex life forms that were capable of secreting hard parts that left a good fossil record emerged about 542 million years ago at the beginning of the Cambrian. Since that time, there have been five catastrophic intervals during which most of the kinds of life were eliminated forever. These were the end of the Ordovician (about 445 million years ago), the near-end Devonian (about 372 million years ago), the end-Permian (about 252 million years ago), the end-Triassic (about 201 million years ago) and the end-Cretaceous event (about 65 million years ago). The end-Permian event was the worst—until now.

The end-Permian extinction event has strong parallels to the current human-caused mass extinction. The triggering event for the end-Permian event was the eruption of great quantities of magma in Siberia and the burning of the vast coal fields in the region that loaded the atmosphere with CO2 and other greenhouse gases, dramatically warmed the planet, shut down oceanic circulation, poisoned the atmosphere and ocean, and lead to the collapse of life on the planet. It took millions of years to recover from this event. Today, humans are burning those same fossil fuels, loading the environment with greenhouse gases, cutting down forests, and poisoning the oceans and freshwater, which not only degrades our planet but attenuates her ability to renew herself. Our effects will last millions of years, and in fact forever in the case of the hundreds of thousands of species that have already become extinct directly because of human activity. At this point, the best we can hope for is to minimize the damage by turning to a sustainable lifestyle. We make choices every day that can help or hinder our effects, including our diet, transportation, and the manufactured products we purchase.

Choose wisely.

v1n1-puckett-photo

Dr. Mark Puckett in Cuba, December, 2010

End Notes

  1. ^Almost all elements have two types of particles in their nucleus: protons and neutrons. The exception is the protium form of hydrogen, which only has a proton.  The neutrons act to hold the nucleus together as it wobbles and vibrates, but too many or too few neutrons make a nucleus unstable, which results in radioactive decay. All carbon has 6 protons, but can have different numbers of neutrons, which determine its different isotopes. The number of protons plus the number of neutrons is the atomic mass number. There are two stable forms of carbon that presumably were formed billions of years ago by some star during nuclear fusion, carbon-12 and carbon-13. Other forms of carbon, such as carbon-14, are radioactive and must be continually created in the atmosphere.
  2. ^Two of the stable isotopes of oxygen that are very useful as a thermometer of ancient temperatures are oxygen-16 and oxygen-18. This ratio has long been known to be directly related to temperature, with an increase in the amount of oxygen-18 indicating cooler conditions during the formation of rocks and fossils. Many studies have used this information to infer the past conditions on the surface of the planet, particularly during times of mass extinctions.
  3. ^A. Vieth and H. Wilkes, “Stable Isotopes in Understanding Origin and Degradation Processes of Petroleum,” in Handbook of Hydrocarbon and Lipid Microbiology, ed. K.N. Timmis (Berlin: Springer-Verlag, 2010), 97–111.
  4. ^J.J. Sepkoski, “A Factor Analytic Description of the Phanerozoic Marine Record,” Paleobiology 7, no. 1 (1981): 36–53.
  5. ^“Colorado Plateau Geosystems,” Colorado Plateau Geosystems, Last modified May 2015, http://cpgeosystems.com/index.html.
  6. ^D. Erwin, Extinction: How Life on Earth Nearly Ended 250 Million Years Ago (Princeton: Princeton University Press, 2006), 320.
  7. ^J.O. Kaplan et al., “Holocene Carbon Emissions as a Result of Anthropogenic Land Cover Change,” Holocene 21, no. 5 (2010): 775–791.
  8. ^F.M. Gradstein et al., 2012, The Geologic Time Scale (Amsterdam, Elsevier, 2012): 1176.
  9. ^S.M. Stanley and J.A. Luczaj, Earth System History, 4th ed., (New York: W.H. Freeman, 2014) 608.
  10. ^W.B.N. Berry, R.L. Ripperdam, and S.C. Finney, “Late Ordovician Extinction: A Laurentian View,” Geological Society of America Special Paper 356 (2002) 463–471.
  11. ^M.M. Joachimski and W. Buggisch, “Conodont Apatite δ18Signatures Indicate Climatic Cooling as a Trigger of the Late Devonian Mass Extinction,” Geology 30, no. 8 (2002): 711–714.
  12. ^R.J. Twitchett et al., “Rapid and Synchronous Collapse of Marine and Terrestrial Ecosystems During the End-Permian Biotic Crisis,” Geology 29, no. 4 (2001): 351–354.
  13. ^J.L. Payne et al., “Large Perturbations of the Carbon Cycle During the Recovery from the End-Permian Extinction,” Science 305 (2004): 506–509.
  14. ^P. Gorjan, K. Kaiho, and Z.Q. Chen, “A Carbon-isotope Study of an End-Permian Mass-Extinction Horizon, Bulla, Northern Italy: A Negative d13C Shift Prior to the Marine Extinction,” Terra Nova 20 (2008): 253–258.
  15. ^G. Luo et al., “Stepwise and Large-Magnitude Negative Shift in d13Ccarb Preceded the Main Marine Mass Extinction of the Permian-Triassic Crisis Interva,” Palaeogeography, Palaeoclimatology, Palaeoecology 299 (2011): 70–82.
  16. ^S.Z. Shen et al., “Calibrating the End-Permian Mass Extinction,” Science 334 (2011): 1367–1372.
  17. ^Chu, J., “Siberian Traps Likely Culprit for End-Permian Extinction,” MIT News on Campus and Around the World, Last modified November 24, 2015, http://www.dailygalaxy.com/my_weblog/2013/11/the-great-dying-new-insights-into-the-most-severe-mass-extinction-in-earths-history.html.
  18. ^S.Z. Shen et al., “Calibrating the End-Permian Mass Extinction,” Science 334 (2011): 1367–1372.
  19. ^M.M. Joachimski et al., “Climate Warming in the Latest Permian and the Permian-Triassic Mass Extinction,” Geology 40, no. 3 (2012): 195–198.
  20. ^L.R. Kump, A. Pavlov, and M.A. Arthur, “Massive Release of Hydrogen Sulfide to the Surface Ocean and Atmosphere During Intervals of Oceanic Anoxia,” Geology 33, no. 5 (2005): 397–400.
  21. ^P. Ward, Gorgon: Paleontology, Obsession, and the Greatest Catastrophe in Earth’s History (New York, Viking Press, 2005), 288.
  22. ^K.M. Meyer, “d13C Evidence that High Primary Productivity Delayed Recovery from End-Permian Mass Extinction,” Earth and Planetary Science Letters 302, no. 3-4 (2011): 378–384.
  23. ^S.E. Grasby, H. Sanei, and B. Beauchamp, “Catastrophic Dispersion of Coal Fly Ash into the Oceans During the Latest Permian Extinction,” Nature Geoscience 4 (2011): 104–107.
  24. ^S.P. Hesselbo et al., “Terrestrial and Marine Extinction at the Triassic-Jurassic Boundary Synchronized with Major Carbon-cycle Perturbation: A Link to Initiation of Massive Volcanism?” Geology 30, no. 3 (2002): 251–254.
  25. ^S.L. Lewis and M.A. Maslin, “Defining the Anthropocene,” Nature 519 (2015): 171–180.
  26. ^Michael McGee, “CO2-Earth,” ProOxygen, last modified 2016, https://www.co2.earth.
  27. ^A. Ganopolski, R. Winkelmann, and H.J. Schellnhuber, “Critical Insolation-CO2 Relation for Diagnosing Past and Future Glacial Inception,” Nature 529 (2016): 200–205.
  28. ^WWF, “How Many Species Are We Losing?” World Wide Fund for Nature, last modified 2016, http://wwf.panda.org/about_our_earth/biodiversity/biodiversity/
  29. ^A.W. Crosby, “Columbian Exchange: Plants, Animals, and Disease between Old and New World,” The Encyclopedia of Earth, 2009, last modified May 5, 2015, http://www.eoearth.org/view/article/151313/.
  30. ^C. MacFarling Meure et al. “Law Dome CO2, CH4 and N2 Ice Core Records Extended to 2000 years BP,” Geophysical Research Letters 33, no. 14 (2006).
  31. ^R. Eveleth, “Nuclear bombs made it possible to carbon date human tissue,” SmartNews, 2013, Last modified February 19, 2013, http://www.smithsonianmag.com/smart-news/nuclear-bombs-made-it-possible-to-carbon-date-human-tissue-20074710/?no-ist.

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