Countdown to catastrophe

Total human carbon dioxide emissions could match those of Earth’s last major greenhouse warming event in fewer than five generations, according to a new University of Michigan study.

The research finds humans are pumping carbon dioxide into the atmosphere at a rate nine to 10 times higher than the greenhouse gas was emitted during the Paleocene-Eocene Thermal Maximum, or PETM, a global warming event that occurred roughly 56 million years ago.

The results suggest if carbon emissions continue to rise, the total amount of carbon dioxide injected into the atmosphere since humans started burning fossil fuels could equal the amount released during the PETM as soon as 2159.

“You and I won’t be here in 2159, but that’s only about four generations away,” says Philip Gingerich, U-M paleoclimate researcher and author of the study, published Jan. 30 in Paleoceanography and Paleoclimatology, a journal of the American Geophysical Union.

“When you start to think about your children and your grandchildren, and your great-grandchildren, you’re about there,” says Gingerich, a professor emeritus of earth sciences, evolutionary biology and anthropology and a curator emeritus of vertebrate paleontology at the U-M Museum of Paleontology.

Scientists often use the PETM as a benchmark against which to compare modern climate change. But the U-M study shows we’re on track to meet this benchmark much sooner than previously thought, as the pace of today’s warming far outstrips any climate event that has happened since the extinction of the dinosaurs.

“Given a business-as-usual assumption for the future, the rates of carbon release that are happening today are really unprecedented, even in the context of an event like the PETM,” says Gabriel Bowen, a geophysicist at the University of Utah who was not connected to the new study. “We don’t have much in the way of geologic examples to draw from in understanding how the world responds to that kind of perturbation.”The exact environmental consequences of PETM-like carbon levels are unclear, but the increased temperatures will likely drive many species to extinction with the lucky ones being able to adapt or migrate, according to Larisa DeSantis, a paleontologist at Vanderbilt University who was not connected to the new study. In addition, it will take thousands of years for the climate system cool down, she says.

“It’s not just about 100 years from now; it’s going to take significant periods of time for that carbon dioxide to make its way back into the Earth’s crust,” DeSantis says. “It’s not a short-term event. We’re really committing ourselves to many thousands of years of a warmer world if we don’t take action quickly.”

The PETM was a global warming event that occurred roughly 56 million years ago. Scientists are unsure what caused it, but during the event massive quantities of carbon dioxide were released into Earth’s atmosphere, rapidly spiking global temperatures by 5 to 8 degrees Celsius (9 to 14 degrees Fahrenheit). Average global temperatures during the PETM peaked at about 23 degrees Celsius (73 degrees Fahrenheit), about 7 degrees Celsius (13 degrees Fahrenheit) higher than today’s average.

Scientists think that during this time and the warm period that followed, the poles were ice-free and the Arctic was home to palm trees and crocodiles. It’s not the hottest Earth has ever been, but the PETM was the warmest period since the extinction of the dinosaurs 66 million years ago.

Scientists can’t pin down exactly how much carbon was injected into the atmosphere during the PETM or exactly how long the event lasted. But their best estimates say between 3,000 and 7,000 gigatons of carbon accumulated over a period of 3,000 to 20,000 years, based on ocean sediment cores that show changes to carbonate minerals laid down during this time.

The massive carbon release and temperature spike drastically altered Earth’s climate, causing a major extinction of organisms in the deep ocean that are a key link in the marine food web. Land animals got smaller and migrated north to cooler climates. Some groups of modern mammals, including primates, appeared for the first time soon after the PETM, but scientists are unsure whether this happened as a direct result of the rapid environmental change.

Climate scientists use the PETM as a case study for understanding what environmental changes might happen under current human-caused climate change and when those changes might take effect. But they can only average carbon emissions during the PETM over the whole duration of the event—thousands of years. They don’t know what those emissions rates were like on a yearly basis, so it’s difficult to compare them to the pace of carbon emissions today.

In the new study, Gingerich found a way to mathematically compare modern carbon emissions to PETM emissions on the same time scale. The results showed current carbon emission rates are nine to 10 times higher than those during the PETM.

“To me, it really brought home how rapidly and how great the consequences are of the carbon we’re producing as a people,” Gingerich says.

Projecting current emissions into the future, Gingerich found that if emissions continue to rise, we could be facing another PETM-like event in fewer than five generations. The total carbon accumulated in the atmosphere could hit the lowest estimate of carbon accumulated during the PETM—3,000 gigatons—in the year 2159. It would hit the maximum estimated emissions—7,126 gigatons—in 2278, based on Gingerich’s calculations. Humans have emitted roughly 1,500 gigatons of carbon as of 2016.

“The fact that we could reach warming equivalent to the PETM very quickly, within the next few hundred years, is terrifying,” DeSantis says.

The findings suggest scientists may not be able to predict the environmental or biological changes that will happen in the coming years based on what happened during the PETM because today’s warming is occurring so much faster, according to DeSantis. What makes predictions harder is that today’s climate starts from a cooler baseline than the PETM and the species that inhabit Earth are different than those of 56 million years ago.

“It’s hard to compare biotic effects because the world during the PETM was quite different,” DeSantis says. “We live in a very different world today, with different groups of animals, with humans being the dominant species … but we know there are many negative consequences of dramatic warming on vast numbers of species, including our own.”

This news release was provided by the American Geophysical Union.


  1. Allan Tweddle - 1961

    As an industrial engineering graduate in 1961, in my return to my native Canada, I was Immediately immersed in the subject of air quality, especially in manufacturing.

    Ever since I have faced solving air quality problems in everything from steel mills to surgeries.

    When my company transferred me to California, I subsequently became involved as a consultant to the South Coast Air Quality Management District and the California Air Resources Board. And in several projects, we were able to “push the envelope” and achieve zero emissions in industries that were quite the polluters.

    Ever since NASA’s Dr. James Hansen‘s testimony to Congress, I’ve been a student of, and a vociferous advocate of, addressing climate change as not only an imperative, but a job creating opportunity.

    I’m very pleased to see that study completed in Ann Arbor, and will use it as a reference in my continuing efforts to educate people about the critical nature of climate change and the very real economic opportunities that it is demonstrating are technically and financially possible.

    I now live in Charleston West Virginia, which in my talks are referred to as “the Epicenter of Climate Denial ” because the state is dominated by the coal industry and the majority of legislators under the thumb of the “Friends of Coal” organization.

    Finally, I have invested my entire life savings, and along with two other engineers and 14 friends and family investors, developed an innovative and disruptive approach to an onboard system to the worlds airlines that will reduce the carbon footprint of every plane that is converted to our system.

    We are currently challenge to find anyone interested in investments in the manufacturing of aircraft systems, so would appreciate any guidance or advice or introductions That you might be able to offer.

    Thank you for this focus on climate change by my alma mater



  2. Mike Jefferson - 1980

    There are several interesting points to consider. First, the amount of CO2 being pumped into the atmosphere as the result of human activities is increasing. No one disputes that. The questions which remain include whether the emissions are problematic and if so how can they be controlled? Taxing Americans is not the answer. The increases in CO2 emissions are largely the result of population increases and practices of burning and deforestation in the developing world. We need to actively advocate for population control in those nations and consider moving to non carbon generating power sources. Libbies won’t like the solutions as it won’t involve stylish Teslas or pretty bird slaughtering and climate altering windmills in other peoples’ backyards. Instead, adopting nuclear energy generation (thorium is lower risk and easily achievable) is our best bet.


  3. Bruce Nourse - 1964 - Sci Eng

    Another article on global warming. At least this one points out that it is
    being driven by human beings. But what about the rapid loss of living
    species? And trashing of the land and ocean? And vast collections of plastic on land
    and in the ocean? Rapid deforestation to make land for growing food?
    etc. etc. This list is almost endless.

    I believe that if we were somehow able to completely clean the atmosphere
    and arrest global warming that the other effects of human overpopulation
    will still drive us to extinction in less than 200 years. There is ONLY one
    solution to the destruction of the living environment — a very rapid reduction in
    human population.

    I don’t think we, as a population, can organize well enough to avert the
    catastrophe mentioned in your article. It would take a wonderful, but
    selective, natural disaster to reduce the population to an acceptable level. But
    even if we don’t know a solution to the problem, we should be talking about it.
    Another article about global warming gives people the hope and expectation
    that if they just join this effort that all will be saved. Just not true.

    Please print articles with scientific estimates of human population vs
    expected human extinction. Driving people to reduce global warming alone is
    misleading and a waste of time.

    We need more articles that illuminate the whole problem on an inclusive basis.

    My two cents.


  4. Paul Katona - 1971

    We need to manage our carbon, not only to restore our climate, but to restore Mother Earth, our biosphere, which provides the air we breathe, the water we drink, and the food we eat. Yes, it will be expensive and difficult socially and politically. The good news is that if we are clever in our approach we could wind up with a more stable, manageable climate, a more efficient economy, and a healthier agricultural system and biosphere.

    We eventually learned that we had to quit throwing our carbon, our night soil and garbage into the street in Medieval Europe. Now we’ve learned that the carbon that industrialized society has extracted as coal and oil then dumped as carbon dioxide (CO2) into the atmosphere will most certainly have dire social and great economic costs, now and into the future.

    People and institutions resist change. Europe lost one third of its population due to plague before sanitation and hygiene were employed and the disease abated. But there it is. When faced with dire circumstances and catastrophe we manage to change our ways. Hopefully we can hear the alarms and see the warning signs and begin moving Mother Earth toward the habitat that will let humanity and the biosphere flourish.

    Today due to energy intensive modern farming practices of plowing and chemistry we have lost carbon in our soil where it is needed to provide fertility, water retention and tilth. We are losing farmland and our farmers are going broke. Our future food security is at risk.
    We don’t want carbon in the air but we do want it in the ground.

    So a change we can make that can connect these two is our approach to agriculture. Plants and microbes naturally want to take carbon out of the air and put it into the soil. It could be an important part of a solution to our carbon problem as well as food security and the health of the farming business. Yes, we need to get better at limiting the fossil energy we use. Yet agriculture is the best opportunity we have to pull carbon dioxide out of the air and lock it into the ground, maybe a lot of it.

    Growing food with Regenerative Agriculture builds soil carbon content and soil biology to supply a large part of the nutrition that plants need. Carbon Farming is where the farmer/landowner gets paid for the carbon his farms biology pulls from the air and locks into the soil long term. Careful management such as crop rotation of multi specie cover crops, and “mob” grazing let’s the soil biology build soil naturally. Expensive plowing and applied chemicals are kept to a bare minimum as these release carbon. They also destroy soil biology, its tilth, and water holding ability. Estimates vary but soil scientists Ray Archuleta and Eric Toensmeier, have calculated that an increase in Soil Organic Content (SOC) of 1% to 2% across the worlds agricultural land would sequester all the atmospheric carbon man has released since the Industrial Revolution.

    This would be a huge turn around. Depending on how you count, agriculture accounts for 30% or more of the man made atmospheric CO2. Fossil fuels are burned for the extensive use of farm equipment and food transportation. Vast amounts of energy are used to make chemical fertilizers. Carbon that has been sequestered in the, trees and flora are released during slash and burn clearing. Plowing releases sequestered carbon into the atmosphere as CO2. This is because the soil is exposed to the air. It can also compact and ruin the soils water holding ability. Through plowing and farming the prairie we have lost more than half the carbon locked in the soil into the air. As the fertility of the soil goes down the cost of producing food goes up. As the soil further degrades food security could be an issue. This is especially true if our climate degrades.

    Our best science tells us that we are creating a heat trap, a greenhouse, with a thickening blanket of CO2 in the atmosphere. The added energy drives our weather to extremes and away from normal patterns. This will make living and growing food expensive and difficult The higher concentrations of CO2 in the atmosphere are absorbed into the ocean turning them acidic, altering marine biology. Climate and ecological systems are complicated with many things that can affect them. It is clear that climate and our eco system are changing. It is our obligation to push that change in a direction that is advantageous to us and our future generations.

    We must strategically manage our carbon It is time for this nation to implement a policy that encourages reduced carbon extraction and fossil fuel use, and the growth of alternative energy sources. Equally we need to pay farmers to sequester carbon long term into the soil through Carbon Farming practices as our best way to reduce atmospheric carbon.

    Some ideas have been put forward to facilitate this. They include a direct tax on carbon extraction similar to the Baker-Schultz proposal. The fee of about $40 per metric ton of carbon extracted or imported into this country would undoubtedly be passed on to the consumer. It would encourage conservation and alternative energy innovation. The fee collected by the government would then be used :
    1) Pay farmers/landowners for long term sequestration of Soil Organic Carbon on a per metric ton basis. Details to be established.
    2) Subsidize the lowest income brackets with an tax credit to offset their increased energy costs.
    3) Pay for research and education in Regenerative Farming, energy conservation and alternative energy innovation and application.

    It should be apparent that we must manage our carbon as a nation and ultimately as a species. We will have to change the way we do things, make investment to prevent the huge costs of weather extremes, and a dying Ecosystem.

    An idea that caught my attention was to promote CARBON FARMING as promoted by several pioneering researchers, farmers, and authors. This Regenerative type of agriculture pulls carbon dioxide out of the air and sequesters organic carbon long term in the soil. As a bonus the stored carbon returns natural fertility, tilth and water retention to the soil. There is, of course, debate as to how effective this could be. I would bet on the farmers. I don’t know of a more innovative. industrious group. I would bet that given the chance to make money sequestering carbon while growing food, lowering costs and building their soil; they would get very good at it. I have made a study of the topic and am in the process of making a video journal. You can find my project at FeedingMotherEarth.Info .

    Paul Katona


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