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Studying for midterms, please help me with this homework, thanks.

Studying for midterms, please help me with this homework, thanks.

56 Scientific American, July 2011 © 2011 Scientific American Last








C L I M AT E C H A N G E THE Surprising new evidence suggests the pace of the earth?s most abrupt


prehistoric warm-up paled in comparison to what we face today.


The episode has lessons for our future


By Lee R. Kump


July 2011, 57 Illustration by Ron Miller © 2011 Scientific American P Lee R. Kump is a professor of geosciences at Pennsylvania State


University and co-author of the book Dire Predictions: Understanding


Global Warming (DK Adult, 2008). Planetary fevers are his specialty. OLAR BEARS DRAW MOST VISITORS TO


Spitsbergen, the largest island in


Norway?s Svalbard archipelago. For


me, rocks were the allure. My colleagues and I, all geologists and climate scientists, flew to this remote


Arctic island in the summer of 2007


to find definitive evidence of what was then considered the


most abrupt global warming episode of all time. Getting to the


rocky outcrops that might entomb these clues meant a rugged,


two-hour hike from our old bunkhouse in the former coalmining village of Longyearbyen, so we set out early after a


night?s rest. As we trudged over slippery pockets of snow and


stunted plants, I imagined a time when palm trees, ferns and


alligators probably inhabited this area.


Back then, around 56 million years ago, I would have been


drenched with sweat rather than fighting off a chill. Research


had indicated that in the course of a few thousand years?a mere


instant in geologic time?global temperatures rose five degrees


Celsius, marking a planetary fever known to scientists as the


Paleocene-Eocene Thermal Maximum, or PETM. Climate zones


shifted toward the poles, on land and at sea, forcing plants and


animals to migrate, adapt or die. Some of the deepest realms of


the ocean became acidified and oxygen-starved, killing off many


of the organisms living there. It took nearly 200,000 years for the


earth?s natural buffers to bring the fever down.


The PETM bears some striking resemblances to the humancaused climate change unfolding today. Most notably, the culprit


behind it was a massive injection of heat-trapping greenhouse


gases into the atmosphere and oceans, comparable in volume to


what our persistent burning of fossil fuels could deliver in coming centuries. Knowledge of exactly what went on during the


PETM could help us foresee what our future will be like. Until recently, though, open questions about the event have made predictions speculative at best. New answers provide sobering clarity. They suggest the consequences of the planet?s last great global warming paled in comparison to what lies


ahead, and they add new support for predictions that humanity will suffer if our


course remains unaltered.


GREENHOUSE CONSPIRACY TODAY INVESTIGATORS think the PETM unfolded something like this: As is true of


our current climate crisis, the PETM began, in a sense, with the burning of fossil


fuels. At the time the supercontinent Pangaea was in the final stages of breaking


up, and the earth?s crust was ripping apart, forming the northeastern Atlantic Ocean. As a result, huge volumes of molten rock


and intense heat rose up through the landmass that encompassed Europe and Greenland, baking carbon-rich sediments


and perhaps even some coal and oil near the surface. The baking


sediments, in turn, released large doses of two strong greenhouse


gases, carbon dioxide and methane. Judging by the enormous


volume of the eruptions, the volcanoes probably accounted for


an initial buildup of greenhouse gases on the order of a few hundred petagrams of carbon, enough to raise global temperature by


a couple of degrees. But most analyses, including ours, suggest it


took something more to propel the PETM to its hottest point.


A second, more intense warming phase began when the volcano-induced heat set other types of gas release into motion.


Natural stirring of the oceans ferried warmth to the cold seabed,


where it apparently destabilized vast stores of frozen methane


hydrate deposits buried within. As the hydrates thawed, methane gas bubbled up to the surface, adding more carbon into the


atmosphere. Methane in the atmosphere traps heat much more


effectively than CO2 does, but it converts quickly to CO2. Still, as


long as the methane release continued, elevated concentrations IN BRIEF Global temperature rose - That intense gas release The speed of today?s rise - 58 Scientific American, July 2011 © 2011 Scientific American PETM curve)


modern curve




CLIMATIC CHANGE, of that gas would have persisted, strongly amplifying the greenhouse effect and the resulting temperature rise.


A cascade of other positive feedbacks probably ensued at the


same time as the peak of the hydrate-induced warming, releasing yet more carbon from reservoirs on land. The drying, baking


or burning of any material that is (or once was) living emits


greenhouse gases. Droughts that would have resulted in many


parts of the planet, including the western U.S. and western Europe, most likely exposed forests and peat lands to desiccation


and, in some cases, widespread wildfires, releasing even more


CO2 to the atmosphere. Fires smoldering in peat and coal seams,


which have been known to last for centuries in modern times,


could have kept the discharge going strong.


Thawing permafrost in polar regions probably exacerbated


the situation as well. Permanently frozen ground that locks


away dead plants for millions of years, permafrost is like frozen


hamburger in the freezer. Put that meat on the kitchen counter,


and it rots. Likewise, when permafrost defrosts, microbes consume the thawing remains, burping up lots of methane. Scientists worry that methane belches from the thawing Arctic could


greatly augment today?s fossil-fuel-induced warming. The potential contribution of thawing permafrost during the PETM


was even more dramatic. The planet was warmer then, so even


before the PETM, Antarctica lacked the ice sheets that cover the


frozen land today. But that continent would still have had permafrost?all essentially ?left on the counter? to thaw.


When the gas releases began, the oceans absorbed much of


the CO2 (and the methane later converted to CO2). This natural


carbon sequestration helped to offset warming at first. Eventually, though, so much of the gas seeped into the deep ocean that it


created a surplus of carbonic acid, a process known as acidification. Moreover, as the deep sea warmed, its oxygen content dwindled (warmer water cannot hold as much of this life-sustaining


gas as cold water can). These changes spelled disaster for certain


microscopic organisms called foraminifera, which lived on the


seafloor and within its sediments. The fossil record reveals their


inability to cope: 30 to 50 percent of those species went extinct.




has been clear since 1990, when a pair of California-based re- searchers first identified the event in a multimillion-year climate


record from a sediment core drilled out of the seabed near Antarctica. Less apparent were the details, including exactly how


much gas was released, which gas predominated, how long the


spewing lasted and what prompted it.


In the years following that discovery, myriad scientists analyzed hundreds of other deep-sea sediment cores to look for answers. As sediments are laid down slowly, layer by layer, they trap


minerals?including the skeletal remains of sea life?that retain


signatures of the composition of the surrounding oceans or atmosphere as well as life-forms present at the time of deposition. The


mix of different forms, or isotopes, of oxygen atoms in the skeletal


remains revealed the temperature of the water, for instance.


When well preserved, such cores offer a beautiful record of climate history. But many of those that included the PETM were not


in good shape. Parts were missing, and those left behind had been


degraded by the passage of time. Seafloor sediment is typically


rich in the mineral calcium carbonate, the same chemical compound in antacid tablets. During the PETM, ocean acidification


dissolved away much of the carbonate in the sediments in exactly


the layers where the most extreme conditions of the PETM era


should have been represented.


It is for this reason that my colleagues and I met up in Spitsbergen in 2007 with a group of researchers from England, Norway and the Netherlands, under the auspices of the Worldwide


Universities Network. We had reason to believe that rocks from


this part of the Arctic, composed almost entirely of mud and clay,


could provide a more complete record?and finally resolve some


of the unanswered questions about that ancient warming event.


Actually we intended to pluck our samples from an eroded plateau, not from underneath the sea. The sediments we sought


were settled into an ancient ocean basin, and tectonic forces at


play since the PETM had thrust that region up above sea level,


where ice age glaciers later sculpted it into Spitsbergen?s spectacular range of steep mountains and wide valleys.


After that first scouting trip from Longyearbyen, while devising plans for fieldwork and rock sampling, we made a discovery


that saved much heavy lifting. We learned from a forward-thinking local geologist that a Norwegian mining company he worked


for had cored through sediment layers covering the PETM era


years earlier. He had taken it on himself to preserve kilometers Now and Then


How fast the world warms depends on


how fast greenhouse gases build in the


atmosphere. Projections anticipate a


warm-up of about eight degrees Celsius


by 2400 if fossil-fuel burning and carbon


sequestration go unaltered. The projected


carbon release, about 5,000 petagrams,


is similar in volume to what fueled the


Paleocene-Eocene Thermal Maximum,


or PETM, but the past rate, once thought


to be rapid, was slower than today?s. Global temperature is rising much more quickly today than it did during the PETM


Modern: Fueled by high emission rates


(up to 25 petagrams of carbon a year),


global temperature is rising quickly and 8 Temperature Rise


(degrees Celsius) 2 SURPRISING FINDING PETM: Slow but steady emissions


(up to 1.7 petagrams of carbon a year)


resulted in a more gradual heating of


the planet some 56 million years ago 4 Where we


are today




Greenhouse gas release begins 10,000


Duration (years) 20,000 July 2011, 59 Graphic by Jen Christiansen © 2011 Scientific American STRETCHING TIME OUR ARCTIC CORES turned out to be quite special. The first to record the full duration of the PETM warm-up and recovery, they


provided a much more complete snapshot of the period when


greenhouse gases were being released to the atmosphere. We


suspected that the unprecedented fidelity of these climate records would ultimately provide the most definitive answers to


date about the amount, source and duration of gas release. But


to get those results, we had to go beyond extrapolations from


the composition and concentration of materials in the cores.


We asked Ying Cui, my graduate student at Pennsylvania State


University, to run a sophisticated computer model that simulated the warming based on what we knew about the changes in


the carbon isotope signatures from the Arctic cores and the degree of dissolution of seafloor carbonate from deep-sea cores.


Cui tried different scenarios, each one taking a month of computer time to play out the full PETM story. Some assumed greater


contributions from methane hydrates, for instance; others assumed more from CO2 sources. The scenario that best fit the physical evidence required the addition of between 3,000 and 10,000


petagrams of carbon into the atmosphere and ocean, more than


the volcanoes or methane hydrates could provide; permafrost or


peat and coal must have been involved. This estimate falls on the


high side of those made previously based on isotope signatures


from other cores and computer models. But what surprised us


most was that this gas release was spread out over approximately


20,000 years?a time span between twice and 20 times as long as


anyone has projected previously. That lengthy duration implies


that the rate of injection during the PETM was less than two petagrams a year?a mere fraction of the rate at which the burning of


fossil fuels is delivering greenhouse gases into the air today. Indeed, CO2 concentrations are rising probably 10 times faster now


than they did during the PETM.


This new realization has profound implications for the future. The fossil record tells us that the speed of climate change


has more impact on how life-forms and ecosystems fare than


does the extent of the change. Just as you would prefer a hug


from a friend to a punch in the stomach, life responds more favorably to slow changes than to abrupt ones. Such was the case


during an extreme shift to a hothouse climate during the Cretaceous period (which ended 65 million years ago, when an asteroid impact killed the dinosaurs). The total magnitude of green- I M P L I C AT I O N S Mild Planetary fevers that come on suddenly?


such as the scenario unfolding today?are


much harder on life than the slower ones are.


The fossil record shows that the slow shift to


a hothouse from 120 million to 90 million


years ago, during the Cretaceous period, was


innocuous relative to the PETM, which was


1,000 times more abrupt. The latter episode


has long been analyzed for clues to how our


own warming trend will play out, but today?s


much faster temperature change suggests


that the consequences for life on earth will be


harsher than anything that has come before. Moderate Severe Lessons from


Past Warmings


Harm to Life of that core on the off chance that scientists would one day find


them useful. He led us to a large metal shed on the outskirts of


town where the core is now housed, since cut into 1.5-meter-long


cylinders stored in hundreds of flat wood boxes. Our efforts for


the rest of that trip, and during a second visit in 2008, were directed at obtaining samples from selected parts of that long core.


Back in the lab, over several years, we extracted from those


samples the specific chemical signatures that could tell us about


the state of the earth as it passed into and out of the PETM. To understand more about the greenhouse gas content of the air, we


studied the changing mix of carbon isotopes, which we gleaned


mostly from traces of organic matter preserved in the clay. By


making extractions and analyses for more than 200 layers of the


core, we could piece together how these factors changed over


time. As we suspected, the isotope signature of carbon shifted dramatically in the layers we knew to be about 56 million years old. 146 Millions of Years Ago (mya) C R E T house warming during the Cretaceous was similar to that of the


PETM, but that former episode unfolded over millions, rather


than thousands, of years. No notable extinctions occurred; the


planet and its inhabitants had plenty of time to adjust.


For years scientists considered the PETM to be the supreme


example of the opposite extreme: the fastest climate shift ever


known, rivaling the gloomiest projections for the future. In that


light, the PETM?s outcomes did not seem so bad. Aside from the


unlucky foraminifera in the deep sea, all animals and plants apparently survived the heat wave?even if they had to make some


serious adaptations to do so. Some organisms shrank. In particular, mammals of the PETM are smaller than both their predecessors and descendants. They evolved this way presumably because smaller bodies are better at dissipating heat than larger


ones. Burrowing insects and worms, too, dwarfed.


A great poleward migration saved other creatures. Some even


thrived in their expanded territories. At sea, the dinoflagellate


Apectodinium, usually a denizen of the subtropics, spread to the


Arctic Ocean. On land, many animals that had been confined to


the tropics made their way into North America and Europe for the


first time, including turtles and hoofed mammals. In the case of


mammals, this expansion opened up myriad opportunities to


evolve and fill new niches, with profound implications for human


beings: this grand diversification included the origin of primates.


TOO FAST? NOW THAT WE KNOW the pace of the PETM was moderate at worst


and not really so fast, those who have invoked its rather innocuous biological consequences to justify impenitence about fossil-fuel combustion need to think again. By comparison, the 60 Scientific American, July 2011 © 2011 Scientific American A Cretaceous Hothouse (Slow) PETM (Moderately fast) degree Celsius Rate of heating: Rate of heating: Main underlying cause: Volcanic eruptions


Environmental change: Oceans absorbed


carbon dioxide slowly so did not acidify


Life?s response: Nearly all creatures had time


to adapt or migrate C E O U S Modern Warming (Fast)


Rate of heating: 1 to 4 ° Duration: Thousands of years


Overall warming: 5 °C


Main underlying cause: Volcanoes; methane


bubbling up from the ocean bottom; peat and Duration: Millions of years


Overall warming: 5 °C 65 mya ° Environmental change:


Life?s response:


but most life on land adapted or migrated Duration: Decades to hundreds of years


Overall warming:




Main underlying cause: Fossil-fuel burning


Environmental change: Acidifying oceans; more


extreme weather, glacier melting; sea-level rise


Life?s response: Poleward movement of many


species; habitat loss; coral bleaching; extinctions 56 mya PALEOCENE E O C E N E climate shift currently under way is happening at breakneck


speed. In a matter of decades, deforestation and the cars and


coal-fired power plants of the industrial revolution have increased CO2 by more than 30 percent, and we are now pumping


nine petagrams of carbon into the atmosphere every year. Projections that account for population growth and increased industrialization of developing nations indicate that rate may


reach 25 petagrams a year before all fossil-fuel reserves are




Scientists and policy makers grappling with the potential effects of climate change usually focus on end products: How


much ice will melt? How high will sea level rise? The new lesson


from PETM research is that they should also ask: How fast will


these changes occur? And will the earth?s inhabitants have time


to adjust? If change occurs too fast or if barriers to migration or


adaptation loom large, life loses: animals and plants go extinct,


and the complexion of the world is changed for millennia.


Because we are in the early interval of the current planetary


fever, it is difficult to predict what lies ahead. But already we


know a few things. As summarized in recent reports from the


Intergovernmental Panel on Climate Change, ecosystems have


been responding sensitively to the warming. There is clear evidence of surface-water acidification and resulting stress on sea


life [see ?Threatening Ocean Life from the Inside Out,? by Marah


J. Hardt and Carl Safina; SCIENTIFIC AMERICAN, August 2010].


Species extinctions are on the rise, and shifting climate zones


have already put surviving plants and animals on the move, often with the disease-bearing pests and other invasive species


winning out in their new territories. Unlike those of the PETM,


modern plants and animals now have roads, railways, dams, cit- Today ies and towns blocking their migratory paths to more suitable


climate. These days most large animals are already penned into


tiny areas by surrounding habitat loss; their chances of moving


to new latitudes to survive will in many cases be nil.


Furthermore, glaciers and ice sheets are melting and driving


sea-level rise; coral reefs are increasingly subject to disease and


heat stress; and episodes of drought and flooding are becoming


more common. Indeed, shifts in rainfall patterns and rising


shorelines as polar ice melts may contribute to mass human migrations on a scale never before seen. Some have already begun


[see ?Casualties of Climate Change,? by Alex de Sherbinin, Koko


Warner and Charles Ehrhart; SCIENTIFIC AMERICAN, January].


Current global warming is on a path to vastly exceed the


PETM, but it may not be too late to avoid the calamity that


awaits us. To do so requires immediate action by all the nations


of the world to reduce the buildup of atmospheric carbon dioxide?and to ensure that the Paleocene-Eocene Thermal Maximum remains the last great global warming. The Paleocene-Eocene Thermal Maximum: A Perturbation of Carbon Cycle, Climate,


and Biosphere with Implications for the Future.


Annual Review of Earth and Planetary Sciences,


America?s Climate Choices.


Slow Release of Fossil Carbon during the Palaeocene-Eocene Thermal Maximum.


Nature Geoscience


SCIENTIFIC AMERICAN ONLINE July 2011, 61 Illustrations by Ron Miller, Graphic by Emily Cooper © 2011 Scientific American


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