Science Current Events | Science News | Brightsurf.com
 

Studies of ancient climates suggest Earth is now on a fast track to global warming

February 17, 2006
Human activities are releasing greenhouse gases more than 30 times faster than the rate of emissions that triggered a period of extreme global warming in the Earth's past, according to an expert on ancient climates.

"The emissions that caused this past episode of global warming probably lasted 10,000 years. By burning fossil fuels, we are likely to emit the same amount over the next three centuries," said James Zachos, professor of Earth sciences at the University of California, Santa Cruz.

Zachos will present his findings this week at the annual meeting of the American Association for the Advancement of Science (AAAS) in St. Louis. He is a leading expert on the episode of global warming known as the Paleocene-Eocene Thermal Maximum (PETM), when global temperatures shot up by 5 degrees Celsius (9 degrees Fahrenheit). This abrupt shift in the Earth's climate took place 55 million years ago at the end of the Paleocene epoch as the result of a massive release of carbon into the atmosphere in the form of two greenhouse gases: methane and carbon dioxide.

Previous estimates put the amount of released carbon at 2 trillion tons, but Zachos showed that more than twice that amount-about 4.5 trillion tons-entered the atmosphere over a period of 10,000 years (Science, June 10, 2005). If present trends continue, this is the same amount of carbon that industries and automobiles will emit during the next 300 years, Zachos said.

Once the carbon is released into the atmosphere, it takes a long time for natural mechanisms, such as ocean absorption and rock weathering, to remove excess carbon from the air and store it in the soil and marine sediments. Weathering of land rocks removes carbon dioxide permanently from the air, but is a slow process requiring tens of thousands of years. The ocean absorbs carbon dioxide much more rapidly, but only to a point. The gas first dissolves in the thin surface layer of the ocean, but this surface layer quickly becomes saturated and its ability to absorb more carbon dioxide declines.

Only mixing with the deeper layers can help restore the ability of the surface water to absorb additional carbon dioxide from the atmosphere. But the natural processes that mix and circulate water between the ocean surface and deeper ocean layers work very slowly. A complete "mixing cycle" takes about 500 to 1,000 years, Zachos said.

The greenhouse emissions that triggered the PETM initially exceeded the ocean's absorption capacity, allowing carbon to accumulate in the atmosphere. Unfortunately, humans appear to be adding carbon dioxide to the air at a much faster rate: about the same amount of carbon (4.5 trillion tons), but within a few centuries instead of 10,000 years. What was emitted 55 million years ago over a period of about 20 ocean mixing cycles is now being emitted over a fraction of a cycle.

"The rate at which the ocean is absorbing carbon will soon decrease," Zachos said.

Compounding this concern is the possibility that higher temperatures could retard ocean mixing, further reducing the ocean's capacity to absorb carbon dioxide. This could have the kind of "positive feedback" effect that climate researchers worry about: reduced absorption, leaving more carbon dioxide in the air, causing more warming.

Higher ocean temperatures could also slowly release massive quantities of methane that now lie frozen in marine deposits. A greenhouse gas 20 times more potent than carbon dioxide, methane in the atmosphere would accelerate global warming even further.

Such positive feedback or "threshold" effects probably drove global warming during the PETM and a few other ancient climate extremes, Zachos said, and they could happen again. It is possible that we already are in the early stages of a similar climate shift, he said.

"Records of past climate change show that change starts slowly and then accelerates," he said. "The system crosses some kind of threshold."

Clues to what happened during the PETM lie buried deep inside the sediment at the bottom of the sea, which Zachos and his colleagues have probed during several cruises of the Ocean Drilling Program (ODP). Composed mainly of clay and the carbonate shells of microplankton, this sediment accumulates slowly, but steadily-up to 2 centimeters every millennium-and faithfully records changes in ocean chemistry. The layer of sediment deposited during the PETM, now buried hundreds of meters below the seafloor, tells a clear and compelling story of sudden change and slow recovery, he said.

During the PETM, unknown factors released vast quantities of methane that had been lying frozen in sediment deposits on the ocean floor. After release, most of the methane reacted with dissolved oxygen to form carbon dioxide, which made the seawater more acidic. Acidic seawater corrodes the carbonate shells of microplankton, dissolving them before they can reach the ocean floor and reducing the carbonate content of marine sediment.

Zachos led an international team of scientists that analyzed sediment cores recovered from several locations during an ODP cruise in the southeastern Atlantic. Collected at depths ranging from 2.5 to 4.8 kilometers (1.6 to 3.0 miles), each sediment core bore a telltale PETM imprint: a 10- to 30-centimeter layer of dark red carbonate-free clay sandwiched between bright white carbonate-rich layers.

By relating the thickness of the clay layer to the rate of accumulation of marine sediment, Zachos estimated that it took 100,000 years after the PETM for carbon dioxide levels in the air and water to return to normal. This finding is consistent with what geochemists have predicted using models of how the global carbon cycle will respond to carbon dioxide emissions from the burning of fossil fuels.

"We set out to test the hypotheses put forward by a small group of geochemists who model the global carbon cycle, and our findings support their predictions," Zachos said. "It will take tens of thousands of years before atmospheric carbon dioxide comes down to preindustrial levels. Even after humans stop burning fossil fuels, the effects will be long lasting."

University of California-Santa Cruz


Related Global Warming Current Events and Global Warming News Articles


Study shows global warming is unlikely to reduce winter deaths
A study by researchers at Columbia University's Mailman School of Public Health debunks the assumption that global warming will lead to a decline in the number of deaths in winter.

Climate change won't reduce winter deaths
In a study that contradicts the received wisdom on health impacts of climate change, scientists say that we shouldn't expect substantial reduction in winter deaths as a result of global warming.

Risk of major sea level rise in Northern Europe
Global warming leads to the ice sheets on land melting and flowing into the sea, which consequently rises. New calculations by researchers from the Niels Bohr Institute show that the sea level in Northern Europe may rise more than previously thought.

Renewable energy's record year helps uncouple growth of global economy and CO2 emissions
Renewable energy targets and other support policies now in place in 164 countries powered the growth of solar, wind and other green technologies to record-breaking energy generation capacity in 2014.

A new method of converting algal oil to transportation fuels
A new method of converting squalene, which is produced by microalgae, to gasoline or jet fuel, has been developed by the research group of Professor Keiichi Tomishige and Dr. Yoshinao Nakagawa from Tohoku University's Department of Applied Chemistry, and Dr. Hideo Watanabe from the University of Tsukuba.

Boreal peatlands not a global warming time bomb
To some scientists studying climate change, boreal peatlands are considered a potential ticking time bomb. With huge stores of carbon in peat, the fear is that rising global temperatures could cause the release of massive amounts of CO2 from the peatlands into the atmosphere--essentially creating a greenhouse gas feedback loop.

Plants may run out of time to grow under ongoing climate change
A key potential 'benefit' of global warming--namely, that plants at northern latitudes will thrive in a warmer world--is challenged by a new study released by University of Hawai'i scientists today.

What would it take to limit climate change to 1.5°C?
Limiting temperature rise by 2100 to less than 1.5°C is feasible, at least from a purely technological standpoint, according to the study published in the journal Nature Climate Change by researchers at the International Institute for Applied Systems Analysis (IIASA), the Potsdam Institute for Climate Impact Research (PIK), and others.

Cold-blooded animals find it hard to adjust to global warming
Cold-blooded and other animals that are unable to regulate their internal temperature may have a hard time tolerating global warming, according to an analysis by biologists from the University of California, Berkeley, and San Francisco State University.

Climate change could cause cold-blooded animals' thermal tolerance to shrink
Cold-blooded animals can tolerate body temperatures only a few degrees above their normal high temperatures before they overheat, which could be a problem as the planet itself warms, according to San Francisco State University researchers.
More Global Warming Current Events and Global Warming News Articles

Climate Change: Evidence and Causes (PDF Booklet)

Climate Change: Evidence and Causes (PDF Booklet)
by National Academies Press


Climate Change: Evidence and Causes is a jointly produced publication of The US National Academy of Sciences and The Royal Society. Written by a UK-US team of leading climate scientists and reviewed by climate scientists and others, the publication is intended as a brief, readable reference document for decision makers, policy makers, educators, and other individuals seeking authoritative information on the some of the questions that continue to be asked. Climate Change makes clear what is well-established and where understanding is still developing. It echoes and builds upon the long history of climate-related work from both national academies, as well as on the newest climate-change assessment from the United Nations' Intergovernmental Panel on Climate Change. It touches on current...

Climate Change: The Facts

Climate Change: The Facts
by J.Abbot (Author), J.S. Armstrong (Author), A.Bolt (Author), R.Carter (Author), R.Darwall (Author), J.Delingpole (Author), C.Essex (Author), S.Franks (Author), K.Green (Author), D.Laframboise (Author), N.Lawson (Author), B.Lewin (Author), R.Lindzen (Author), J.Marohasy (Author), R.McKitrick (Author), P.Michaels (Author), A.Moran (Author), J.Nova (Author), G.Paltridge (Author), I.Plimer (Author), W.Soon (Author), M.Steyn (Author), A.Watts (Author), Alan Moran (Editor)


Tirelessly promoted by princes, presidents, actors and activists, "climate change" has become a dominant theme of global politics. But what's really going on as the "pause" in global warming prepares to enter its third decade? In this new anthology, leading scientists and commentators from the United States, the United Kingdom, Canada and Australia consider the climate from every angle - the science, the policy and the politics.

The Great Global Warming Blunder: How Mother Nature Fooled the World’s Top Climate Scientists

The Great Global Warming Blunder: How Mother Nature Fooled the World’s Top Climate Scientists
by Roy W Spencer (Author)


The Great Global Warming Blunder unveils new evidence from major scientific findings that explode the conventional wisdom on climate change and reshape the global warming debate as we know it. Roy W. Spencer, a former senior NASA climatologist, reveals how climate researchers have mistaken cause and effect when analyzing cloud behavior and have been duped by Mother Nature into believing the Earth’s climate system is far more sensitive to human activities and carbon dioxide than it really is.

In fact, Spencer presents astonishing new evidence that recent warming is not the fault of humans, but the result of chaotic, internal natural cycles that have been causing periods of warming and cooling for millennia. More carbon dioxide in the atmosphere is not necessarily to be feared; The...

Global Warming-Alarmists, Skeptics and Deniers: A Geoscientist Looks at the Science of Climate Change

Global Warming-Alarmists, Skeptics and Deniers: A Geoscientist Looks at the Science of Climate Change
by G. Dedrick Robinson (Author), Gene D. Robinson III (Author)


Global Warming-Alarmists, Skeptics & Deniers: A Geoscientist looks at the Science of Climate Change, brings a unique geological perspective to this politically charged issue, a perspective that has been ignored far too long. Written by a father-son team of geoscientist and attorney, it is the concise guide to the global warming controversy that has been long needed. As a university professor and research geologist for thirty years, Dr. Robinson knows that geological science is essential for placing the global warming controversy in proper prospective. One cannot hope to understand how humans might be causing climate change without an understanding of the magnitude and speed natural processed are capable of when it comes to climate change. Earth history is the only yardstick we have to...

The Sixth Extinction: An Unnatural History

The Sixth Extinction: An Unnatural History
by Elizabeth Kolbert (Author)


Over the last half a billion years, there have been five mass extinctions of life on earth. Scientists around the world are currently monitoring the sixth, predicted to be the most devastating extinction event since the asteroid impact that wiped out the dinosaurs. Elizabeth Kolbert combines brilliant field reporting, the history of ideas and the work of geologists, botanists and marine biologists to tell the gripping stories of a dozen species - including the Panamanian golden frog and the Sumatran rhino - some already gone, others at the point of vanishing. The sixth extinction is likely to be mankind's most lasting legacy and Elizabeth Kolbert's book urgently compels us to rethink the fundamental question of what it means to be human.

This Changes Everything: Capitalism vs. The Climate

This Changes Everything: Capitalism vs. The Climate
by Naomi Klein (Author)


The most important book yet from the author of the international bestseller The Shock Doctrine, a brilliant explanation of why the climate crisis challenges us to abandon the core “free market” ideology of our time, restructure the global economy, and remake our political systems.

In short, either we embrace radical change ourselves or radical changes will be visited upon our physical world. The status quo is no longer an option.

In This Changes Everything Naomi Klein argues that climate change isn’t just another issue to be neatly filed between taxes and health care. It’s an alarm that calls us to fix an economic system that is already failing us in many ways. Klein meticulously builds the case for how massively reducing our greenhouse emissions is our best chance...

Windfall: The Booming Business of Global Warming

Windfall: The Booming Business of Global Warming
by Mckenzie Funk (Author)


A fascinating investigation into how people around the globe are cashing in on a warming world

McKenzie Funk has spent the last six years reporting around the world on how we are preparing for a warmer planet. Funk shows us that the best way to understand the catastrophe of global warming is to see it through the eyes of those who see it most clearly—as a market opportunity.

Global warming’s physical impacts can be separated into three broad categories: melt, drought, and deluge. Funk travels to two dozen countries to profile entrepreneurial people who see in each of these forces a potential windfall.

The melt is a boon for newly arable, mineral-rich regions of the Arctic, such as Greenland—and for the surprising kings of the manmade snow trade, the Israelis....

Merchants of Doubt: How a Handful of Scientists Obscured the Truth on Issues from Tobacco Smoke to Global Warming

Merchants of Doubt: How a Handful of Scientists Obscured the Truth on Issues from Tobacco Smoke to Global Warming
by Naomi Oreskes (Author), Erik M. Conway (Author)


The U.S. scientific community has long led the world in research on such areas as public health, environmental science, and issues affecting quality of life. These scientists have produced landmark studies on the dangers of DDT, tobacco smoke, acid rain, and global warming. But at the same time, a small yet potent subset of this community leads the world in vehement denial of these dangers. Merchants of Doubt tells the story of how a loose-knit group of high-level scientists and scientific advisers, with deep connections in politics and industry, ran effective campaigns to mislead the public and deny well-established scientific knowledge over four decades. Remarkably, the same individuals surface repeatedly-some of the same figures who have claimed that the science of global warming is...

Global Warming

Global Warming
by Seymour Simon (Author)


Award-winning science writer Seymour Simon gives you a full-color photographic introduction to the causes and effects of global warming and climate change. Earth's climate has always varied, but it is now changing more rapidly than at any other time in recent centuries. The climate is very complex, and many factors play important roles in determining how it changes. Why is the climate changing? Could Earth be getting warmer by itself? Are people doing things that make the climate warmer?Supports the Common Core State Standards

The Global Warming Reader: A Century of Writing About Climate Change

The Global Warming Reader: A Century of Writing About Climate Change
by Bill McKibben (Author)


Our most widely respected environmental writer brings together the essential voices on global warming, from its 19th-century discovery to the present
With the rise of extreme weather events worldwide--witness the devastation wrought by Hurricanes Sandy, Irene, and Katrina, and the sustained drought across the American West--global warming has become increasingly difficult to deny.

What is happening to our planet? And what can we do about it? The Global Warming Reader provides more than thirty-five answers to these burning questions, from more than one hundred years of engagement with the topic. Here is Elizabeth Kolbert's groundbreaking essay "The Darkening Sea," Michael Crichton's skeptical view of climate change, George Monbiot's biting indictment of those who are really using...

© 2015 BrightSurf.com