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


Researchers discover new producer of crucial vitamin
New research has determined that a single group of micro-organisms may be responsible for much of the world's vitamin B12 production in the oceans, with implications for the global carbon cycle and climate change.

Asian monsoon much older than previously thought
The Asian monsoon already existed 40 million years ago during a period of high atmospheric carbon dioxide and warmer temperatures, reports an international research team led by a University of Arizona geoscientist.

Last decade's slow-down in global warming enhanced by an unusual climate anomaly
A hiatus in global warming ongoing since 2001 is due to a combination of a natural cooling phase, known as multidecadal variability (MDV) and a downturn of the secular warming trend.

The ozone hole has stabilized - some questions remain
The production and consumption of chemical substances threatening the ozone layer has been regulated since 1987 in the Montreal Protocol. Eight international expert reports have since been published, which examine the current situation and the future of the threat to the ozone layer.

Yale Study Shows How Conversion Of Forests to Cropland Affected Climate
The conversion of forests into cropland worldwide has triggered an atmospheric change that, while seldom considered in climate models, has had a net cooling effect on global temperatures, according to a new Yale study.

Study resolves discrepancy in Greenland temperatures during end of last ice age
A new study of three ice cores from Greenland documents the warming of the large ice sheet at the end of the last ice age - resolving a long-standing paradox over when that warming occurred.

To clean air and beyond: Catching greenhouse gases with advanced membranes
Researchers in Japan have engineered a membrane with advanced features capable of removing harmful greenhouse gases from the atmosphere.

Why global warming is taking a break
Global warming is currently taking a break: whereas global temperatures rose drastically into the late 1990s, the global average temperature has risen only slightly since 1998 - surprising, considering scientific climate models predicted considerable warming due to rising greenhouse gas emissions.

Exporting US coal to Asia could drop emissions 21 percent
Under the right scenario, exporting U.S. coal to power plants in South Korea could lead to a 21 percent drop in greenhouse gas emissions compared to burning the fossil fuel at plants in the United States, according to a new Duke University-led study.

Sun's activity influences natural climate change
For the first time, a research team has been able to reconstruct the solar activity at the end of the last ice age, around 20,000-10,000 years ago, by analysing trace elements in ice cores in Greenland and cave formations from China.
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...

Global Warming: Understanding the Forecast

Global Warming: Understanding the Forecast
by David Archer (Author)


Archer's Global Warming: Understanding the Forecast 2nd Edition, is the first real text to present the science and policy surrounding climate change at the right level. Accompanying videos, simulations and instructional support makes it easier to build a syllabus to improve and create new material on climate change. Archer's polished writing style makes the text entertaining while the improved pedagogy helps better understand key concepts, ideas and terms.This edition has been revised and reformulated with a new chapter template of short chapter introductions, study questions at the end, and critical thinking puzzlers throughout. Also a new asset for the BCS was created that will give ideas for assignments and topics for essays and other projects. Furthermore, a number of interactive...

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

Climate Cover-Up: The Crusade to Deny Global Warming

Climate Cover-Up: The Crusade to Deny Global Warming
by James Hoggan (Author), Richard Littlemore (Contributor)


Talk of global warming is nearly inescapable these days — but there are some who believe the concept of climate change is an elaborate hoax. Despite the input of the world’s leading climate scientists, the urgings of politicians, and the outcry of many grassroots activists, many Americans continue to ignore the warning signs of severe climate shifts. How did this happen? Climate Cover-up seeks to answer this question, describing the pollsters and public faces who have crafted careful language to refute the findings of environmental scientists. Exploring the PR techniques, phony "think tanks," and funding used to pervert scientific fact, this book serves as a wake-up call to those who still wish to deny the inconvenient truth.

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 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...

The Age of Global Warming: A History

The Age of Global Warming: A History
by Rupert Darwall (Author)


Rachel Carson's epoch-creating Silent Spring marked the beginnings of the environmental movement in the 1960s, its 'First Wave' peaking at the 1972 Stockholm Conference. The invention of sustainable development by Barbara Ward, along with Rachel Carson the founder of the environmental movement, created an alliance of convenience between First World environmentalism and a Third World set on rapid industrialisation. The First Wave crashed in 1973 with the Yom Kippur War and decade-long energy crisis. Revived by a warming economy of the 1980s, environmentalism found a new, political champion in 1988: Margaret Thatcher. Four years later at the Rio Earth Summit, politics settled the science. One hundred and ninety-two nations agreed that mankind was causing global warming and carbon dioxide...

Global Warming: The Complete Briefing

Global Warming: The Complete Briefing
by John Houghton (Author)


John Houghton's market-leading textbook is now in full color and includes the latest IPCC findings, making it the definitive guide to climate change. Written for students across a wide range of disciplines, its simple, logical flow of ideas gives an invaluable grounding in the science and impacts of climate change and highlights the need for action on global warming. Is there evidence for climate changing due to human activities? How do we account for recent extremes of weather and climate? Can global electricity provision and transport ever be carbon free? Written by a leading figure at the forefront of action to confront humanity's most serious environmental problem, this undergraduate textbook comprehensively explores these and other issues, allowing students to think through the...

The Great Global Warming Blunder: How Mother Nature Fooled the Worldâs 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...

Climategate: A Veteran Meteorologist Exposes the Global Warming Scam

Climategate: A Veteran Meteorologist Exposes the Global Warming Scam
by Brian Sussman (Author)


Those now notorious intercepted emails documenting leading scientists conspiring to squelch global-warming skeptics and falsifying data proved exactly what Brian Sussman has been saying for years. Climategate is intended for anyone who has ever expressed skepticism about the clamorous environmentalist claims that the Earth is in peril because of mankind's appetite for carbon-based fuels. By tracing the origins of the current climate scare, Sussman guides the reader from the diabolical minds of Marx and Engles in the 1800s, to the global governance machinations of the United Nations today. Climategate is a call to action, warning Americans that their future is being undermined by a phony pseudo-science aimed at altering and dominating every aspect of life in the United States and the...

© 2014 BrightSurf.com