 |
|
The Arctic offers more evidence of human influences on climate change
September 04, 2009Recent, sudden and dramatic Arctic warming was preceded by almost 2,000 years of natural cooling
A new study indicates that Arctic temperatures suddenly increased during the last 50 years of the period from 1 AD to the year 2000. Because this warming occurred abruptly during the 20th Century while atmospheric greenhouse gases were accumulating, these findings provide additional evidence that humans are influencing climate.
Incorporating geologic records, biologic records and computer simulations, the study reconstructed Arctic summer temperatures at a resolution down to decades, and thereby extends the climate record a full 1,600 years beyond the 400 year-long record that was previously available at that resolution. This newly lengthened record shows that recent warming was preceded by a cooling trend that lasted at least 1,900 years and should have continued throughout the 20th Century. These results indicate that recent warming is more anomalous than previously documented, says Darrell Kaufman of Northern Arizona University--the lead author of the study.
Conducted by an international team of scientists and primarily funded by the National Science Foundation (NSF), the study is described in the September 4, 2009, issue of Science.
Kaufman says that the results of his team's study are significant not only because of their implications for our understanding of human influences on climate change, but also because they agree with the National Center for Atmospheric Research's (NCAR) climate model, which is used for predicting future climate change; this agreement increases confidence in the model's simulations of future climate change.
Recent warming reversed long-term cooling
Specifically, the Kaufman et al. study is the first to quantify at a decadal resolution a pervasive cooling across the Arctic from the early part of the first millennium AD to the industrial revolution, according to Kaufman. During this period, summer temperatures in the Arctic cooled at a rate of about 0.2 degrees Celsius per millennium, leading to the 'Little Ice Age', a period of sustained cold that ended around 1850.
"Scientists have known for a while that the current period of warming was preceded by a long-term cooling trend," says Kaufman. "But our reconstruction quantifies the cooling with greater certainty than before."
The researchers believe that the long cooling trend was caused by a previously recognized wobble in the Earth's axis of rotation that slowly increased the distance between the Earth and the Sun during the Arctic summer, and thereby reduced summer sunshine in the Arctic. (See figure.) But even though this cooling wobble persisted throughout the 20th Century, by the middle of the 20th Century, summer temperatures in the Arctic were about 0.7 degrees Celsius (33.3 degrees Fahrenheit) higher than would have been expected if the cooling trend had continued. This incongruity provides evidence of human influences on climate change, says Kaufman.
What's more, the results of the Kaufman et al. study together with recent records of thermometer readings indicate that the last decade was the warmest of the last two millennia--with Arctic temperatures averaging about 1.4 degrees Celsius (34.5 degrees Fahrenheit) higher than would have been expected if the cooling trend had continued, according to Kaufman.
Arctic sensitivity to climate change
Kaufman says that his team's study agrees with previous studies that have shown that Arctic temperatures increased during the 20th Century almost three times faster than temperatures increased throughout the rest of the Northern Hemisphere. Called arctic amplification, this phenomenon is caused by increases in the Arctic's absorption of the sun's heat by dark land and exposed ocean as Arctic ice and snow melt away. "The ability of such a slight wobble in the Earth's axis to cause a significant temperature change over the 1,900 year period preceding the onset of recent warming provides further evidence of the sensitivity of the Arctic's climate system," says Kaufman.
"Because we know that the processes responsible for past arctic amplification are still operating, we can anticipate that it will continue into the next century," says Gifford Miller of the University of Colorado, Boulder, a member of the study team. "Consequently, Arctic warming will continue to exceed temperature increases in the rest of the Northern Hemisphere, resulting in accelerated loss of land ice and an increased rate of sea-level rise, with global consequences."
Real-world records of climate change
The 2000-year reconstruction of Arctic temperatures provided by the Kaufman et al. study incorporated three types of field-based data--each of which captured the response of a different component of the Arctic's climate system to changes in temperature.
These field-based data included temperature reconstructions that were published by the Kaufman et al. team earlier this year. These reconstructions were based on evidence provided by sediments from Arctic lakes, including algal abundance, which reflects the length of the growing season, and the thickness of annually deposited sediment layers, which increases during warmer summers when deposits from glacial melt-water increase. The Kaufman et al. study also incorporated previously published data from glacial ice and tree rings that was calibrated against the instrumental temperature record.
Computer models of climate change
The Kaufman et al. study also included a 2,000 year-long computer simulation of climate change that incorporated the Earth's slow rotational wobble and resulting reduction in seasonal sunlight in the Arctic. Because the model's estimate of the amount of cooling resulting from the wobble effect matched the cooling reflected in the long record of climate change provided by lake sediments and other natural archives, this analysis increased confidence in the model's ability to accurately predict temperature responses in the Arctic to factors that influence climate change. "This result is particularly important because the Arctic is perhaps the most sensitive area of the Earth to the human factors that influence climate change," says David Schneider of NCAR, who is a member of the research team.
"As we are confronted with evidence of global warming, it is extremely helpful to be able to use paleoclimate data to provide context for today's climate relative to the range and trajectory of recent climate regimes," says Neil Swanberg, director of NSF's Arctic System Science Program. "This reconstruction uses a variety of data sources to extend high resolution records back in time sufficiently long to compare reconstructed temperatures to those from models that include changes in insolation due to changes in the Earth's orbital patterns. That the results appear to match so well increases our confidence in our understanding of the processes that are impacting the global Earth system."
National Science Foundation
Conducted by an international team of scientists and primarily funded by the National Science Foundation (NSF), the study is described in the September 4, 2009, issue of Science.
Kaufman says that the results of his team's study are significant not only because of their implications for our understanding of human influences on climate change, but also because they agree with the National Center for Atmospheric Research's (NCAR) climate model, which is used for predicting future climate change; this agreement increases confidence in the model's simulations of future climate change.
Recent warming reversed long-term cooling
Specifically, the Kaufman et al. study is the first to quantify at a decadal resolution a pervasive cooling across the Arctic from the early part of the first millennium AD to the industrial revolution, according to Kaufman. During this period, summer temperatures in the Arctic cooled at a rate of about 0.2 degrees Celsius per millennium, leading to the 'Little Ice Age', a period of sustained cold that ended around 1850.
"Scientists have known for a while that the current period of warming was preceded by a long-term cooling trend," says Kaufman. "But our reconstruction quantifies the cooling with greater certainty than before."
The researchers believe that the long cooling trend was caused by a previously recognized wobble in the Earth's axis of rotation that slowly increased the distance between the Earth and the Sun during the Arctic summer, and thereby reduced summer sunshine in the Arctic. (See figure.) But even though this cooling wobble persisted throughout the 20th Century, by the middle of the 20th Century, summer temperatures in the Arctic were about 0.7 degrees Celsius (33.3 degrees Fahrenheit) higher than would have been expected if the cooling trend had continued. This incongruity provides evidence of human influences on climate change, says Kaufman.
What's more, the results of the Kaufman et al. study together with recent records of thermometer readings indicate that the last decade was the warmest of the last two millennia--with Arctic temperatures averaging about 1.4 degrees Celsius (34.5 degrees Fahrenheit) higher than would have been expected if the cooling trend had continued, according to Kaufman.
Arctic sensitivity to climate change
Kaufman says that his team's study agrees with previous studies that have shown that Arctic temperatures increased during the 20th Century almost three times faster than temperatures increased throughout the rest of the Northern Hemisphere. Called arctic amplification, this phenomenon is caused by increases in the Arctic's absorption of the sun's heat by dark land and exposed ocean as Arctic ice and snow melt away. "The ability of such a slight wobble in the Earth's axis to cause a significant temperature change over the 1,900 year period preceding the onset of recent warming provides further evidence of the sensitivity of the Arctic's climate system," says Kaufman.
"Because we know that the processes responsible for past arctic amplification are still operating, we can anticipate that it will continue into the next century," says Gifford Miller of the University of Colorado, Boulder, a member of the study team. "Consequently, Arctic warming will continue to exceed temperature increases in the rest of the Northern Hemisphere, resulting in accelerated loss of land ice and an increased rate of sea-level rise, with global consequences."
Real-world records of climate change
The 2000-year reconstruction of Arctic temperatures provided by the Kaufman et al. study incorporated three types of field-based data--each of which captured the response of a different component of the Arctic's climate system to changes in temperature.
These field-based data included temperature reconstructions that were published by the Kaufman et al. team earlier this year. These reconstructions were based on evidence provided by sediments from Arctic lakes, including algal abundance, which reflects the length of the growing season, and the thickness of annually deposited sediment layers, which increases during warmer summers when deposits from glacial melt-water increase. The Kaufman et al. study also incorporated previously published data from glacial ice and tree rings that was calibrated against the instrumental temperature record.
Computer models of climate change
The Kaufman et al. study also included a 2,000 year-long computer simulation of climate change that incorporated the Earth's slow rotational wobble and resulting reduction in seasonal sunlight in the Arctic. Because the model's estimate of the amount of cooling resulting from the wobble effect matched the cooling reflected in the long record of climate change provided by lake sediments and other natural archives, this analysis increased confidence in the model's ability to accurately predict temperature responses in the Arctic to factors that influence climate change. "This result is particularly important because the Arctic is perhaps the most sensitive area of the Earth to the human factors that influence climate change," says David Schneider of NCAR, who is a member of the research team.
"As we are confronted with evidence of global warming, it is extremely helpful to be able to use paleoclimate data to provide context for today's climate relative to the range and trajectory of recent climate regimes," says Neil Swanberg, director of NSF's Arctic System Science Program. "This reconstruction uses a variety of data sources to extend high resolution records back in time sufficiently long to compare reconstructed temperatures to those from models that include changes in insolation due to changes in the Earth's orbital patterns. That the results appear to match so well increases our confidence in our understanding of the processes that are impacting the global Earth system."
National Science Foundation
Climate Change Current Events and Climate Change News RSSScientists at UA, collaborating institutions decode maize genome
Scientists from the University of Arizona led by Arizona Genomics Institute director Rod A. Wing and from collaborating institutions have deciphered the complete genetic code of the maize plant for the first time.
ORNL, Los Alamos pioneer new approach to assist scientists, farmers
Sustainable farming, initially adopted to preserve soil quality for future generations, may also play a role in maintaining a healthy climate, according to researchers at the Department of Energy's Oak Ridge and Los Alamos national laboratories.
Research challenges for understanding landscape changes identified
Nine research challenges and four research initiatives that are poised to advance the study of how Earth's landscapes change were unveiled today in a new report by the National Research Council.
Berkeley Lab Lends Expertise to India to Promote Energy Efficiency
ndia may rank only a distant fourth in terms of carbon dioxide emissions, behind China, the United States and Russia, but its rapid economic growth rate coupled with aging and inefficient energy infrastructure suggest dire environmental consequences if "business as usual" continues.
Experts: Failure to focus on farming will undermine global climate agreement and increase hunger
Alarmed by a substantial oversight in the global climate talks leading up to the United Nations Climate Change Conference in Copenhagen next month, more than 60 of the world's most prominent agricultural scientists and leaders underscored how the almost total absence of agriculture in the agreement could lead to widespread famine and food shortages in the years ahead.
Study: Sea stars bulk up to beat the heat
A new study finds that a species of sea star stays cool using a strategy never before seen in the animal kingdom. The sea stars soak up cold sea water into their bodies during high tide as buffer against potentially damaging temperatures brought about by direct sunlight at low tide.
Emulating Western lifestyles: Consumption and carbon footprints in less industrialized countries
In recent decades, a new global middle class has exploded, with a total population exceeding one billion people. A new study in the Journal of Consumer Research explores the consumption attitudes of some of these members of the "new class."
TEEB report released on the economics of ecosystems and biodiversity for policy makers
Policy makers who factor the planet's multi-trillion dollar ecosystem services into their national and international investment strategies are likely to see far higher rates of return and stronger economic growth in the 21st century.
New Water Management Tool May Help Ease Effects of Drought
Continued improvement of climate forecasts is resulting in better information about what rainfall and streamflow may look like months in advance.
Record highs far outpace record lows across US
Spurred by a warming climate, daily record high temperatures occurred twice as often as record lows over the last decade across the continental United States, new research shows.
More Climate Change Current Events and Climate Change News Articles
 |
Climate Change: Picturing the Science by Gavin Schmidt (Author), Joshua Wolfe (Author), Jeffrey D. Sachs (Foreword) An unprecedented union of scientific analysis and stunning photography illustrating the effects of climate change on the global ecosystem. Going beyond the headlines, this work by leading NASA climate scientist Gavin Schmidt and master photographer Joshua Wolfe illustrates as never before the ramifications of shifting climate. Photographic spreads show retreating glaciers, sinking villages in Alaska’s tundra, and drying lakes. The text follows adventurous scientists through the ice caps at the poles to the coral reefs of the tropical seas. Marshaling data spanning centuries and continents, the book sparkles with cutting-edge research and visual records, including contributions from experts on atmospheric science, oceanography, paleoclimatology, technology, politics, and... |
 |
The Rough Guide to Climate Change, 2nd Edition by Robert Henson (Author) The Rough Guide to Climate Change gives the complete picture of the single biggest issue facing the planet. Cutting a swathe through scientific research and political debate, this completely updated 2nd edition lays out the facts and assesses the options- global and personal- for dealing with the threat of a warming world. The guide looks at the evolution of our atmosphere over the last 4.5 billion years and what computer simulations of climate change reveal about our past, present, and future. This updated edition includes new information from the 2007 report from the Intergovernmental Panel on Climate Change and an updated politics section to reflect post-Kyoto developments. Discover how rising temperatures and sea levels, plus changes to extreme weather patterns, are already affecting... |
 |
Climate Change: A Multidisciplinary Approach by William James Burroughs (Author) Providing a concise, up-to-date presentation of current knowledge of climate change and its implications for society as a whole, this new edition has been thoroughly updated and extended to include the latest information. The text describes the components of the global climate, considers how the many elements of climate combine to define its behaviour, and reviews how climate change is measured. The author discusses how the causes of climate change can be related to the evidence of change, and modelled to predict future changes. This book is ideally suited for introductory courses in meteorology, oceanography, environmental science, earth science, geography, agriculture and social science. It contains review questions at the end of each chapter to enable readers to monitor their... |
 |
The Science and Politics of Global Climate Change: A Guide to the Debate by Andrew E. Dessler (Author), Edward A. Parson (Author) Climate variability has become the primary environmental concern of the 21st Century. Yet, despite the scientific community's warnings of the imminent dangers of global warming, politicians world-wide have failed to agree on what to do about this potentially devastating environmental problem. This introductory primer informs scientists, policy makers and the general public by clarifying the conflicting claims of the debate. |
 |
What We Know About Climate Change (Boston Review Books) by Kerry Emanuel (Author), Judith A. Layzer (Afterword), William R. Moomaw (Afterword) The vast majority of scientists agree that human activity has significantly increased greenhouse gases in the atmosphere—most dramatically since the 1970s. In February 2007 the Intergovernmental Panel on Climate Change found that global warming is "unequivocal" and that human-produced carbon dioxide and other greenhouse gases are chiefly to blame, to a certainty of more than 90 percent. Yet global warming skeptics and ill-informed elected officials continue to dismiss this broad scientific consensus. In What We Know About Climate Change, MIT atmospheric scientist Kerry Emanuel outlines the basic science of global warming and how the current consensus has emerged. Although it is impossible to predict exactly when the most dramatic effects of global warming will be felt, he argues, we can... |
 |
Climate Change: The Science of Global Warming and Our Energy Future by Edmond A. Mathez (Author) Climate Change is geared toward a variety of students and general readers who seek the real science behind global warming. Exquisitely illustrated, the text introduces the basic science underlying both the natural progress of climate change and the effect of human activity on the deteriorating health of our planet. Noted expert and author Edmond A. Mathez synthesizes the work of leading scholars in climatology and related fields, and he concludes with an extensive chapter on energy production, anchoring this volume in economic and technological realities and suggesting ways to reduce greenhouse-gas emissions. Climate Change opens with the climate system fundamentals: the workings of the atmosphere and ocean, their chemical interactions via the carbon cycle, and the scientific... |
 |
The Ethics of Climate Change: Right and Wrong in a Warming World (Think Now) by James Garvey (Author) The debate about the existence of climate change seems finally at an end. We now have to decide what to do about it. Here, James Garvey argues that the ultimate rationale for action on climate change cannot be simply economic, political, scientific or social, though no doubt our decisions should be informed by such things. Instead, climate change is largely a moral problem. What we should do about it depends on what matters to us and what we think is right.This book is an introduction to the ethics of climate change. It considers a little climate science and a lot of moral philosophy, ultimately finding a way into the many possible positions associated with climate change. It is also a call for action, for doing something about the moral demands placed on both governments and individuals... |
 |
The Atlas of Climate Change: Mapping the World's Greatest Challenge (Atlas Of... (University of California Press)) by Kirstin Dow (Author), Thomas Downing (Author) Today's headlines and recent events reflect the gravity of climate change. Heat waves, droughts, and floods are bringing death to vulnerable populations, destroying livelihoods, and driving people from their homes. Rigorous in its science and insightful in its message, this atlas examines the causes of climate change and considers its possible impact on subsistence, water resources, ecosystems, biodiversity, health, coastal megacities, and cultural treasures. It reviews historical contributions to greenhouse gas levels, progress in meeting international commitments, and local efforts to meet the challenge of climate change. With more than 50 full-color maps and graphics, this is an essential resource for policy makers, environmentalists, students, and everyone concerned with this... |
 |
Climate Confusion: How Global Warming Hysteria Leads to Bad Science, Pandering Politicians and Misguided Policies that Hurt the Poor by Roy Spencer (Author) The current frenzy over global warming has galvanized the public and cost taxpayers billons of dollars in federal expenditures for climate research. It has spawned Hollywood blockbusters and inspired major political movements. It has given a higher calling to celebrities and built a lucrative industry for scores of eager scientists. In short, ending climate change has become a national crusade. And yet, despite this dominant and sprawling campaign, the facts behind global warming remain as confounding as ever. In Climate Confusion, distinguished climatologist Dr. Roy Spencer observes that our obsession with global warming has only clouded the issue. Forsaking blindingly technical statistics and doomsday scenarios, Dr. Spencer explains in simple terms how the climate system... |
 |
Climate Change (DK Eyewitness Books) by John Woodward (Author) The most trusted nonfiction series on the market, Eyewitness Books provide an in-depth, comprehensive look at their subjects with a unique integration of words and pictures. An in-depth look at the phenomenon of global warming--what's causing it, what it might lead to, and what we can do to fight back. |
| © 2009 BrightSurf.com |