Global warming greatest in past decade

September 02, 2008

Researchers confirm that surface temperatures in the Northern Hemisphere were warmer over the last 10 years than any time during the last 1300 years, and, if the climate scientists include the somewhat controversial data derived from tree-ring records, the warming is anomalous for at least 1700 years.

"Some have argued that tree-ring data is unacceptable for this type of study," says Michael Mann, associate professor of meteorology and geosciences and director of Penn State's Earth System Science Center. "Now we can eliminate tree rings and still have enough data from other so-called 'proxies' to derive a long-term Northern Hemisphere temperature record."

The proxies used by the researchers included information from marine and lake sediment cores, ice cores, coral cores and tree rings.

"We looked at a much expanded database and our methods are more sophisticated than those used previously," says Mann. In today's (Sept. 2) online edition of the Proceedings of the National Academy of Sciences, the researchers note, "Conclusions are less definitive for the Southern Hemisphere and globe, which we attribute to larger uncertainties arising from the sparser available proxy data in the Southern Hemisphere."

The research team included Mann; Ray Bradley, university distinguished professor, geosciences and director, Climate System Research Center, University of Massachusetts; Malcolm Hughes, regents' professor, and Fenbiao Ni, research associate, the Laboratory of Tree Ring Research, University of Arizona; Zhihua Zhang and Sonya Miller, research associates, meteorology, Penn State; and Scott Rutherford, assistant professor, environmental sciences, Roger Williams University.

The National Research Council suggested revisiting surface temperatures in their "Surface Temperature Reconstructions for the Last 2,000 Years," to include newer data and techniques and confirmed results of a 1990s paper by Mann and colleagues.

Results of this study without tree-ring data show that for the Northern Hemisphere, the last 10 years are likely unusually warm for not just the past 1,000 as reported in the 1990s paper and others, but for at least another 300 years going back to about A.D. 700 without using tree-ring data. The same conclusion holds back to A.D. 300 if the researchers include tree-ring data.

One of the reasons that including tree-ring data in these studies raises possible concerns is something called the "segment length curse." This "curse" occurs because trees put on rings every year, but older trees put on narrower rings. When tree ring researchers piece together tree-ring series from two trees, they must account for this factor in how they combine the later rings on one tree with the earlier rings on a younger tree. In the process, some information regarding long-term trends can be lost.

"Ten years ago, we could not simply eliminate all the tree-ring data from our network because we did not have enough other proxy climate records to piece together a reliable global record," says Mann. "With the considerably expanded networks of data now available, we can indeed obtain a reliable long-term record without using tree rings."

The new study shows that, with caveats, tree-ring data can be used, but that even without including that data, it is clear that the anomalous nature of recent warmth, which most scientists believe to be a result of human impacts on climate, is a reality.

Penn State

---

---

	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;...
	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...
	Global Warming by Seymour Simon (Author) 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? Award-winning science writer Seymour Simon teams up with the Smithsonian Institution to give you a full-color photographic introduction to the causes and effects of global warming and climate change.
	A-Z of Global Warming by Simon Rosser (Author), Russ Billington (Illustrator) The phrase global warming is a term that has been in common usage for some time and usually refers to recent warming of Earth s atmosphere, which also implies a manmade or human influence. Each chapter of this book deals with an aspect of it. Starting with A for Amazon, the book takes the reader an A-Z journey through global warming, with each chapter dealing with a specific point on the issue of climate change and global warming. Biofuels are looked at, Carbon Dioxide, Electric Vehicles through to Weather, Xtinction, You Can Help and finally Zero Hour.... The book is illustrated throughout to assist in the simplification of this complex subject matter. 10% of authors net sale proceeds will be divided between 4 global warming related organisations, to include The Alliance for Climate...
	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.
	Global Warming False Alarm: The Bad Science Behind the United Nations' Assertion that Man-made CO2 Causes Global Warming by Canterbury Publishing Have you ever wondered why so many people believe recent climate change is almost entirely the result of human activity, even when there's plenty of evidence to the contrary? It's because the UN's Intergovernmental Panel on Climate Change (IPCC) says so. This compact, readable book pulls apart the flawed science behind the IPCC's assertion that man-made CO2 is causing global warming. Author Ralph Alexander exposes the IPCC's deceptive manipulation of climate data, the roadblocks for the CO2 hypothesis favored by climate change alarmists, and the failed predictions of computer climate models. Dr. Alexander goes on to examine the consequences of the erroneous, but widespread belief that CO2 emissions need to be drastically curbed for the health of the planet. His...
	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: Understanding the Forecast by David Archer (Author) Global Warming: Understanding the Forecast is a comprehensive introduction to all aspects of global warming. Written in an accessible style, this important book examines the processes of climate change and climate stability, from the distant past to the distant future.Examining the greenhouse effect, the carbon cycle, and what the future may hold for global climate, this text draws on a wide range of disciplines, and summarizes not only scientific evidence, but also economic and policy issues, related to global warming. A companion web site at (http://understandingtheforecast.org) provides access to interactive computer models of the physics and chemistry behind the global warming forecast, which can be used to support suggested student projects included at the end of each chapter....
	Climategate: A Veteran Meteorologist Exposes the Global Warming Scam by Brian Sussman (Author) Climategate is a godsend for anyone who has ever expressed skepticism about the environmentalist that claim that the Earth is in peril because of mankind's appetite for carbon-based fuels.A distinguished, award-winning television weatherman in San Francisco, Brian Sussman deftly melds easy-to-understand scientific facts with provocative commentary. Sick of twisted "facts" mass-marketed to manipulate basic living decisions and common-sense energy consumption, Sussman indicts a cabal of elitist politicians, bureaucrats and activists who front the environmental movement to push intrusive, Marxist-derived policies in a quest to become filthy rich.By tracing the origins of the current climate scare, Sussman guides the reader from the diabolical minds of Marx and Engels in the 1800s, to the...
	Unstoppable Global Warming: Every 1,500 Years, Updated and Expanded Edition by S. Fred Singer (Author), Dennis T. Avery (Author) Singer and Avery present—in popular language supported by in-depth scientific evidence—the compelling concept that global temperatures have been rising mostly or entirely because of a natural cycle. Using historic data from two millennia of recorded history combined with the natural physical records found in ice cores, seabed sediment, cave stalagmites, and tree rings, Unstoppable Global Warming argues that the 1,500 year solar-driven cycle that has always controlled the earth's climate remains the driving force in the current warming trend. Trillions of dollars spent on reducing fossil fuel use would have no effect on today's rising temperatures. The public policy key, Singer and Avery propose, is adaptation, not fruitless attempts at prevention. Further, they offer...