IPCC 2007 Report

Intergovernmental Panel on Climate Change

Global atmospheric concentrations of carbon dioxide, methane and nitrous oxide have increased markedly as a result of human activities since 1750 and now far exceed pre-industrial values determined from ice cores spanning many thousands of years. The global increases in carbon dioxide concentration are due primarily to fossil fuel use and land-use change, while those of methane and nitrous oxide are primarily due to agriculture.
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The understanding of anthropogenic warming and cooling influences on climate has improved since the Third Assessment Report (TAR), leading to very high confidence that the globally averaged net effect of human activities since 1750 has been one of warming.
summary for policy makers

Sea Level Higher Than Models Predict

Potsdam University
Lead author: Stefan Rahmstorf
Where published: Science Magazine

Global warming could push sea levels about 40 percent higher than current models predict ... observations of changes in sea level collected in the 20th century to make predictions for the 21st century ... results predict that by the end of the century sea level will rise between 20 and 55 inches (50 and 140 centimeters) above 1990 levels ... Reducing greenhouse gas emissions can impact such sea level rise.
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Arctic Ice Retreat

National Center for Atmospheric Research, U.Washington, McGill U.
Lead author: Marika Holland
Where published: Geophysical Research Letters

The recent retreat of Arctic sea ice is likely to accelerate so rapidly that the Arctic Ocean could become nearly devoid of ice during summertime as early as 2040 ... We have already witnessed major losses in sea ice, but our research suggests that the decrease over the next few decades could be far more dramatic than anything that has happened so far.
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Reduced Ocean Life Increasing CO2

Oregon State University, UC Santa Barbara
Lead author: Michael Behrenfeld
Where published: Nature

Alarming new satellite data show that the warming of the world's oceans is reducing ocean life while contributing to increased global warming ... The ocean's food chain is based upon the growth of billions upon billions of microscopic plants. New satellite data show that ocean warming is reducing these plants –– thus imperiling ocean fisheries and marine life
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Global Drought

Hadley Centre for Climate Prediction and Research
Lead Author: Eleanor Burke
Where published: Journal of Hydrometeorology

Drought threatening the lives of millions will spread across half the land surface of the earth in the coming century because of global warming, according to new predictions from Britain's leading climate scientists.

Extreme drought, in which agriculture is effectively impossible, will affect nearly a third of the planet.
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Arctic Ice Retreating

University of Colorado, National Snow and Ice Data Center
Author: Mark Serreze

The total area of surface melt on the Greenland Ice Sheet for 2002 broke all known records for the island and the extent of Arctic sea ice reached the lowest level in the satellite record ... It is likely that sea ice extent will continue to decline over the 21st century as the climate warms. With these trends, we may see an approximate 20 percent reduction in the annual mean sea ice by 2050, and by then we might be approaching no ice at all during the summer months.
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Ice Cores & Greenhouse Gases

Potsdam Institute for Climate Impact Research
Lead author: Thomas Schneider
Where published: Climate Dynamics

Ice Age evidence confirms that a doubling of greenhouse gases could drive up world temperatures by about 3 Celsius (5.4 Fahrenheit), causing havoc with the climate, a study showed on Friday.

The researchers made a novel check of computer climate forecasts about the modern impact of heat-trapping gases, widely blamed on use of fossil fuels, against ice cores and marine sediments from the last Ice Age which ended 10,000 years ago.
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Sunspots Non Impact

Heliophysics, Max Planck Institute for Astrophysics
Lead author: Peter Foukal
Where published: Nature

Sunspots alter the amount of energy Earth gets from the sun, but not enough to impact global climate change ... The difference in brightness between the high point of a sunspot cycle and its low point is less than 0.1 percent of the sun's total output ... If you run that back in time to the 17th century using sunspot records, you'll find that this amplitude variance is negligible for climate.

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Siberian Lakes Bubbling Methane

University of Alaska
Lead author: Katey Walter
Where published: Nature

Global warming is causing Siberian lakes to bubble methane, a greenhouse gas, into the atmosphere at an alarming rate, scientists say. Because methane in the atmosphere warms the planet, the Russian pools are intensifying the climate change that boosted their belching in the first place. It all adds up to a feedback loop in which warming begets even more warming.
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Hurricane Intensity

Florida State
Lead author: James Elsner
Where published: American Geophysical Union

Climate change is affecting the intensity of Atlantic hurricanes, and hurricane damage likely will continue to increase because of greenhouse warming ... future hurricane hazard mitigation efforts should reflect that hurricane damage will continue to increase, in part, due to greenhouse warming
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Undersea Methane

University of California Santa Barbara
Lead author: Ira Leifer
Where published: Global Biogeochemical Cycles

If the world continues to get warmer, vast amounts of methane gas trapped in ice under the sea could belch up and worsen climate change ... The study measured the amount of methane that escaped to the atmosphere ... It found that virtually all of the methane escaping from the deep water reached the atmosphere, countering some theories that methane seeps out in tiny bubbles that harmlessly dissolve in the ocean ... rising temperatures could warm the oceans, creating a feedback loop
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Greenland Ice Melting

University of Texas
Lead author: Byron Tapley
Where Published: Science Magazine

New data shows that Greenland's ice sheets are melting faster than before. Researchers interpreted the data from NASA satellites ... this melting will disrupt the ocean current in the northern hemisphere, which in turn will change the global climate system
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Increasing Methane Levels

Laboratoire des Sciences du Climat et de l'Environnement
Lead author: P. Bousquet
Where published: Nature

Methane is an important greenhouse gas, and its atmospheric concentration has nearly tripled since pre-industrial times ... Remarkably, this growth rate has decreased markedly since the early 1990s, and the level of methane has remained relatively constant since 1999, leading to a downward revision of its projected influence on global temperatures ... Since 1999, however, they indicate that anthropogenic emissions of methane have risen again.
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Increasing Wildfires

Scripps Institution of Oceanography, University of Arizona
Lead author: Dan Cayan

The increase in the number of large western wildfires in recent years may be a result of global warming ... part of the increase may be attributed to natural fluctuations, evidence also links it to the effects of human-induced climate warming
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Seawater Chemistry Altered

National Oceanic and Atmospheric Administration
Lead authors: Richard Feely, Joan Kleypas

Human activities, chiefly the burning of fossil fuels, have upset a natural balance in ocean acidity ... We have very clear evidence, and there is no doubt this is occurring ... Ice core measurements show that oceans have not been as acidic as they now are for at least 650,000 years, and probably millions of years beyond
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Abrupt Warming

Ohio State
Lead author: Lonnie G. Thompson

The warming around Earth's tropical belt is a signal suggesting that the "climate system has exceeded a critical threshold," which has sent tropical-zone glaciers in full retreat and will melt them completely "in the near future"
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Increased Hurricanes

National Center for Atmospheric Research
Lead authors: Kevin Trenberth, Dennis Shea
Where published: Geophysical Research Letters

Global warming provided much of the ocean heat that fueled last year's record-setting hurricane season ... global warming accounted for nearly half of the above-normal ocean heating that fed 15 Atlantic hurricanes ... Natural climate cycles were only a minor factor in the excess warming
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Warmest in 400 Years

National Academy of Science
Chair: Gerald R. North

sufficient evidence from tree rings, boreholes, retreating glaciers, and other "proxies" of past surface temperatures to say with a high level of confidence that the last few decades of the 20th century were warmer than any comparable period in the last 400 years ... scientists' reconstructions of Northern Hemisphere surface temperatures for the past thousand years are generally consistent ... multiple lines of evidence supporting the conclusion that current warming is occurring in response to human activities
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Thawing Permafrost

Russian Academy of Sciences, University of Florida
Lead authors: Sergey Zimov, Edward Schuur
Where Published: Science Magazine

Thawing permafrost in the Arctic could play a role in fueling global warming ... The reservoir is very large and dangerous ... frozen soils across a large swath of Siberia and Alaska hold nearly 500 billion tons (454 billion metric tons) of carbon—or two-thirds current atmospheric levels.
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Hurricane Frequency & Strength

MIT, Penn State
Lead authors: Kerry A. Emanuel, Michael E. Mann
Where published: Eos

Human-induced climate change, rather than naturally occurring ocean cycles, may be responsible for the recent increases in the frequency and strength of North Atlantic hurricanes ... North Atlantic sea surface temperature appears to be controlled largely by radiative forcing, which has changed over the past century mainly owing to sulfate aerosol pollution and greenhouse gas increases
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