Global Warming Facts

NASA Global Warming Facts: 2009 - Second Warmest Year on Record; End of Warmest Decade

Global climate change ... NASA's eyes on the Earth: A warming world - global temperature update ... piecing together the temperature puzzle.

Each year, scientists at NASA'S Goddard Institute for Space Studies analyze global temperature data. The past year, 2009, tied as the second warmest year since global instrumental temperature records began 130 years ago. Worldwide, the mean temperature was 0.57°C (1.03°F) warmer than the 1951-1980 base period. And January 2000 to December 2009 came out as the warmest decade on record.

• http://climate.nasa.gov/warmingworld

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2009 was tied for the second warmest year in the modern record, a new NASA analysis of global surface temperature shows. The analysis, conducted by the Goddard Institute for Space Studies (GISS) in New York City, also shows that in the Southern Hemisphere, 2009 was the warmest year since modern records began in 1880.

Although 2008 was the coolest year of the decade, due to strong cooling of the tropical Pacific Ocean, 2009 saw a return to near-record global temperatures. The past year was only a fraction of a degree cooler than 2005, the warmest year on record, and tied with a cluster of other years — 1998, 2002, 2003, 2006 and 2007 1998 and 2007 — as the second warmest year since recordkeeping began.

"There's always an interest in the annual temperature numbers and on a given year's ranking, but usually that misses the point," said James Hansen, the director of GISS. "There's substantial year-to-year variability of global temperature caused by the tropical El Niño-La Niña cycle. But when we average temperature over five or ten years to minimize that variability, we find that global warming is continuing unabated."

January 2000 to December 2009 was the warmest decade on record. Throughout the last three decades, the GISS surface temperature record shows an upward trend of about 0.2°C (0.36°F) per decade. Since 1880, the year that modern scientific instrumentation became available to monitor temperatures precisely, a clear warming trend is present, though there was a leveling off between the 1940s and 1970s.

The near-record temperatures of 2009 occurred despite an unseasonably cool December in much of North America. High air pressures in the Arctic decreased the east-west flow of the jet stream, while also increasing its tendency to blow from north to south and draw cold air southward from the Arctic. This resulted in an unusual effect that caused frigid air from the Arctic to rush into North America and warmer mid-latitude air to shift toward the north.

"Of course, the contiguous 48 states cover only 1.5 percent of the world area, so the U.S. temperature does not affect the global temperature much,' said Hansen. In total, average global temperatures have increased by about 0.8°C (1.5°F) since 1880.

"That's the important number to keep in mind," said Gavin Schmidt, another GISS climatologist. "In contrast, the difference between, say, the second and sixth warmest years is trivial since the known uncertainty — or noise — in the temperature measurement is larger than some of the differences between the warmest years."

Decoding the Temperature Record: Climate scientists agree that rising levels of carbon dioxide and other greenhouse gases trap incoming heat near the surface of the Earth and are the key factors causing the rise in temperatures since 1880, but these gases are not the only factors that can impact global temperatures.

• http://www.giss.nasa.gov/research/new...

The Ice Mission

ESA's Earth Explorer CryoSat mission is dedicated to precise monitoring of the changes in the thickness of marine ice floating in the polar oceans and variations in the thickness of the vast ice sheets that overlie Greenland and Antarctica.

With the effects of a changing climate fast becoming apparent, particularly in the polar regions, it is increasingly important to understand exactly how Earths ice fields are responding. Diminishing ice cover is frequently cited as an early casualty of global warming and since ice, in turn, plays an important role regulating climate and sea level, the consequences of change are far reaching.

For some years now, satellites such as ESAs Envisat have been mapping the extent of ice cover. As stated in the Climate Change 2007 Synthesis Report by the Intergovernmental Panel on Climate Change, "Satellite data since 1978 show that annual average Arctic sea-ice extent has shrunk by 2.7% per decade." However, this is only part of the picture.

In order to understand fully how climate change is affecting these remote but sensitive regions, there remains an urgent need to determine exactly how the thickness of the ice, both on land and floating in the sea, is changing. By addressing this challenge, the data delivered by the CryoSat mission will complete the picture and lead to a better understanding of the role ice plays in the Earth system.

The CryoSat-2 satellite replaces the original CryoSat, which was lost owing to a launch failure in October 2005. Following the loss, the mission was judged to be even more important than when it was first selected for development, and the decision to rebuild was taken. Almost exactly four years to the day after that decision, the new CryoSat-2, with a number of improvements, was ready for launch.

From an altitude of just over 700 km and reaching latitudes of 88°, the CryoSat-2 satellite will monitor precise changes in the thickness of the polar ice sheets and floating sea ice. CryoSats original objective was to determine if there was a trend towards diminishing ice cover. There now seems little doubt that there are indeed trends the challenge now is to characterise them.

http://www.esa.int/esaLP/LPcryosat.html

Global Temperature Puzzle

The last decade has been measured as the hottest on record all around the globe. This overall result is derived from a patchwork of readings with widely varying effects on local climates. Scientists agree that the change is being spurred by rising levels of carbon dioxide in the atmosphere. This clip was produced by NASA's Goddard Space Flight Center.