January 23, 2012
"We know the planet is absorbing more energy than it is emitting," said NASA's Goddard Institute for Space Studies (GISS) Director James Hansen in a press release. "So we are continuing to see a trend toward higher temperatures. Even with the cooling effects of a strong La Niña influence and low solar activity for the past several years, 2011 was one of the 10 warmest years on record."
The global temperature in 2011 was 0.92 degrees Fahrenheit (0.51 Celsius) degrees warmer than a mid-20th Century baseline. Scientists don't expect every year to be warmer than the last due to climate change, but they do expect to see a warming trend over decades, which has been the case: 2000-2009 was the warmest decade yet on record.
Climate change is caused by human activities that emit greenhouse gases including burning fossil fuels, deforestation, and certain agricultural practices among others. The carbon dioxide level in the atmosphere is currently 390 parts per million, over a hundred parts per million higher than in 1880.
The effects of on-going heat are being felt far-and-wide. Last year saw the Arctic's sea ice hit its lowest volume on record and its second lowest extent. Ice shelves in Canada have halved in the last six years. Meanwhile, with wider recognition of the impacts of climate change on severe weather, this year was also notable for an unusually large amount of extreme weather events. For example, 2011 saw drought and famine in East Africa, killing over tens-of-thousands of people; massive floods in Asia and the Americas with a record-breaking deluge in Thailand, dubbed its worst natural disaster in history; a wide-variety of extreme weather events in the US, including an extended drought and heatwave in Texas; as well as a below-average year for tropical cyclones.
Hansen says he expects an El Niño year soon. The counterpart of La Niña, El Niño usually brings warmer temperatures worldwide.
"It's always dangerous to make predictions about El Niño, but it's safe to say we'll see one in the next three years," Hansen said. "It won't take a very strong El Niño to push temperatures above 2010."
The NOAA recently announced that 2011 was the eleventh warmest year on record, while the UN World Meteorological Organization (WMO) predicted it would be the tenth warmest on record. Slight differences in these records are based on different analysis.
Map shows how much warmer or cooler each region was in 2011 compared with an averaged "base period" from 1951–1980. The line plot shows yearly temperature variations (from the base period average) for every year from 1880 to now. Image by: NASA.
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