Extreme Weather Events, Continued Warming Marked 2010 Climate

By Andrew Freedman

Due in part to rising amounts of greenhouse gases in the atmosphere, the world continued to warm during 2010, as seen through the lens of more than three-dozen climate indicators from the top of the atmosphere to the depths of the ocean. Not only was 2010 among the top two warmest years since reliable surface temperature records began, but it also featured unusual fluctuations in highly influential natural climate cycles such as El Niño, La Niña, and the Arctic Oscillation. These cycles — superimposed on top of a warming planet — helped cause dramatic and devastating weather events worldwide, including record flooding in Australia, a 62-day heat wave in parts of Russia that killed nearly 14,000 people, and deadly flooding in Pakistan that displaced nearly 20 million people. 

Annual average temperature departures from average from 1880 to 2011. Credit: NOAA/NCDC.

All of these events are chronicled in a new, peer-reviewed report released today by the National Oceanic and Atmospheric Administration (NOAA). The “State of the Climate in 2010” report is meant to serve as the official record of last year's climate, and was compiled by an international team of more than 350 scientists from 48 countries and published in the Bulletin of the American Meteorological Society. In the report, scientists document 41 “climate indicators” that help them take the pulse of the planet's climate system, including new additions such as nighttime lake temperatures as measured by satellites, and the amount of water vapor near the earth's surface.

The publication of the State of the Climate report comes as a spate of extreme weather events have left much of the U.S. reeling from natural disaster fatigue in 2011, from record tornado outbreaks in April to record flooding along the Mississippi and Missouri Rivers, and an intense drought accompanied by dangerous wildfires in the Southwestern states.

Although the report does not specifically address the question of whether global warming is increasing the odds of, or otherwise influencing, such extreme events, it clearly depicts broad climate trends and occurrences of individual extreme events that are consistent with what scientists expect to occur as the planet warms.

“[The] Indicators continue to reflect a warming world through the year 2010,” said Tom Karl, director of NOAA's National Climatic Data Center in Asheville, N.C.. Karl said the increase in greenhouse gases such as carbon dioxide (CO2), which trap heat in the atmosphere, is causing much of this warming and is likely to continue to do so. Karl said that emissions of greenhouse gases since 1990 alone have already committed the world to a further temperature increase of between 0.8°F and 2.4°F during the rest of this century. “There’s many indicators to report, but they all reflect a common story of a warming world,” Karl said.

One indicator cited in the report is trends in the Greenland ice sheet. Last year, Greenland's glaciers lost more ice mass than in any other year in the past decade as record warmth enveloped western Greenland. When land-based ice cover melts, it contributes to rising sea levels. The Arctic continued to warm at about twice the rate as the rest of the world, the report states.

The report details some of the events that helped make 2010 memorable as one of the most extreme years in modern history. Here are some highlights:

• The swing from a strong El Niño, which is characterized by warmer than average sea surface temperatures in the equatorial tropical Pacific Ocean, to strong La Niña conditions, featuring cooler than average waters, was one of the most significant on record. Both El Niño and La Niña are credited with contributing to many of the unusual weather patterns in 2010 and into 2011, including the floods in Australia, drought in the Southwestern US, and possibly the flooding in Pakistan.

• Crippling winter snowstorms blasted the East Coast, and several cities had their snowiest February on record, including New York City. These snowstorms were assisted by the sharpest drop in the Arctic Oscillation ever recorded. The Arctic Oscillation, or AO, is a pattern of atmospheric pressure that helps steer the jet stream in the Northern Hemisphere, particularly during the winter. According to Walt Meier of the National Snow and Ice Data Center in Boulder, Colo., researchers are examining the possibility that the loss of Arctic sea ice is altering the behavior of the Arctic Oscillation by warming the Arctic atmosphere and changing the temperature balance between the Far North and areas farther to the south. “[While] there are some tantalizing indications in the last few years that this may have played a role… it’s too early at this point to attribute this to” declining sea ice, he said.

• Arctic sea ice shrank to its third-smallest area on record, opening up both the Northwest Passage and Northern Sea Route for a time. 

• Twelve states in the eastern U.S. experienced their warmest summer on record last year, and this was driven more by warmer than normal nighttime lows than daytime highs. This is consistent with longer-term trends showing that nighttime low temperatures have been increasing faster than daytime highs.

Deke Arndt, chief of NCDC's climate monitoring branch, said although caution is warranted when examining a single year in the climate record, the 2010 data reinforces previously observed trends, rather than going against them. “No single event or single year confirms or refutes what we know about the long-term picture,” he said, adding that it was one of the warmest years on record, occurred during the warmest decade on record, and took place in the context of a sharp warming trend observed during the past 30 years.