According to a new report by the National Oceanic and Atmospheric Administration (NOAA), 2011 was the coldest year since 2008 and had more extreme weather events than average. The report, compiled by scientists from 48 different countries and issued by the NOAA and the American Meteorological Society (AMS), reports that much of the extreme and cold weather in 2011 can be explained by two back-to-back La Niña events. La Niña is a weather pattern characterized by cooler-than-normal weather conditions in the equatorial Pacific Ocean.
Some of the out-of-the-ordinary weather events from 2011 include droughts in East Africa, northern Mexico, and the Southern United States. The two La Niña events also contributed to the increased severity of the North Atlantic cyclone season and historic highs in rainfall in Australia following ten years of dry weather.
The report includes a detailed look at climate conditions around the world, mostly based on data collected from environmental monitoring stations. The writers of the report used 43 different climate indicators, including greenhouse gas concentration, atmospheric temperatures, sea levels, and snow cover.
Many of the report’s findings show that global warming trends are not stopping. In spite of being the coolest year since 2008, 2011 was also one of the 15 warmest years since the recording of temperatures started late in the 19th century. A measuring station at the South Pole recorded its highest temperature ever: 9.9 degrees Fahrenheit. The report also shows an increase in greenhouse gases, ocean salinity, and ocean surface temperatures accompanied by a decrease in Arctic sea ice extent and Arctic ozone levels.
In addition to these trends, the report also mentions a number of aberrant weather events from around the world, such as flooding in Thailand and deadly tornadoes in the United States.
Deputy NOAA Administrator Kathryn D. Sullivan says that “2011 will be remembered as a year of extreme events, both in the United States and around the world” and that “every weather event that happens now takes place in the context of a changing global environment. This annual report provides scientists and citizens alike with an analysis of what has happened so we can all prepare for what is to come.”
The AMS published a supplementary article focusing on six specific weather events from last year. The focus of the AMS report is linking particular extreme weather events to large-scale climate changes. One of the findings, for instance, is that La Niña-related heat waves are about 20 times more likely to occur in the context of today’s weather conditions than during La Niña weather patterns fifty years ago. The exact causal links between extreme weather events and global trends, according to the report, are often difficult to determine exactly.