Last year was one of the warmest on record, according to separate analyses of global temperature data by NASA and NOAA. Though they differ in ranking, both federal agencies placed 2013 among the top 10 warmest years since records began in 1880, continuing a longer-term trend of global warming. (The NASA animation above shows temperature variations from average from 1950-2013.)
While we’re shivering through another deep freeze from the northern Plains to the East Coast of the U.S., it’s worth noting not everyone had a particularly warm year: 2013 was just the 42nd warmest year on record for the United States, according to the report from NASA’s Goddard Institute for Space Studies. Australia, however, had its hottest year ever.
“Long-term trends in surface temperatures are unusual and 2013 adds to the evidence for ongoing climate change,” Goddard climatologist Gavin Schmidt said. “While one year or one season can be affected by random weather events, this analysis shows the necessity for continued, long-term monitoring.”
NOAA pegged 2013 as the fourth warmest year globally (tied with 2003). The agency said the combined land and ocean surface temperature was 0.62°C (1.12°F) above the 20th century average of 13.9°C (57.0°F). The average is calculated for a base period of 1951-1980. NASA ranked the year as tied for seventh warmest, based on a slightly different method.
Some other benchmarks noted by NOAA:
- This marks the 37th consecutive year that the yearly global temperature was above average (based on the period from 1951-1980). The warmest year on record is 2010, which was 0.66°C (1.19°F) above average.
- Nine of the 10 warmest years in the 134-year period of record have occurred in the 21st century. Only one year during the 20th century—1998—was warmer than 2013.
“Scientists emphasize that weather patterns always will cause fluctuations in average temperatures from year to year, but the continued increases in greenhouse gas levels in Earth’s atmosphere are driving a long-term rise in global temperatures,” NASA-GISS said in a statement. “Each successive year will not necessarily be warmer than the year before, but with the current level of greenhouse gas emissions, scientists expect each successive decade to be warmer than the previous.”
Earth Institute climate scientist James Hansen, former head of the Goddard Institute for Space Studies, and colleagues Makiko Sato and Reto Ruedy did an analysis of the temperature data and projected that we will probably see a record warm year this year or next. The paper examines the roles of natural variability and human activity and other phenomena forcing shifts in the climate. They note that the rate of global warming has slowed in the past decade, but say the overall trend continues. Because temperature variability tends to be much higher in winter than in summer, the paper says, it is easier to recognize the effects of global warming in summer.
December was much colder than normal in North America, and as that led into a January deep freeze, some in the media used the cold weather as a basis to question whether global warming is really happening. But, the Hansen paper says, December’s globally averaged temperatures were still above “normal,” by 0.6°C.
The increase in man-made greenhouse gas emissions over the past century plays a key role in the warming trend, and has pushed the level of carbon dioxide in Earth’s atmosphere higher than at any time in the last 800,000 years, according to NASA. CO2 levels were about 285 parts per million in 1880, the first year in the NASA-GISS temperature record. Last year, the level peaked at more than 400 parts per million, as measured at NOAA’s Mauna Loa Observatory in Hawaii.
NASA has posted a web page with several relevant temperature maps, charts and comparisons of how that agency and NOAA rank the warmest years.
NOAA has posted a world map showing details of out-of-the-ordinary weather and climate events in 2013.