An analysis of global temperatures by NASA scientists shows that 2013 was the seventh warmest year since 1880 (tied with 2006 and 2009). Nine of the 10 warmest years on record all have occurred since 2000, with 2010 and 2005 ranking as the warmest. Scientists at NASA’s Goddard Institute for Space Studies (GISS) reported that 2013 continued the long-term trend of rising air temperatures over the land and sea surface.
The top map above depicts global temperature anomalies in 2013. It does not show absolute temperatures, but instead shows how much warmer or cooler the Earth was compared to an averaged base period from 1951 to 1980. The GISS team assembles its analysis with publicly available data from roughly 6,300 meteorological stations around the world; ship-based and satellite observations of sea surface temperature; and Antarctic research station measurements. For more explanation of how the analysis works, read World of Change: Global Temperatures.
The global average temperature for 2013 was 14.6° Celsius (58.3° Fahrenheit), which is 0.6°C (1.1°F) warmer than the mid-20th century baseline. The average global temperature has risen about 0.8°C (1.4°F) since 1880. Exact rankings for individual years are sensitive to data inputs and analysis methods.
“Long-term trends in surface temperatures are unusual, and 2013 adds to the evidence for ongoing climate change,” said GISS climatologist Gavin Schmidt. “While one year or one season can be affected by random weather events, this analysis shows the necessity for continued, long-term monitoring.”
Weather patterns and other natural cycles cause fluctuations in average temperatures from year to year. This is especially the case on regional and local levels. For instance, while the globe experienced notably warm temperatures in 2013, the continental United States had its 42nd warmest year, according to GISS analysis. On the other hand, 2013 was the hottest year in Australia’s recorded history.
Regardless of the regional differences in any year, continued increases in greenhouse gas levels in Earth’s atmosphere are driving a long-term rise in global temperatures. Each calendar year will not necessarily be warmer than the year before. But with the current level of greenhouse gas emissions, scientists expect each decade to be warmer than the previous one. The decade-by-decade temperature trend is depicted in the second map above and in the downloadable animations.
It has been 38 years since the recording of a year with cooler than average temperatures. The graph below shows how the long-term temperature trend has continued to rise even when El Niño and La Niña events skew temperatures warmer or colder in any one year. Orange bars represent global temperature anomalies in El Niño years, with the red line showing the longer trend. (The classification of years comes from the NOAA Oceanic Niño Index.) Blue bars depict La Niña years, with a blue line showing the trend. El Niño/La Niña neutral years are shown in gray, and the black line shows the overall temperature trend since 1950. Note that even the La Niña years are warmer than they used to be.
Scientific evidence says the level of carbon dioxide in Earth’s atmosphere presently is higher than at any time in the past 800,000 years. In 1880, the first year included in the GISS analysis, the global carbon dioxide level was about 285 parts per million; by 2013, it peaked at more than 400 parts per million. Carbon dioxide is a greenhouse gas that traps heat and plays a major role in controlling changes to Earth's climate. It occurs naturally and also is emitted by the burning of fossil fuels.
NASA images by Gavin Schmidt and Robert Simmon, based on data from the NASA Goddard Institute for Space Studies. Caption by Mike Carlowicz and Michael Cabbage.