A global warming hiatus many researchers believe has been happening since the turn of the millennium has not been taking place after all, according to a new report from NASA. New data and improved analysis methods show that rising temperatures have increased around the world over the last decade and a half.
The Intergovernmental Panel on Climate Change (IPCC) stated in 2013 that the rise of surface temperatures around the globe between 1998 and 2012 was less than half of that seen in the period stretching from 1951 and 2012.
Just one year later, in 2014, NASA declared the planet had experienced its warmest year since 1880. Adding the last two years of data to meteorological records, combined with improved data analysis techniques, largely eliminated the supposed pause in rising global temperatures.
"Our new analysis suggests that the apparent hiatus may have been largely the result of limitations in past datasets, and that the rate of warming over the first 15 years of this century has, in fact, been as fast or faster than that seen over the last half of the 20th century," said Thomas Karl, director of the National Centers for Environmental Information.
Many critics of the idea that human beings are responsible for worldwide climate change cite a lack of rising temperatures since the year 2000 as evidence against global warming.
Environmentalists had questioned where additional heat may have been stored. Some researchers carried out studies and ran models suggesting oceans may be acting as heat sinks, temporarily delaying the rise in global temperatures.
Ocean temperatures were measured primarily by researchers aboard ships before the 1970s, but since that time, buoys have become the more common method for collecting this data. Researchers for NOAA showed that buoys record cooler temperatures overall than those collected by investigators using ships. Information regarding how individual voyages collected data on missions to record ocean temperatures was also taken into account in the new study in an effort to further refine corrections in the reported data. Analysis showed that an incomplete record of ocean temperatures may have led to an erroneous conclusion regarding global warming.
Short-term changes, such as those caused by El Niño and La Niña, can still affect ocean temperatures over the course of years. The long-term trends are of particular concern to climatologists. Researchers are stressing that this finding does not refute the ability of scientific models.
"The notion that there was a slowdown in global warming, or a hiatus, was based on the best information we had available at the time," Karl said.
Analysis of the global warming hiatus was published in the journal Science.
