The UK Met Office and University of East Anglia's Climatic Research Unit has updated HadCRUT, one of, if not the most comprehensive, accurate and widely used global temperature data sets in the world.
Providing a basis for a global temperature record dating back to 1850, HadCRUT version 4 includes newly available data, "notably adding much more information from "the sparsely observed northern higher latitude region." Differences and peculiarities in the way measurements of sea surface temperature were also taken into account, and the new version also provides much greater detail regarding the uncertainty of statistical results, according to a Met Office press release.
Commenting on the release of HadCRUT4,
"The new study brings together our latest and most comprehensive databases of land and marine temperature observations, along with recent advances in our understanding of how measurements were made at sea," Met Office Climate Monitoring Research Scientist Colin Morice said. "These have been combined to give us a clearer picture of what the historical data can tell us about global climate change over the past 161 years."
Global Warming Signal Persists
While the revised and augmented data resulted in changes to average global temperatures of individual years, they didn't change the overall global warming signal, Morice elaborated. "Updates have resulted in some changes to individual years in the nominal global mean temperature record, but have not changed the overall warming signal of about 0.75 °C since 1900."
"The latest study suggests that 2010 and 2005 were the warmest years on record, slightly warmer than 1998 - which the Met Office and UEA’s Climatic Research Unit (CRU) had previously put as the hottest year," according to a report from The Scotsman. "But the margin of error in the results means the years were all similarly warmer than average global temperatures. All of the ten warmest years in the record occurred in the past 14 years."
Incorporating much more data from the Arctic, which has been warming faster than other areas of the world, has been a focal point for HarCRUT 4's science team. Doing so resulted in slight changes to HadCRUT 4's mean temperatures, particularly in the data set's later years.
"For the latest version we have included observations from more than 400 stations across the Arctic, Russia and Canada," explained Phil Jones, director of the Univ. of East Anglia's Climatic Research Unit. "This has led to better representation of what's going on in the large geographical region."
Taking better account of differences in the way sea surface temperatures were observed and measured also resulted in changes to individual years further back in the data set, particularly the mid-20th century. "An example of this is the rapid changes in the kinds of measurements we see in the digital archives around the Second World War," the Met Office's head of Climate Monitoring and Attribution commented.
"Some sea surface temperature observations were taken from buckets hauled on board ships and others were made in the engine rooms. Research has shown readings from buckets were generally cooler so when the database changes from one source to another you see artificial jumps in the raw data. We've quantified these effects and corrected for them providing a clearer view of the evolution of global temperatures."
*Image credit: Met Office Founder Capt. Robert FitzRoy; Courtesy: UK Met Office