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Version 0 Version 1
Update for world temperature data Update for world temperature data
(about 1 hour later)
By Mark Kinver Environment reporter, BBC NewsBy Mark Kinver Environment reporter, BBC News
Researchers have updated HadCRUT - one of the main global temperate records, which dates back to 1850.Researchers have updated HadCRUT - one of the main global temperate records, which dates back to 1850.
One of the main changes is the inclusion of more data from the Arctic region, which has experienced one of the greatest levels of warming.One of the main changes is the inclusion of more data from the Arctic region, which has experienced one of the greatest levels of warming.
Another change is the way sea surface temperature (SST) is recorded, accounting for technological advances now available to researchers.Another change is the way sea surface temperature (SST) is recorded, accounting for technological advances now available to researchers.
The update is reported in the published in the Journal of Geophysical Research.The update is reported in the published in the Journal of Geophysical Research.
Despite the revisions, the overall warming signal has not changed. The scientists say it has remained at about 0.75C (1.4F) since 1900.Despite the revisions, the overall warming signal has not changed. The scientists say it has remained at about 0.75C (1.4F) since 1900.
However, the amendments have resulted in a change in the dataset's "warmest year on record".However, the amendments have resulted in a change in the dataset's "warmest year on record".
Previously, it was 1998. However, the revised data now lists 2010 as the warmest, with 1998 recorded as the third warmest.Previously, it was 1998. However, the revised data now lists 2010 as the warmest, with 1998 recorded as the third warmest.
Fuller pictureFuller picture
The dataset, compiled by the UK Met Office's Hadley Centre and the Climatic Research Unit (Cru) at the University of East Anglia, is one of three global records used extensively by climatologists.The dataset, compiled by the UK Met Office's Hadley Centre and the Climatic Research Unit (Cru) at the University of East Anglia, is one of three global records used extensively by climatologists.
The other two are produced by US-based researchers at Nasa and the National Oceanic and Atmospheric Administration (Noaa).The other two are produced by US-based researchers at Nasa and the National Oceanic and Atmospheric Administration (Noaa).
Cru's director, Phil Jones, explained why it was necessary to revise the data.Cru's director, Phil Jones, explained why it was necessary to revise the data.
"HadCRUT is underpinned by observations and we've previously been clear it may not be fully capturing changes in the Arctic because we have had so little data from the area," he said."HadCRUT is underpinned by observations and we've previously been clear it may not be fully capturing changes in the Arctic because we have had so little data from the area," he said.
"For the latest version, we have included observations from more than 400 (observation) stations across the Arctic, Russia and Canada.""For the latest version, we have included observations from more than 400 (observation) stations across the Arctic, Russia and Canada."
Prof Jones added: "This has led to better representation of what's going on in the large geographical region."Prof Jones added: "This has led to better representation of what's going on in the large geographical region."
Temperature records show that the planet's northern latitudes are warming at a faster rate than the rest of the planet, so climate scientists are keen to monitor this region more closely.Temperature records show that the planet's northern latitudes are warming at a faster rate than the rest of the planet, so climate scientists are keen to monitor this region more closely.
Kicking the bucketKicking the bucket
With advances in technology in recent years, ships now have electronic sensors that can accurately record sea surface temperature.With advances in technology in recent years, ships now have electronic sensors that can accurately record sea surface temperature.
This development has highlighted a systematic anomaly in traditional methods of collating the data in the past.This development has highlighted a systematic anomaly in traditional methods of collating the data in the past.
This included variations in the buckets used to collect sea water, and where the temperature was recorded.This included variations in the buckets used to collect sea water, and where the temperature was recorded.
Improvements in the way SST was collected allowed scientists to recalculate data, making amendments to the data collected in previous years.
"An example of this is the rapid change in the kinds of measurements we see in the digital archives around the Second World War," explained Peter Stott, head of climate monitoring and attribution at the Met Office."An example of this is the rapid change in the kinds of measurements we see in the digital archives around the Second World War," explained Peter Stott, head of climate monitoring and attribution at the Met Office.
"Research has shown readings from buckets were generally cooler so when the database changes from one source to another, you see artifical jumps in the temperature."Research has shown readings from buckets were generally cooler so when the database changes from one source to another, you see artifical jumps in the temperature.
"We have quantified these effects and corrected them, providing a clearer view of the evolution of global temperatures.""We have quantified these effects and corrected them, providing a clearer view of the evolution of global temperatures."