Global mercury up by three quarters of a degree over last century

THE world has warmed by around 0.75C since the turn of the 20th century, scientists have said.

The calculation is based on updated records of global temperatures, which go back more than 160 years.

The new version of a temperature series dating back to 1850 by the Met Office Hadley Centre and the University of East Anglia relies on more data sourced from places such as Canada and Russia where the Arctic is warming more quickly than other areas.

More information from other parts of the world including Africa and Australia has also been added, with data from around an additional 500 stations in total to increase the coverage of land temperature records across the globe.

The effects of differences in the way sea surface temperature measurements have been made in the past, for example water temperatures taken from buckets hauled on board ship or made from engine rooms of ships, have also been addressed.

Colin Morice, climate monitoring research scientist at the Met Office, said: “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.

“These have been combined to give us a clearer a picture of what the historical record can tell us about global climate change over the past 161 years.

“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 0.75C 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.

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.

Slight increases in the temperatures for recent years is due to inclusion of more data from the rapidly-warming Arctic.

Professor Phil Jones, director of CRU, said the temperature series may not have been fully capturing changes in the Arctic because of a lack of data from the area.

“For the latest version we have included observations from more than 400 stations across the Arctic, Russia and Canada. This has led to better representation of what’s going on in the large geographical region.”

Previous analysis of temperature records came under fire at the height of the “climategate” scandal, in which researchers were wrongly accused by sceptics of manipulating data to support a theory of global warming.

Scientists were criticised for not publishing the data behind the temperatures series, and today Prof Jones said virtually all the data for the records underpinning the latest analysis would be publicly available.