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Tuesday, December 23, 2008

AGU 2008: Evidence that Antarctica has warmed significantly over past 50 years

AGU 2008: Evidence that Antarctica has warmed significantly over past 50 years

New research presented at the AGU today suggests that the entire Antarctic continent may have warmed significantly over the past 50 years. The study, led by Eric Steig of the University of Washington in Seattle and soon to be published in Nature, calls into question existing lines of evidence that show the region has mostly cooled over the past half-century.

Steig and colleagues combined satellite thermal infra-red collected over 25 years with weather station data for the region. Although the satellite data span a shorter time period and are accurate only for blue sky days, i.e., when there is no cloud cover, they provide high spatial coverage of the region, which cannot be obtained from discrete ground measurements. In contrast, the weather station data provide complete temporal resolution over the past half-century.

Using an iterative process to analyse the data, they found warming over the entire Antarctic continent for the period 1957-2006. Restricting their analysis to 1969 to 2000, a period for which other studies have found a net cooling trend, Steig’s study found slight cooling in east Antarctica, but net warming over west Antarctica.

As well as uncovering evidence of warming over a wider region than previous studies have shown, the researchers found that warming occurred throughout all of the year and was greatest in winter and spring. In contrast, cooling over east Antarctica was restricted to autumn.

They independently confirmed these trends by using data from automatic weather stations, and excluding the satellite data.

Overall, the study suggests that warming is not limited to the Antarctica peninsula region. Steig says their findings are backed up by recent results from David Bromwich of the Byrd Polar Research Centre at Ohio State University also presented at this meeting and by a climate modelling study using data assimilation from Hugues Goosse of the Université Catholique de Louvain in Belgium and colleagues, which is due to be published in the journal Climate Dynamics.

The authors speculate that the warming trend may be due to shifts in circulation coupled with sea ice changes.

Olive Heffernan

Link to Nature blog post:

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