A new study has found that the lowest layer of the Earth's atmosphere has been gradually warming up over the past 25 years, putting to rest past discrepancies and reaffirming that global warming occurred during the late 20th century.
Previous analysis of satellite measurements taken between 1978 and 2002 found no significant change in the temperature of the troposphere, which extends eight to 11 kilometres above the Earth. This contradicted temperature increases observed at ground level, as well as the predictions of climate models.
But research by US scientists has now questioned this finding – which has been used by some researchers and policy makers to cast doubts on global warming. By combining the satellite data with a temperature model that accounts for daily and seasonal cycles, they have found that the troposphere is warming up by about 0.024°C every year.
Writing in this week's Science Express the authors say that their approach is "radically different" from previous methods used to assess troposphere warming. And they note that their results are in line with the warming recorded on the Earth's surface.
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