Warming Trends in the Arctic from Clear Sky Satellite Observations

Abstract

Satellite thermal infrared data on surface temperatures provide pan-Arctic coverage from 1981 to 2001 during cloud-free conditions and reveal large warming anomalies in the 1990s compared to the 1980s and regional variability in the trend. The rms error of the derived surface temperatures when compared with in situ data ranges from 1.5 to 3 K over the 20-yr period. Average temperature trends are generally positive at 0.33 ± 0.16°C decade⁻¹ over sea ice, 0.50 ± 0.22°C decade⁻¹ over Eurasia, and 1.06 ± 0.22°C decade⁻¹ over North America. The trend is slightly negative and insignificant at −0.09 ± 0.25°C decade⁻¹ in Greenland with the negatives mainly at high elevations. The trends are also predominantly positive in spring, summer, and autumn causing the lengthening of the melt season by 10–17 days per decade while they are generally negative in winter. The longer-term in situ surface temperature data shows that the 20-yr trend is 8 times larger than the 100-yr trend suggesting a rapid acceleration in the warming that may be associated with the recent change in phase of the Arctic Oscillation that has been linked to increasing greenhouse gases in the atmosphere.