Daily Global Sea Ice Area and Trend

Context: the average global March ice area is about 16 million sq. km. On 13 March it was 0.0% (00/16 (million sq. km) above/below the 1979-2000 average for the date. This is well within normal variation. Not subject to urban heat island effects, the trend in global sea ice extent is a primary indicator of climate change, or the lack thereof.

(Source: Department of Atmospheric Sciences at the University of Illinois).
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Analysis: This is our primary indicator of warming or cooling, but it only goes back to 1979, when satellite sensors and analytical programs could get a handle on measuring the area covered by sea ice. Even today it has problems, such as dealing with water on ice, as happens after a warm spell. The sensor sees water, not ice, but this does not mean the underlying ice is gone. If the Arctic loses ice, but the global balance is about the same, there is no global warming.