Greenland Ice Varies, Don’t Panic

The scare du jour is about Greenland Ice Sheet (GIS) and how it will melt out and flood us all.  It’s declared that GIS has passed its tipping point, and we are doomed.  Typical is the Phys.org hysteria: Sea level rise quickens as Greenland ice sheet sheds record amount:  “Greenland’s massive ice sheet saw a record net loss of 532 billion tonnes last year, raising red flags about accelerating sea level rise, according to new findings.”

Panic is warranted only if you treat this as proof of an alarmist narrative and ignore the facts and context in which natural variation occurs. For starters, consider the last four years of GIS fluctuations reported by DMI and summarized in the eight graphs above.  Note the noisy blue lines showing how the surface mass balance (SMB) changes its daily weight by 8 or 10 gigatonnes around the baseline mean from 1981 to 2010.  Note also the summer decrease between May and August each year before recovering to match or exceed the mean.

The other four graphs show the accumulation of SMB for each of the last four years including 2020.  Tipping Point?  Note that in both 2017 and 2018, SMB ended about 500 Gt higher than the year began, and way higher than 2012, which added nothing.  Then came 2019 dropping below the mean, but still above 2012, and finally this year matching the 30-year average.  Note also that the charts do not integrate from previous years; i.e. each year starts at zero and shows the accumulation only for that year.  Thus the gains from 2017 and 2018 do not result in 2019 starting the year 1000 Gt, but at zero.

via Science Matters

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August 21, 2020 at 09:21AM

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