German skeptic site Die Kalte Sonne here debunks a recent alarmist article appearing in Spiegel aimed at shocking its readers. The reality, it turns out, is not shocking at all.
Greenland ice doomed?
According to Spiegel, the Greenland ice sheet is already doomed (that is unless we skip the usual democratic process and just act immediately).
Spiegel claims Greenland “glaciers are continuously losing huge masses of ice” and that the system there is “dramatically off balance”. The leftist Hamburg-based weekly reported:
The melting of the glaciers on Greenland has apparently passed the point of no return. Even if the global rise in temperature were to stop immediately, the ice sheet would continue to retreat, report researchers led by Michalea King of Ohio State University report in the journal “Communications Earth and Environment“.
Read more at Spiegel
4°C warmer 11,000 years ago
But Die kalte Sonne wondered if this were really so, and needed only 2 mouse clicks to find a recent temperature reconstruction for Greenland’s past (Lecavalier et al. 2017, pdf here). The paper’s Figure 4a shows the temperatures, with the temperature of 1950 at the far right which in paleo-climatology is always meant as “present”.
Thus, 11,000 years ago, it was up to 4°C warmer than in 1950 over long periods of thousands of years, and today the warming has been about 1°C since then. Since we can see an ice sheet of 2,850,000 km³ (that is roughly Gt) today, the “point of no return” cannot have been exceeded 10,000 years ago. How does the heading then come about? We take a look at the associated work by King et al. 2020:
Dynamic ice loss from the Greenland Ice Sheet driven by sustained glacier retreat
The Greenland Ice Sheet is losing mass at accelerated rates in the 21st century, making it the largest single contributor to rising sea levels. Faster flow of outlet glaciers has substantially contributed to this loss, with the cause of speedup, and potential for future change, uncertain. Here we combine more than three decades of remotely sensed observational products of outlet glacier velocity, elevation, and front position changes over the full ice sheet. We compare decadal variability in discharge and calving front position and find that increased glacier discharge was due almost entirely to the retreat of glacier fronts, rather than inland ice sheet processes, with a remarkably consistent speedup of 4–5% per km of retreat across the ice sheet. We show that widespread retreat between 2000 and 2005 resulted in a step-increase in discharge and a switch to a new dynamic state of sustained mass loss that would persist even under a decline in surface melt.
Is there any talk of an irreversible end of the Greenland ice sheet? From the abstract:
We show that widespread retreat between 2000 and 2005 resulted in a step-increase in discharge and a switch to a new dynamic state of sustained mass loss that would persist even under a decline in surface melt.“
The authors see an acceleration in melting towards the ocean in the period 2000-2005, with not enough snowfall to compensate for the losses. They find a loss of about 500 Gt/year.
Only 0.15% of total ice mass
Unfortunately, they do not address the highly accurate gravity measurements with satellites in their paper. These data show a linear mass loss of only 275 Gt/year between 2003 and 2019 (with a gap in 2017 and 2018 due to a satellite change), so that in 17 years about 4200 Gt were lost, which is 0.15% of the total sheet.
What exactly do they say about the future?
Ultimately, predictions of future change will require improved understanding of the ice/ocean boundary and controls on glacier calving.“
Low-fact propaganda
This is much more cautious than what is being served up to us as “doomed” with the usual “overconfidence”. A look into the past is enough to unmask the media scream for what it is: low-fact propaganda.
Also read here at Ice Age Now.
