IN LATE 2015, a chilling report by scientists for
the International Cryosphere Climate Initiative
“Thresholds and closing windows: Risks of irreversible cryosphere climate change”
Warned that the Paris commitments will not prevent the Earth
“crossing into the zone of irreversible thresholds”
“result in processes that cannot be halted unless temperatures return to levels below pre-industrial”
The report says it is not well understood outside the scientific community that cryosphere dynamics are slow to manifest but once triggered “inevitably forces the Earth’s climate system into a new state, one that most scientists believe has not existed for 35–50 million years”
“It’s generally accepted that it’s no longer a question of whether the West Antarctic Ice Sheet will melt, it’s a question of when.
This kind of rifting (cracking) behaviour provides another mechanism for rapid retreat of these glaciers, adding to the probability that we may see significant collapse of West Antarctica in our lifetimes.”
The scientists I have communicated with take the view that Rignot, Mouginot et al. is a credible paper and, together with the evidence published since, it would be prudent to accept that WAIS has very likely passed its tipping point for mass deglaciation, with big consequences for global sea level rise (SLR).
DeConto and Pollard project more than a metre of SLR from Antarctica this century.
This tallies with the Hanse, Sato et al scenario, which is also consistent with the findings of Phipps, Fogwill and Turney.
The reality of multi-metre SLRs is not if, but how soon.
“The natural state of the Earth with present CO2 levels is one with sea levels about 70 feet (21 metres) higher than now”
says Prof. Kenneth G. Miller.
Other research scientists agree it is likely to be more than 20 metres over the longer term.
So how much could we expect sea levels to rise this century?
OVER TWO METRES
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