Guest post by David Middleton
Sea levels could rise far more rapidly than expected in coming decades, according to new research that reveals Antarctica’s vast ice cap is less stable than previously thought.
The UN’s climate science body had predicted up to a metre of sea level rise this century – but it did not anticipate any significant contribution from Antarctica, where increasing snowfall was expected to keep the ice sheet in balance.
According a study, published in the journal Nature, collapsing Antarctic ice sheets are expected to double sea-level rise to two metres by 2100, if carbon emissions are not cut.
Previously, only the passive melting of Antarctic ice by warmer air and seawater was considered but the new work added active processes, such as the disintegration of huge ice cliffs.
“This [doubling] could spell disaster for many low-lying cities,” said Prof Robert DeConto, at the University of Massachusetts Amherst, who led the work. He said that if global warming was not halted, the rate of sea-level rise would change from millimetres per year to centimetres a year. “At that point it becomes about retreat [from cities], not engineering of defences.”
I don’t know if Mr. Carrington has poor math, poor reading skills or is just inclined to hype his stories. The “study, published in the journal Nature,” is actually an interesting paper and the full text is available for reading, but not downloading. The authors devised a model which couples Antarctic ice loss to past sea level rises in the Pliocene and Pleistocene. They then used this model, coupled with “Representative Carbon Pathway (RCP)” scenarios to forecast future sea level rises.
DeConto and Pollard conclude that “Antarctica has the potential to contribute more than a metre of sea-level rise by 2100.”
Mr. Carrington apparently added this 1 meter to the IPCC’s 1 meter to come up with 2 meters. He even bastardized a quote from Dr. DeConto…
“This [doubling] could spell disaster for many low-lying cities.”
The word “doubling” is Carrington’s, not DeConto’s.
I don’t know if Mr. Carrington read the paper or not; however the authors never forecasted a sea level rise of 2 meters by 2100…
The IPCC sea level forecast for 2100 in RCP 8.5 with ice-sheet rapid dynamics is 0.74 m (0.52 to 0.98 m), not 1 meter. The Antarctic contribution is 0.04 m (-0.06 to 0.12).
If we go with the most likely, worst case RCP 8.5 scenarios…
IPCC – Antarctica = 0.70 m
DP 2016 Antarctica = 1.05 m
Sum =1.75 m
Under this scenario, the Antarctic contribution would actually more than double the IPCC’s forecast… But it would still be less than 2 m.
Now, let’s have a look at RCP 8.5…
This noachian deluge forecast is based on the assumption that the atmospheric CO2 concentration will rise to 1,120 ppm by 2100
Does anyone actually believe that humans could burn enough stuff over the next 84 years to drive CO2 levels up by 700 ppm above the current ~400 ppm? CO2 would have to rise by an average of 8.33 ppm per year over the remainder of the 21st century.
It appears that RCP 8.5 will turn Earth into Venus by 2100 AD.
But, what happens if I use real data?
Let’s assume that the atmospheric CO2 level will rise along an exponential trend line until 2100.
I get a CO2 level of 560 ppmv, in line with RCP 4.5… which leads to 0.53 (± 0.18) meters of sea level rise by 2100.
The only way sea level rise could approach the high end of the IPCC range is if it exponentially accelerates…
The rate from 2081-2100 would have to average 20 mm per year, twice that of the Holocene Transgression. This is only possible in bad science fiction movies in which Earth turns into Venus by 2100.
There simply is no data- or observation-driven reason to conclude that sea level will rise by more than 0.16 to 0.28 m (7-11 inches) during the 21st century under a realistic “business as usual” Representative Carbon Pathway.
RCP 8.5 is even more batschist crazy then I had assumed…