However one interprets the science, it’s bad news
The recent IPCC report estimates that sea level rise will be 0.3 meters by the end of this century. However more recent evidence of acceleration indicates that 0.5 meters may be reached if all other variables remain the same.
These estimates are likely to be conservative for several reasons. Firstly the IPCC collection of data for the 4th IPCC report finished about two years ago. Data since then suggests acceleration. Secondly, the IPCC scientists are conservative in their consensus opinions. Like many scientists they are reticent to overstate even if they feel there is a likelihood of more extreme rises. Thirdly, the IPCC final reports have government influence to tone down the reports – governments do not want to face the facts on this issue.
There is now concern that the models used in data reviewed by the IPPC underestimate some global warming impacts. A vital brake on warming, the uptake of CO2 by oceans, appears not to be working as efficiently as had been thought and sea ice is melting and sea level is rising faster than predicted.
The oceans of the world function to remove carbon dioxide from the atmosphere. Previous measurements of ocean uptake may have been overestimated. A paper in Science on-Line in May indicates that the oceans are taking up 5 to 30% less carbon dioxide than predicted. Previous models did not account for increased winds that push currents to bring deep carbon to the surface where it percolates back into the atmosphere.
In January sea-level-rise predictions were published by Rahmstorf in Science.
The actual rise tracked the uppermost limits of 2001 IPCC projections. Despite the previous underestimate, this year’s IPCC report gave even smaller sea-level-rise projections, partly because authors omitted any estimate of accelerating ice flow.
Scientists have assumed that polar ice sheets were in balance for lack of better information. In 2001, the IPCC said that loss of ice sheets, leading to faster sea level rise, was “very unlikely during the 21st century.” The latest IPCC report abandons that position, concluding that the Antarctic ice sheet is already contributing to sea level rise. However recent satellite imaging of ice sheets is very concerning. In a recent paper in Environmental Research Letters entitled “Scientific reticence and sea level rise”,J E Hansen of NASA reviews this data. He concludes “The broader picture gives a strong indication that ice sheets will, and are already beginning to, respond in a nonlinear fashion to global warming. There is enough information now, in my opinion, to make it a near certainty that IPCC BAU (business as usual) climate forcing scenarios would lead to a disastrous multi-meter sea level rise on the century timescale.” Hansen’s estimates of possible sea level rise based on Antarctic ice sheet disintegration now include the possibility of a 5 meter rise. Hansen is a well respected scientist and his views must be taken seriously.
The political message.
We need to move into a new paradigm. One has to ask what will be the sea level rise by the time there is an efficient, effective carbon trading scheme. In times of national emergency, do nations leave solutions to the market? In England in the 39-45 war, citizens awoke one morning to find that all the metal fences in the street had gone! Churchill directed that they go to munitions. No waiting for market forces then. Planes and tanks were needed immediately.
David Shearman