Most of the projections in the science portion of the IPCC’s 2007 4th Assessment Report have been shown many times since its issuance to be too conservative. Temperatures have risen faster; ice (sea- and land-based) has melted faster; ocean acidification and warming has happened faster, the number of extreme weather events has increased faster, etc.
I’ve written before about most of these. I will take this space to write once again about polar ice melting faster than projected (according to observations) and the impact that will have on global coastlines.
According to the executive summary of a new assessment of Arctic climate, the international Arctic Monitoring and Assessment Program (AMAP) reports that Arctic temperatures in the past six years were higher than at any time since measurements began in 1880. Moreover, feedback mechanisms have already started.
What this means is the arctic sea ice area and global sea level projections made by the IPCC just 4 years ago underestimate this year’s conditions, which means they also very likely underestimate future conditions too. In an updated projection that has deep significance for billions of people worldwide:
The melting of Arctic glaciers and ice caps, including Greenland’s massive ice sheet, are projected to help raise global sea levels by 35 to 63 inches (90-160 centimeters) by 2100, AMAP said, though it noted that the estimate was highly uncertain.
That’s up from a 2007 projection of 7 to 23 inches (19-59 centimeters) by the U.N. panel, which didn’t consider the dynamics of ice caps in the Arctic and Antarctica.
Is the difference between one-half to 2 feet and 3 feet to 5 feet significant? Only those of us who are sane seem to think so. This is but one effect of oil corporations continuing to post record profits quarter after quarter, year after year. How much infrastructure exists near 5ft above sea level worldwide? How much is that infrastructure worth? How much cropland exists at those low altitudes? How many miles of ruined cropland from rising seas only will occur before widespread food shortages occur? How much is our lifestyles worth; how much do they really cost?
AMAP scientists will discuss their findings in Copenhagen, Denmark starting tomorrow.
My most recent `State of the Poles` post discussed shorter-term influences on sea ice conditions (monthly to seasonal effects). I’ve stated in that series that a new regime now exists for the Arctic. Findings like these support that assessment.
For the hard-core curious, the key findings of the report are reprinted below the fold (h/t ClimateProgress)