November 29th, 2012 by James Ayre
Global sea levels are rising much faster than previously estimated by the Intergovernmental Panel on Climate Change’s (IPCC), new research has shown. 60 percent faster to be exact, if such a rate was to continue, or even increase as is likely, sea level rise could be very significant by the end of the century, and have important consequences for humans.
The IPCC’s previous ‘best estimate’ was for 2mm a year, the actual rate now is 3.2 mm a year.
The new research was done by the Potsdam Institute for Climate Impact Research, Tempo Analytics and Laboratoire d’Etudes en Géophysique et Océanographie Spatiales. The researchers note that it’s important to keep track of how accurate past projections have turned out to be, as they generally seem to underestimate the speed of change. It’s especially important now, as the projections made by the IPCC are commonly bring used in governmental decision making.
The study was done by doing an analysis “of global temperatures and sea-level data over the past two decades, comparing them both to projections made in the IPCC’s third and fourth assessment reports. Results were obtained by taking averages from the five available global land and ocean temperature series.”
“After removing the three known phenomena that cause short-term variability in global temperatures — solar variations, volcanic aerosols and El Nino/Southern Oscillation — the researchers found that the overall warming trend at the moment is 0.16°C per decade, which closely follows the IPCC’s projections.”
The satellite measurements that were taken of sea levels though, show a considerably faster rate of sea level rise than what was projected. At least sixty percent quicker than the IPCC’s AR4 projections.
“Satellites measure sea-level rise by bouncing radar waves back off the sea surface and are much more accurate than tide gauges as they have near-global coverage; tide gauges only sample along the coast. Tide gauges also include variability that has nothing to do with changes in global sea level, but rather with how the water moves around in the oceans, such as under the influence of wind.”
The study also clarifies that it’s very unlikely that the faster than predicted rate is because of ‘natural’ internal variability in the climate system.
The lead author of the research, Stefan Rahmstorf, said: “This study shows once again that the IPCC is far from alarmist, but in fact has under-estimated the problem of climate change. That applies not just for sea-level rise, but also to extreme events and the Arctic sea-ice loss.”
The research was just published November 28th, in IOP Publishing’s journal Environmental Research Letters.
Source and Image: Institute of Physics
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