Tuesday, August 25, 2009

GLOBAL WARMING: Sea Level Rise to Be Higher & Faster Than Predicted by IPCC

By Paul Andrew Roth

Recent research suggests that global warming-related sea level rise will be faster and greater than previously forecast. The poles are experiencing disproportionate warming and are undergoing accelerated melting. The amount of this melt will largely determine the degree of sea-level rise over coming centuries.

Melting is proceeding at an unprecedented pace that already exceeds the worst-case scenario in the 2007 IPCC report, and there is a growing scientific consensus that the IPCC wildly underestimated the rapidity and extent of glacial melting.

Over the coming centuries anthropogenic warming will be the main driver of sea-level rise, even if emissions decreased and atmospheric levels of CO2 stabilised at 450ppm. If we burn all remaining fossil fuel stores then sea level will be over 10 metres higher than it is today.

While the single biggest contributor to sea-level rise during the twentieth century was the melting of non-polar glaciers (such as those in the Himalayas and Andes), polar ice is predicted to rapidly overtake it. Thermal expansion of the oceans will also play a role but will pale into insignificance compared to the amount of water currently locked up in Greenland and Antarctica (which will raise sea level by 70 metres if it all melts).

There are three main mechanisms contributing to the accelerating loss of polar ice.

Glacial lubrication by meltwater (where melting freshwater infiltrates through cracks in the glacier, reaching the bedrock and acting as a lubricant that accelerates glacial flow) is one mechanism. Initially thought to be the most important mechanism, it is probably not the primary factor that will lead to accelerated sea level rise.

A second mechanism is the break-up of floating ice shelves (like the Antarctic's Larsen B shelf). While not increasing sea level directly (because they are already floating), they appear to act as a "cork" for the glacier behind them. Once they disappear, glacial flow accelerates significantly - This was observed at Larsen B where immediate glacial acceleration (of eight times normal speed) followed its demise.

The third (and probably most important) mechanism of ice loss has only just been discovered - the melting of Antarctic ice by the upwelling of warmer water from several hundred metres below the surface of the sea. This is occurring in increasingly greater amounts due to global warming. A warming pole has changed the pattern of wind flow around Antarctica, in turn changing sea currents and directing warm water towards vulnerable ice shelves.

This process is already happening to some ice shelves (notably the ice shelf holding back the massive Pine Island glacier) and could cause a sea-level rise of 3.3 metres over the next few hundred years.

Summary: Ice at the poles is melting much faster than predicted, and the majority of sea level experts are expecting at least a metre of sea-level rise by 2100.

Paul Roth is a health professional concerned about human-caused global warming and climate change. He is the founder of Climate Change Health, a blog dedicated to documenting climate change and its effects on human health.

Article Source: http://EzineArticles.com/?expert=Paul_Andrew_Roth

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