Sea Level Rise Best Case Scenario: 50cm Rise, 10% of World Population Hit

Islands such as the Maldives (pictured here), as well as the world's highly populated delta regions in India, Southeast Asia, and China will be seriously threatened by rising sea levels. Photo: Moosa Ali via flickr

Think sea level rise caused by global climate change won't be a big deal? Probably not if you're a regular TreeHugger reader. But there have been some variations in predictions of just how much land will become inundated and how many people will be climate refugees, so I won't blame you if you're not entirely clear on the matter. Well, at the Copenhagen Climate Congress scientists have clarified some of the predictions made in the 2007 IPCC report regarding rising seas:Half a Meter The Minimum That Will Occur, One Meter or More Possible by 2100
Research presented today shows that by 2100 sea level rise could be one meter or more at the upper end of the spectrum (assuming we don't reduce carbon emissions quickly to hold temperature rise to 2°C). At the lower end of the spectrum it looks unlikely that sea level rise will be less than half a meter.

Uncertainty Over Ice Sheet Melt Kept IPPC Report Projections Low
In the 2007 IPCC report sea level rise was projected to be in the range of 18-59cm. However, not all factors were included in these projections (most notably uncertainty surround how ice sheets would react to rising temperatures and interact with oceans) and are consequently too low.

Eric Rignot, Professor of Earth System Science at the University of California Irvine and Senior Research Scientist at NASA's Jet Propulsion Lab:

The numbers from the last IPCC are a lower bound because it was recognized at the time that there was a lot of uncertainty about ice sheets. The numerical models used at the time did not have a complete representation of outlet glaciers and their interactions with the ocean. The results gathered in the last 2-3 years show that these are fundamental aspects that cannot be overlooked. As a result of the acceleration of outlet glaciers over large regions, the ice sheets in Greenland and Antarctica are already contributing more and faster to sea level rise than anticipated. If this trend continues, we are likely to witness sea level rise one meter or more by year 2100.

Several Meters Sea Level Rise Possible in Coming Centuries
John Church from the Centre for Australian Weather and Climate Research added,
Unless we undertake urgent and significant mitigations, the climate could cross a threshold during the 21st century committing the world to a sea level rise of meters.

Those multiple meters Church is referring to would be in the years past 2100, by the way. If mitigation efforts are not sufficient sea level rise would continue in the 22nd and 23rd centuries. According to one chart shown, possibly as much a 5 meters in the next two centuries.

No matter the exact amount of sea level rise, the message presented is loud and clear: Even at the lowest levels of project sea level rise in the 21st century mean that 10% of the world's current population will be hit by rising seas.

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