Global Warming Metrics, New Sea Level Rise Projections

We're finally getting a handle on climate change impacts.   We've just learned that it takes roughly a million years for most species to evolve as needed to adapt to a 1C change in global temperatures.  That's not a good thing in a world that's expected to heat up 4C in the span of a single century.

Now we've got a metric for sea level rise thanks to the Potsdam Institute for Climate Impact Research.   In their assessment, one degree Celsius of warming will add 2.3 metres to sea level rise.

"Greenhouse gases emitted today will cause sea level to rise for centuries to come. Each degree of global warming is likely to raise sea level by more than 2 meters in the future, a study now published in the Proceedings of the National Academy of Sciences shows. While thermal expansion of the ocean and melting mountain glaciers are the most important factors causing sea-level change today, the Greenland and Antarctic ice sheets will be the dominant contributors within the next two millennia, according to the findings. Half of that rise might come from ice-loss in Antarctica which is currently contributing less than 10 percent to global sea-level rise." 

Did you get that?  The greenhouse gases we're emitting today will plague our descendants for centuries to come.  We're creating the gift that just keeps on giving at least for the next two millennia.

As for the rising damp, some places will get it much worse than others.  The U.S. eastern seaboard, for example, will face sea level rise three to four times the global average.   The U.S. Geological Survey puts this down to local conditions.

The report shows that the sea-level rise hotspot is consistent with the slowing of Atlantic Ocean circulation. Models show this change in circulation may be tied to changes in water temperature, salinity and density in the subpolar north Atlantic. 

"Many people mistakenly think that the rate of sea level rise is the same everywhere as glaciers and ice caps melt, increasing the volume of ocean water, but other effects can be as large or larger than the so-called 'eustatic' rise," said USGS Director Marcia McNutt. "As demonstrated in this study, regional oceanographic contributions must be taken into account in planning for what happens to coastal property."

Governments are naturally reticent when it comes to projections, preferring to work on best case scenarios.   That's true here in British Columbia where the provincial government is planning for sea level rise of 80 cms. in Nanaimo and 1.2 metres in the Lower Mainland.  Even with these optimistic projections, the B.C. government warns of a host of impacts, including

• More frequent and extreme high water levels in coastal areas
• Increased erosion and flooding
• Increased risk to coastal infrastructure, as well as increased maintenance and repair costs
• Loss of property due to erosion
• Loss of habitat and reduced biodiversity
• Saltwater intrusion into coastal aquifers
• Loss of cultural and historical sites

If the Potsdam Institute study is right, the B.C. government's projections could be unduly, perhaps even dangerously inaccurate.  The Lower Mainland, for example, is over-populated, far beyond the area's environmental carrying capacity.  59% of British Columbians live there and the population continues to expand rapidly.   Some communities, in Richmond for example, are already well below sea level and are experiencing subsidence.   Sinking ground levels, rising sea levels, not a good mix.