Get your sea level rise facts straight
Re: “When talking sea level, not all facts appear to be equal”, (Citizen, March 1)
John Walker’s letter of March 1 commenting on Bellerive’s letter of Feb. 20 contains several misconceptions. Walker claims that melting of polar ice does not contribute to sea level rise because it is already on the ocean. He misses the simple fact that most ice in the Arctic is land-based on the Greenland ice sheet, about 2-3 km thick, where sea ice thickness is measured in metres. He further claims that sea level measurements are inaccurate. However, very accurate measures of ice melt and sea level are carried out today using satellite altimetry (from ICESat) and gravimetric data (from GRACE satellite).
When climate science refers to polar ice melt and sea level rise, they refer to melting of land-based ice, on either Greenland, Antarctica, or alpine glaciers on mountains. Those, Mr. Walker, certainly DO contribute to sea level rise. The Greenland ice sheet is now melting three to four times faster than was believed in the 1990s. If all this ice melted, sea level would rise by seven metres all around the globe. We cannot now avoid 2 C global warming in this century, given inaction by governments and industry, and the very best estimates are that sea level will rise more than two metres for every 1 C rise in global temperature, meaning a minimum further rise of two metres. Add to that the result of thermal expansion of the oceans, since much of the heat added to the atmosphere ultimately ends up there.
Sea level rise is only one part of the equation, since ocean surges during storms mean that anything less than five metres above sea level is at risk from catastrophic flooding. Mr. Bellerive was quite correct in pointing out the risks in Cowichan Bay.
Mr. Walker, if you are going to use science, get your facts straight.