Oct. 18, 2009 -- This article is the first part of a three-part series, which considers the effect of global warming on ocean level rise, and examines life with constantly advancing seas from two perspectives: that of the landlubber and that of the seafarer.
In September 2009 the latest global temperature rise projections released by the Hadley Centre, part of the British Meteorological Office indicated an average rise of 4 degrees Celsius (that’s a balmy 7.2°F) by 2055 given a business as usual scenario. Some places will be a bit more stable, but the places that particularly matter – the ice caps, the methane-rich permafrosts in northern Canada and Siberia, and the Amazon rainforest – will be melting, off-gassing, and burning, respectively. The report offers some detail on what that would feel like:
And what of that lodestone, global sea level? This happens to be a very interesting question, because ocean levels are set to rise dramatically. According to UCLA scientists, the last time carbon dioxide levels were as high as they are today was 15 million years ago. At that time, the sea level was between 20 and 36 metres higher (75 to 120 feet), there was no permanent ice cap in the arctic, and very little ice in Antarctica or Greenland. That is where we are headed. The only remaining question is, How long will it take us to get there?
The authors of the Hadley Centre report predict a rise of just 1.4 metres by 2100. The IPCC in their 2007 4th Assessment Report predicted something like half a metre by 2100 based on a combination of the fattening of the oceanic envelope caused by thermal expansion and the increased runoff from glaciers and minor ice sheets. None of this sounds particularly catastrophic just yet, but then it turns out that these predictions are not based on anything particularly relevant: the British Antarctic Survey, in 2008, made it clear that the IPCC had not included the source of nearly 100% of the world’s potential ice melt – the major ice caps of Antarctica and Greenland – simply because they had little idea of how the ice caps would behave in a heating world:
Thus, the most peer-reviewed piece of climate science ever written turns out to be completely inadequate when it comes to estimating the level of disruption associated with a very important aspect of climate change: the rising seas. If Antarctica contains 90% of the world’s land ice (sea ice, like that in the Arctic, does not directly cause the oceans to rise when it melts) and Greenland contains most of the rest, then what’s going to happen when they start to melt with a vengeance, and when are they going to start melting? Official science is mute on the subject.