Publisher : Macmillan Publishers Limited.
Place of publication :
Publication year : 2009
Thematic : Climate Change and Biodiversity
Language : English
Note
Thinking about worstcase scenarios is nothing new — climate scientists have been doing it for more than 20 years. In 1988, after intense heat waves baked the eastern and central United States, Robert Watson, later to chair the Intergovernmental Panel on Climate Change (IPCC), and I briefed Bill Bradley, the Democrat senator for New Jersey, on the risks of disproportionate surprises from rapid, major climate change. The nature of those surprises was then, as it is now, unclear in details, although we had our hunches. What is new is the assertion that we know the level of warming required to pass tipping points for potentially irreversible outcomes — for example, the risk of unstoppable ice sheet melt in Greenland1. In truth, we don’t know the precise values for tipping points, but we can reasonably estimate with medium confidence by looking at palaeoclimates and recent ice sheet behaviour2. For Greenland, I estimate, after listening to expert judgements, a few per cent chance that meltwater transporting heat downward has already begun to obliterate ice cover irrevocably. At 1 °C more, I’d up my odds to maybe 25% and at 2 °C to 60%. At 3 °C, because the system is highly non-linear, to 90%. Deficiencies in current knowledge allow us to make only subjective probabilistic estimates that must be revised with new knowledge. But what if the worst-case scenario came to pass? An atmosphere in 2100 with 1,000 parts per million of carbon-dioxide equivalent would be catastrophic. To understand the effect of this, we need to peer into what Harvard University economist Marty Weitzman calls the ‘fat tail’3 of the probability distribution for climate damage. Although the likelihood is uncertain — and probably low — we should give these events more attention because not doing so could be potentially disastrous.
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Keywords : Multiple stressors
Encoded by : Mae Belen Llanza
