From Spencer Weart, Hastings-on-Hudson, New York, US
Graham Lawton does well to point out that a civilisation-destroying climate catastrophe with warming of 4°C to 5°C, also known as the “business as usual” scenario, is no longer the most likely outcome, if indeed it ever was(14 January, p 28).
However, as he acknowledges, there is much uncertainty in our understanding of the climate system. Assessments say that, under current global policies, the most likely rise by 2100 will be about 2.7°C. But that is only the midpoint of a range, with a roughly 5 per cent risk that the rise will go somewhere above 3.5°C.
If we get that much heating, it would still be hard to sustain an even partially prosperous and liberal civilisation. Faced with this all-too-plausible risk, the world needs to accelerate its efforts. As a noted climatologist once said: “Nobody would board an aircraft with a 5 per cent risk of crashing.”
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