A false sense of security

One way to do that is to average out temperature or precipitation data during the previous 30 years; there must be clear evidence of change over time, and not just a flash-in-the-pan aberration caused by natural variability.

Clearly, it is no good taking one warm year in isolation as evidence of global warming. But, while statistically correct, using a 30-year average to track trends may lead us into missing a sudden transition when some threshold, unbeknown to us, has been crossed. We could then find ourselves irrevocably committed to a new climate regime.

We are all aware that the weather is never quite the same from one year to the next. That is all part of the natural variability of climate. It is the task of climatologists to tease out any change to climate, such as global warming, from all that variability.

In 1990 the Intergovernmental Panel on Climate Change estimated that global emissions must immediately be reduced by over 60 per cent in order to stabilise carbon dioxide in the atmosphere at a reasonably ‘safe’ level. Since 1990, however, global emissions have risen by 10 per cent. Unless immediate and dramatic action is taken to massively reduce our greenhouse gas emissions,...

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