If you realised you had a high temperature, would you throw the thermometer away or call the doctor? The question is rhetorical, because you would certainly call the doctor. When it comes to global warming, however, people hesitate and take refuge in the thought that ‘perhaps the thermometer isn’t working’. But there are claims such as ‘it has been hot in other geological periods too, and even hotter than today’, or ‘the climate has always changed’. These statements are insidious because they are partly true but misleading; in fact: 1. during many hot periods in the distant past, humans would not have been able to survive; 2. the rate of change (warming) has never been as rapid as in the last century; 3. they fail to take into account the complexity of the climate system and the many irreversible changes we risk facing. Among these, the melting of Greenland’s ice sheets will cause a 7-metre rise in sea levels; the thawing of permafrost will release further climate-altering gases into the atmosphere, amplifying the anthropogenic impact; the collapse of the Amazon rainforest will reduce the ability to capture some of the CO₂ emitted; and the disruption of the North Atlantic Ocean circulation will lead to increasingly extreme climates.
Our species has evolved extremely rapidly on a planet where ‘ice’ (the cryosphere) is the primary regulator of the climate, chiefly because it reflects infrared radiation back into space. Implicitly, we now believe we can do without it. In short, too many people are still trying to throw away the thermometer and claim there is nothing to worry about. Amitav Ghosh calls it ‘great blindness’: we fail to see something not because it is insignificant, but because it is enormous. To overcome this impasse, we must understand the difference between ‘geological times’ and ‘historical times’, in which humankind has become the principal ‘geological’ force driving environmental change.
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