WHY ‘ACT NOW’ IS THE RIGHT APPROACH TO GLOBAL WARMING
Repent, for the end of the world is nigh. That is a warning one would expect to come from an evangelical preacher or an environmental doomsayer, not from a sober economist. Yet that is, in essence, what Sir Nicholas Stern, author of the British government’s new report on climate change, is saying.* The tone may be sober, but the conclusion – act now before it is too late – is not.
Hitherto many economists, business-people and politicians, particularly in the US, have argued that, given both the uncertainties and the high costs of taking possibly unnecessary action, the best policy is to wait, see and, if necessary, adapt. The contribution of this report is to reverse that logic. It argues that, given these very same uncertainties and the relatively low costs of acting now, the best policy is action.
How and how convincingly does the review make this case? The answer, I suggest, is: “Sufficiently so.”
The starting point has to be with the consequences of “business as usual”. The underlying scientific argument on this is straightforward. Since the industrial revolution the stock of greenhouse gases in the atmosphere has risen from the equivalent of 280 parts per million (ppm) of carbon dioxide to 430ppm. If current emission trends continue, the stock of greenhouse gases in the atmosphere could more than treble by the end of this century.
Greenhouse gases trap heat, which is why there is abundant life on earth. It is also, argue the scientists, why the earth has warmed by about 0.7°C since 1900. Should current trends continue, temperatures might rise by between 3°C and 10°C by 2100 (see chart). By the middle of this century and, so, within the life-span of many now alive, warming could be between 2°C and 5°C. Since the earth is only 5°C warmer today than during the last ice age, a change of that magnitude would be enormous.
Should the temperature rise by 5°C, there may be adverse effects on crop yields; significant rises in sea levels that threaten developing countries, such as Bangladesh, but also coastal cities, such as London, Shanghai and New York; water shortages affecting more than a billion people; mass extinctions; increasingly intense storms; and, conceivably, huge shifts in the climate system, with local cooling and intense local warming.