In the mid-1970s it was briefly fashionable for journalists to write scare stories about the recent cooling of the globe, which was presented as undiluted bad news. Now it is fashionable for them to write scare stories about the recent warming of the globe, which is presented as undiluted bad news. Here are two quotes from the same magazine three decades apart. Can you tell which is about cooling and which about warming?
The weather is always capricious, but last year gave new meaning to the term. Floods, hurricanes, droughts – the only plague missing was frogs. The pattern of extremes fit scientists’ forecasts of what a —-world would be like. Meteorologists disagree about the cause and extent of the trend, as well as over its specific impact on local weather conditions. But they are almost unanimous in the view that the trend will reduce agricultural productivity for the rest of the century…
The longer the planners delay, the more difficult will they find it to cope with climatic change once the results become grim reality. The point I am making is not that one prediction proved wrong, but that the glass was half empty in both cases. Cooling and warming were both predicted to be disastrous, which implies that only the existing temperature is perfect. Yet climate has always varied; it is a special sort of narcissism to believe that only the recent climate is perfect. (The answer by the way is that the first one was a recent warning about warming; the second an old warning about cooling – both are from Newsweek.)
So much for the outlying risks. Now consider the IPCC’s much more probable central case: a 3°C rise by 2100. (I say more probable, but note that the rate o f increase of temperature will have to be double that experienced in the 1980s and 1990s to hit this level – and the rate has been decelerating, not accelerating.) Count the cost – and benefit – of the extra warmth in terms of sea level, water, storms, health, food, species and ecosystems. Sea level is by far the most worrisome issue, because thecurrent sea level is indeed the best of all possible sea levels: any change – up or down – will leave ports unusable. The IPCC forecasts that average sea level will rise by about 2-6 millimetres a year, compared with a recent rate of about 3.2 millimetres a year (or about a foot per century). At such rates, although coastal flooding will increase slightly in some places (local rising of the land causes sea level to fall in many areas), some countries will continue to gain more land from siltation than they lose to erosion.
The Greenland land-based ice cap will melt a bit around the edge – many Greenland glaciers retreated in the last few decades of the twentieth century – but even the highest estimates of Greenland’s melting are that it is currently losing mass at the rate of less than 1 per cent per century. It will be gone by a d 12,000. O f course, there is a temperature at which the Greenland and west Antarctic ice caps would disintegrate, but according to the IPCC scenarios if it is reached at all it is certainly not going to be reached in the twenty-first century. As for fresh water, the evidence suggests, remarkably, that, other things being equal, warming will itself reduce the total population at risk from water shortage. Say again? Yes, reduce. On average rainfall will increase in a warmer world because of greater evaporation from the oceans, as it did in previous warm episodes such as the Holocene (when the Arctic ocean may have been almost ice-free in summer), the Egyptian, Roman and medieval warm periods.
The great droughts that changed history in western Asia happened, as theory predicts, in times of cooling: 8,200 years ago and 4,200 years ago especially. If you take the IPCC’s assumptions and count the people living in zones that will have more water versus zones that will have less water, it is clear that the net population at risk of water shortage by 2100 falls under all their scenarios. Although water will continue to be fought over, polluted and exhausted, while rivers and boreholes may dry up because of over-use, that will happen in a cool world too. As climate zones shift, southern Australia and northern Spain may get drier, but the Sahel and northern Australia will probably continue their recent wetter trend. Nor is there any evidence for the oft-repeated assertion that climate will be more volatile when wetter. Ice cores confirm that volatility of climate from year to year decreases markedly when the earth warms from an ice age. There will probably be some increase in the amount o f rain that falls in the most extreme downpours, and perhaps more flooding as a result, but it is a sad truth that the richer people are, the less likely they are to drown, so the warmer and richer the world, the better the outcome