The Rational Optimist (38 page)

If, that is, the climate does not lurch into chaos.

Climate

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 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
.)

I could plunge into the scientific debate and try to persuade you and myself that the competitive clamour of alarm is as exaggerated as it proved to be on eugenics, acid rain, sperm counts and cancer – that the warming the globe faces in the next century is more likely to be mild than catastrophic; that the last three decades of relatively slow average temperature changes are more compatible with a low-sensitivity than a high-sensitivity model of greenhouse warming; that clouds may slow the warming as much as water vapour may amplify it; that the increase in methane has been (erratically) decelerating for twenty years; that there were warmer periods in earth’s history in medieval times and about 6,000 years ago yet no accelerations or ‘tipping points’ were reached; and that humanity and nature survived much faster warming lurches in climate during the ice ages than anything predicted for this century. There are respectable scientific arguments to support all these arguments – and in some cases respectable scientific ripostes to them, too. But this is not a book about the climate; it is about the human race and its capacity for change. Besides, even if the current alarm does prove exaggerated, there is now no doubt that the climate of this planet has been subject to natural lurches in the past, and that though luckily there has been no huge lurch for 8,200 years, there have been some civilisation-killing perturbations – as the ruins at both Angkor Wat and Chichen Itza probably testify. So if only hypothetically, it is worth asking whether civilisation could survive climate change at the rate assumed by the consensus of scientists who comprise the Intergovernmental Panel on Climate Change (IPCC) – that is, that the earth will warm during this century by around 3°C.

However, that is just a mid-range figure. In 2007 the IPCC used six ‘emissions scenarios’, ranging from a fossil-fuel-intensive, centennial global boom to something that sounds more like a sustainable, groovy fireside sing-along, to calculate how much temperature will increase during the century. The average temperature increases predicted for the end of this century ranged from 1.8°C to 4°C above 1990 levels. Include the 95 per cent confidence intervals and the range is 1–6°C. In some cities the warming will be – has already been – even more, thanks to the ‘urban heat island’ effect. On the other hand, all experts agree that the warming will happen disproportionately at night, in winter and in cold regions, so cold times and places will get less cold more than hot ones will get hotter.

As for what might happen after 2100, in 2006 the British government appointed a civil servant, Nicholas Stern, to count the potential cost of extreme climate change far into the future. He came up with the answer that the cost was so high that almost any price to mitigate it now would be worth paying. But he only managed this by first cherry-picking high estimates of harm; and second using an unusually low discount rate to measure the present value of future loss. Where the Dutch economist Richard Tol had estimated costs as ‘likely to be substantially smaller’ than $14 per tonne of carbon dioxide, Stern simply doubled the figure to $29 per tonne. Tol – no sceptic – called the Stern report alarmist, incompetent and preposterous. As for discount rates, Stern used 2.1 per cent for the twenty-first century, 1.9 per cent for the twenty-second, and 1.4 per cent for subsequent centuries. Compared with a typical discount rate of about 6 per cent, this multiplies the apparent cost of harm in the twenty-second century one hundredfold. In other words, he said that a life saved from coastal flooding in 2200 should have almost the same spending priority
now
as a life saved from AIDS or malaria today. Hordes of economists, including notable names like William Nordhaus, quickly pointed out how this made no sense. It implies that your impoverished great great great grandfather, whose standard of living was roughly that of a modern Zambian, should have put aside most of his income to pay your bills today. With a higher discount rate, Stern’s argument collapses because, even in the worst case, harm done by climate change in the twenty-second century is far less costly than harm done by climate-mitigation measures today. Nigel Lawson asks, reasonably enough: ‘How great a sacrifice is it either reasonable or realistic to ask the present generation, particularly the present generation in the developing world, to make, in the hope of avoiding the prospect that the people of the developing world in a hundred years time may not be 9.5 times as well off as they are today, but only 8.5 times?’

Your grandchildren will be that rich. Do not take my word for it: all six of the IPCC’s scenarios assume that the world will experience so much economic growth that the people alive in 2100 will be on average four to eighteen times as wealthy as we are today. The scenarios assume that the entire world will have a mean standard of living somewhere between today’s Portugal and Luxembourg, and even the citizens of developing countries will have incomes between those of today’s Malaysians and Norwegians. In the hottest scenario, income rises from $1,000 per head in poor countries today to more than $66,000 in 2100 (adjusted for inflation). Posterity in these futures is staggeringly wealthier than today, even in Africa – an interesting starting assumption for an attempt to warn us of a terrible future. Note that this is true even if climate change itself cuts wealth by Stern’s 20 per cent by 2100: that would mean the world becoming ‘only’ two to ten times as rich. The paradox was stark when the Prince of Wales said in 2009 that humanity had ‘100 months left to take the necessary steps to avert irretrievable climate and ecosystem collapse’, then went on in the same speech to say that, by 2050, there will be nine billion people on the planet, mostly consuming at Western levels.

The reason for these rosy assumptions about wealth is that the only way the world can get that hot is by getting very rich through emitting lots of carbon dioxide. Many economists think these futures, wonderful as they sound, are unrealistic. In one IPCC future, world population reaches fifteen billion by 2100, nearly double what demographers expect. In another, the poorest countries grow their per capita income four times as fast as Japan grew in the twentieth century. All the futures use market exchange rates instead of purchasing power parities for GDP, further exaggerating warming. In other words, the highend projections have pretty wild assumptions, so the 4°C warming, let alone the unlikely 6°C, will only happen if it is also accompanied by truly astonishing increases in human prosperity. And if it is possible to get so prosperous, then the warming cannot have been doing much economic harm along the way.

To this some economists such as Martin Weitzman reply that even if the risk of catastrophe is vanishingly small, the cost would be so great that the normal rules of economics do not apply: so long as there is some possibility of a huge disaster, the world should take all steps to avoid it. The trouble with this reasoning is that it applies to all risks, not just climate change. The annual risk of collision with a very large asteroid, such as wiped out the dinosaurs, is put at about one in 100 billion. Given that such an event would greatly reduce human prosperity, it seems to be rather cheap of humankind to be spending as little as $4m a year to track such asteroids. Why are we not spending large sums stockpiling food caches in cities so that people can survive the risks from North Korean missiles, rogue robots, alien invaders, nuclear war, pandemics, super-volcanoes? Each risk may be very unlikely, but with the potential harm so very great, almost infinite resources deserve to be spent on them, and almost nothing on present causes of distress, under Weitzman’s argument.

In short, the extreme climate outcomes are so unlikely, and depend on such wild assumptions, that they do not dent my optimism one jot. If there is a 99 per cent chance that the world’s poor can grow much richer for a century while still emitting carbon dioxide, then who am I to deny them that chance? After all, the richer they get the less weather dependent their economies will be and the more affordable they will find adaptation to climate change.

Warmer and richer or cooler and poorer?

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 of 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 the current 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
AD
12,000. Of 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 of 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 out come.

The same is true for storms. During the warming of the twentieth century there was no increase in either the number or the maximum wind speed of Atlantic hurricanes making landfall. Globally, tropical cyclone intensity hit a thirty-year low in 2008. The cost of the damage done by hurricanes has increased greatly, but that is because of the building and insuring of expensive coastal properties, not because of storm intensity or frequency. The global annual death rate from weather-related natural disasters has declined by a remarkable 99 per cent since the 1920s – from 242 per million in the 1920s to three per million in the 2000s. The killing power of hurricanes depends far more on wealth and weather forecasts than on wind speed. Category 5 Hurricane Dean struck the well-prepared Yucatan in 2007 and killed nobody. A similar storm struck impoverished and ill-prepared Burma the next year and killed 200,000. If they are freed to prosper, the future citizens of Burma will be able to afford protection, rescue and insurance by 2100.

In measuring health, note that globally the number of excess deaths during cold weather continues to exceed the number of excess deaths during heat waves by a large margin – by about five to one in most of Europe. Even the notorious one-off death rate in the European summer heat wave of 2003 failed to match the number of excess cold deaths recorded in Europe during most winters. Besides, once again, people will adapt, as they do today. People move happily from London to Hong Kong or Boston to Miami and do not die from heat, so why should they die if their home city gradually warms by a few degrees? (It already has, because of the urban heat island effect.)