Recent research works say that climate change may not be as catastrophic as some predictions claim, reports Geoffrey lean
All right, I accept that this Arctic April may seem an incongruous time to address global warming. But there are important, and possibly hopeful, developments in the complex, contentious world of climate science that might finally give us all a sense of spring. For recent research works say that climate change might not be as catastrophic as the gloomiest predictions suggest.
The research, moreover, comes at a time when many experts are beginning to despair that warming can be prevented from running out of control. Six weeks ago, for example, Prof Sir Robert Watson — the deeply respected former chairman of the Intergovernmental Panel on Climate Change (IPCC) — said he believed the world had now missed its chance to keep the average rise in global temperature to less than 2C — the level at which dangerous effects are thought inevitable. But if the new research is right, it might be held below this ominous threshold after all, if determined worldwide action is taken.
Prediction, as they say, is tough, especially when it’s about the future — and that’s especially true when it comes to the climate, whose complexity we only partially understand. It is, as we all know, naturally immensely variable. And the effect of human intervention is subject to long timelags: It will be decades, even centuries, before the full consequences of today’s emissions of carbon dioxide become clear.
As a result, scientists and policymakers draw on the past to predict the future. Until now, they have therefore placed much weight on the rapid temperature increases in the Eighties and Nineties. But for at least a decade, these have dramatically slowed, even as carbon dioxide emissions have continued to increase.
None of this justifies the frequent claim by climate sceptics that global warming has stopped, and may now reverse. long lulls have occurred before, only for temperatures to resume their relentless rise. And eight of the nine hottest years on record have still all occurred since 2000. But it does suggest that the rapid recent warming may have been as anomalous as the present pause.
It also raises the possibility that carbon dioxide may be less potent than has been thought in heating the planet. Again, this is not to say, as some sceptics attest, that it is innocent — the science showing that it is a greenhouse gas has been established for more than 150 years and accords with the very laws of physics. But it may be less guilty than once supposed. And this is reinforced by recent findings that emissions of soot or black carbon are causing twice as much warming as previously estimated, meaning that the contribution of CO2 must be correspondingly less.
The new research focuses on the arcane but crucial issue of “climate sensitivity”. This is normally expressed as the amount of warming that would eventually result from doubling the amount of carbon dioxide in the atmosphere from its level before the Industrial Revolution — something which, on present trends, we will achieve in the next few decades.
The resulting increase has long been put at between 1.5C and 4.5C (the threefold range itself gives some idea of how little is known): The best guess has been 3C, which would be likely to have devastating effects on the climate. But the latest findings — which stretch over several papers from different, well-established scientists — suggest that the rise may be towards the lower end of that big range, possibly less than the 2C danger level.
The researchers themselves are quick to emphasise that their results should not diminish attempts to combat climate change. Their research could be wrong; after all, other equally distinguished scientists have concluded that climate sensitivity is much greater. Even if it is right, their new estimates for temperature rise still range widely, and the upper end still exceeds the danger mark.
Furthermore, the actual effects of temperature rises in the real world can blow away such calculations. Sea ice in the Arctic, for example, has already shrunk to levels not expected to occur for decades — and has done so during the current slowdown in overall global temperature rises.
Besides, a broader problem remains: On present policies, atmospheric CO2 levels will not stop rising when they reach the doubling point, but go on soaring past it — meaning that the world will still reach the danger point, even if more slowly.
So while governments must urgently adopt measures to cut emissions of black carbon — mainly from diesel engines and inefficient Third World cooking stoves — they will also have to do much more to control carbon dioxide.
The new research might just give the world a much-needed breathing space. But it would be foolhardy to breathe out for long.
The Daily Telegraph