Read more: 鈥�Climate change: What we do 鈥� and don鈥檛 鈥� know鈥�
WOULD you jump off a skyscraper? What if someone told you that physicists still don鈥檛 fully understand gravity: would you risk it then?
We still have a lot to learn about gravity, but that doesn鈥檛 make jumping off a skyscraper a good idea. Similarly, we still have a lot to learn about the climate but that doesn鈥檛 make pumping ever more greenhouse gases into the atmosphere a good idea.
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Uncertainty is one of the defining features of science. Absolute proof exists only in mathematics. In the real world, it is impossible to prove that scientific theories are right in every circumstance; we can only prove that they are wrong. This provisionality can cause people to lose faith in the conclusions of science, but it shouldn鈥檛. The recent history of science is not one of well-established theories being proven wrong. Rather, it is of theories being gradually refined. Newton鈥檚 laws of gravity may have been superseded, but they are still accurate enough to be used for many purposes.
In the same way, while there are enormous uncertainties about how the climate will change over the coming decades and centuries, and what the consequences will be, there are also many things that we are now sure of (see 鈥�Climate known: Greenhouse gases are warming the planet鈥�). One of these certainties is that higher levels of atmospheric greenhouse gases have a warming effect. And as ever more evidence comes in about this and other aspects of the climate system, room for hope that we have overstated the problem is diminishing.
In fact, perhaps the biggest source of uncertainty is not to do with the science at all, or the global climate system, but with us.
Will we burn every last drop of fossil fuel? Or will some amazing technological advance make the switch to renewable energy a no-brainer? Will we keep building cities in places vulnerable to sea-level rise, like Shanghai?
鈥淏y the time the need for drastic action becomes blindingly obvious, we will have missed our chance鈥�
No one can answer such questions, but what we can say is that human society is subject to vast inertia. Even if the will to slash emissions were there, it would take decades. Unfortunately the will is not there 鈥� many influential people still deny there is even a problem.
What鈥檚 just as concerning is that so many pay only lip service to the idea. Even politicians who back action to curb global warming are not delivering on their promises. Many of the countries that signed up to the have failed to achieve their very modest targets. Meanwhile, some countries in Europe are signing up to more ambitious goals for reducing emissions by 2030, while still commissioning coal-fired power stations.
By the time the need for drastic action becomes blindingly obvious, the best opportunity to curb harmful change will have been squandered. Yet if draconian action is taken today, any success in limiting warming will be greeted with scepticism that drastic measures were ever worthwhile or even necessary. Perhaps the greatest unknown, then, is how to persuade people to act today to help protect their long-term future, not to mention future generations.
One more thing is certain: only science can reveal how our planet can provide a decent home for billions of people without toppling over the precipice.
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