Covid-19 lessons can help in climate battle

Human beings respond well to a crisis that is familiar, especially if it is also imminent. They don’t do nearly as well when the threat is unfamiliar and still apparently quite distant. Consider our response to the current coronavirus threat.

Countries in East Asia with recent experience of similar viruses (SARS, etc.) immediately responded with ‘‘test, track and isolate’’ drills, plus instant lockdowns if the virus had already gained a foothold in the population.

Other countries, just as rich and welleducated, had the same information, but they still waited several months before taking emergency measures that upset the comfortable routine of their lives.

So the United States, Britain and France all ended up with death rates per millionmore than 50 times higher than China, Korea and Japan.

The same applies to global heating, except that in this case we are all Americans. None of us has prior experience of a genuine climate crisis, and although we have known enough about what’s going to happen to justify urgent action for 30 years now, we have done nothing decisive about it.

We have lots of ‘‘clean’’ technology, but total demand for energy has grown so fast that we are still getting 80 per cent of our energy from fossil fuels. Realistically, this is not going to changemuch.

A truly serious response to the climate threat will therefore come only when it is actually starting to hurt. Unfortunately, by then it will probably be too late.

The Earth system plays by its own rules. It will absorb new inputs like warming for a long time while changing as little as possible: it’s a ‘‘homeostatic’’ system.

We are still benefiting from this feature now: a full degree Celsius of warming already, and not much to show for it except hotter summers, shorter winters and bigger storms. But when the pressure on the climate system gets too great it is liable to charge off in unpredictable directions at high speed.

‘‘Non-linear change’’, they call it, and we won’t like it a bit. Hundreds of millions, maybe billions, will start to die.

Then we’ll be ready to make great changes to save ourselves, but it will be too late. Human systems will be collapsing under the impact of famines, wars and endless waves of refugees, and besides once the climate hits non-linear change it’s almost impossible to bring it back. We’re stuckwith wherever it ends up, whether that new state will support a large human civilisation or not.

How far ahead is this calamity? We probably have at least a decade or two. Will we end all our greenhouse gas emissions in that time? Probably not.

So the crisis almost certainly will arrive, and then we will finally be willing to make radical changes. What we will need at that point ismore time. That’s whywe will need geoengineering.

Geoengineering is not a cure; it is a way of temporarily counteracting the warming caused by our emissions, by reflecting a small part of the incoming sunlight in one way or another.

In fact, you could say that it is ‘‘positive’’ geoengineering, as opposed to the large-scale ‘‘negative’’ geoengineering we have been doing for the past two centuries by dumping huge amounts of warming gases into the atmosphere.

When we are finally ready to act on global warming, we will need time to make the changes that are required to preserve this global civilisation and the biosphere it now dominates. Only geoengineering can create that window.

We don’t need to start geoengineering now. It would be wonderful if we never have to do it, but that would take a miracle.

We cannot know how long we would have to go on doing it, either: long enough to get the carbon dioxide in the atmosphere back down to a safe level, certainly, which would be at least a matter of decades.

But even without knowing the answers to these questions, we clearly need to speed up research and testing of the various potential techniques for geoengineering now.