Grim surprises on the climate front
Two new things on the climate front this week, both bad news. Hurricanes used to be like drive-by shootings: one pass, one hit and then gone. Now they’re starting to come back for a second hit.
And until now scientists only worried about the West Antarctic ice-shelf sliding into the sea (which would add three or four metres to sea-level). But they have just discovered that the main ice-sheet that covers Eastern Antarctica, 10 times bigger, is also in motion (potentially 52 metres of sea-level rise).
Why do we keep being ambushed by bad news like this?
“Thirty years of climate science has given us so much understanding, and what I now see very clearly as a red thread during that entire journey is that the more we learn about the Earth system, the more reason for concern we have,” Johan Rockström, director of the Potsdam Institute for Climate Impact Research, told me three years ago.
“People think we raise the alarm because human pressures are increasing, but that’s not the case at all. It’s just that we are learning how the planet works, and the more we learn the more vulnerable she is.”
“When humans started this massive global experiment of putting pressure on the planet, with greenhouse gases and cutting down forests and loading nutrients into the oceans, what did the Earth system do?
“It responded by buffering and buffering and buffering, and dampening the impacts, just shoving our planetary debt under the carpet, because we were so far away from the tipping point that the systems had huge redundant capacity — what we call resilience.”
That was largely still true three years ago, but cracks are now appearing in that wall of resilience. Events that were not expected to happen so early in the warming process, or ever happen at all, like tropical storms that hang around for weeks, are happening right now.
Hurricane Freddy started in the usual place in early February, off northwestern Australia. It followed the usual path 8,000 kilometres west across the Indian Ocean to the coast of East Africa. It was the biggest cyclone ever to hit Madagascar and the Mozambique coast, but that’s not the big deal.
Hurricanes usually lose power soon after they go over land. The big deal is that Freddy went back out to sea, gathered more energy from the warm surface water and came back for a second bite this week. Hundreds more dead in Mozambique and even in Malawi, far from the sea.
If this can happen with cyclones in the Indian Ocean, sooner or later it will also happen in the Pacific with typhoons smashing into countries from Japan to the Philippines and with hurricanes hitting the Caribbean and North America. We have crossed some sort of invisible threshold.
The other bad news is the discovery that East Antarctica, which contains 90 per cent of the world’s ice, is not the stable, deep-frozen place the scientists hoped and believed it was. Australian scientists now think that in at least two places, Denman and Totten glaciers, megatonnes of ice are sliding into the sea each year.
There may be more glaciers like that, and an urgent search is now underway to determine how imminent the threat of accelerated sea level rise is. Even a couple of extra metres in this century would cause further huge disruption and make the other changes we must make even harder to achieve. But we should have expected this sort of surprises.
Most big changes in natural systems are “non-linear”: abrupt and often irreversible lurches, not smooth transitions. Human beings think about climate in terms of gradual change, mainly because the alternative is even more frightening, so we will continue to be surprised.