Over the past few decades, climate scientists have made huge strides in understanding the future climate. But after recent weeks of extreme heat and devastating floods it’s clear that, although climate models have provided good information about overall rising temperatures, they can’t be sure what level of destruction each notch on the thermometer will bring.
Climate modelling is extremely complex, but its fundamentals rely on basic physics – X tonnes of emissions will bring Y increase in temperature, with some error bars. Supercomputers have been able to factor in shifts in land use that will change the reflectivity of the Earth’s surface. Improved temperature records helped verify their findings.
But lately, leading researchers have made a painful confession: even their most sophisticated models can’t yet foresee exactly how Earth systems will respond to those higher temperatures.
The influential Intergovernmental Panel on Climate Change (IPCC) says cranking up global temperature by half a degree will bring much more extreme weather, and it can be more often, more intense, or extended in duration – but exactly how much more, it can’t precisely say.
So, for instance, we’ve already had a global temperature rise of about 1.2C: that’s in line with IPCC projections. Yet the panel couldn’t warn us about the appalling heat dome that’s been searing North America. I can’t find heat domes mentioned in the bible of climate change, the IPCC report. This periodic report inevitably lags behind new science and – under pressure from some governments and industries, as well as a desire not to scaremonger – its pronouncements tend to be conservative.
The models also couldn’t warn us accurately about the emergence of the heat trapped deep in the ocean, which soaks up 90% of the world’s excess warmth. In the 35 years I covered the environment for the BBC, I recall speculation that the warmth could stay deep for decades, perhaps centuries – not that some of it would suddenly burst up to the surface off the coast of northern Britain.
Major uncertainties remain, too, over rainfall. Good information about the future of monsoon rain would be a godsend for farmers who rely upon it – not just in India but in southern China. Unfortunately, good information on precipitation is proving a bit tricky to find.
The macro models also failed to project the effect of current elevated temperatures on ice at both poles. The former IPCC chief, Prof Bob Watson, told me: “I am very concerned. None of the observed changes so far (with a 1.2C temperature rise) are surprising. But they are more severe than we predicted 20 years ago, and more severe than the predictions of five years ago. We probably underestimated the consequences.”
This is a massive admission. He added: “Scientists are only now starting to understand the response of large ice sheets in Greenland and Antarctica – and it is very disturbing.”
Prof Jane Francis, director of the British Antarctic Survey, told me a few months ago the latest science on ice melt was “truly scary”.
Watson said at current rates the world would almost certainly exceed the agreed maximum temperature rise of 1.5-2C. We would be lucky to get away with 2.5C, he said. More likely, we’re heading towards 3C.
That number positively frightens many climate scientists. But, as India starts stockpiling rice with a temperature rise of 1.2C, what useful advice can scientists offer for a 3C world? Just how bad will things be by then?
Should holidaymakers avoid buying homes in Greece? China is vulnerable to extremes – how should its economy adapt? The US has considered itself less vulnerable. But tell that to New Yorkers choking on wildfire smoke, or people in Phoenix trapped under that heat dome.
While immediate harm to people grabs the headlines, what’s even more destructive could be the impact of heat and humidity on food production for an expanding population. A global shift towards a plant-based diet could halve the land and water used for agriculture – and halve the carbon emissions – but politicians fear angering voters by recommending a dietary shift.
Facing all this gloom means we need imagineers as well as climatologists. Watson said civilisation will still exist in the future, but with much worse living conditions. But what sort of a degraded civilisation might that be? By then we may even have triggered some natural tipping points that could result in a massive release of trapped methane in the tundra – let’s hope not.
What we do know is that so far, the effects of heating the climate are sooner and worse than many scientists projected (in public at least). This has policy implications. The world has agreed to cut emissions to net zero by 2050, but the UN secretary general, António Guterres, says rich countries should be aiming to squeeze the timetable to 2040. But what is the use of a net zero policy if it relies in part on planting trees that may shrivel in future drought or crackle in wildfire?
To make matters worse, climate heating is one thing on a list of huge environmental problems – including pollution of the air and water, destruction of wildlife habitats, overfishing, insect population declines, loss of birds, plastic pollution, nitrates, soil loss and more.
Watson says we don’t know how these phenomena will interact with each other, but he urges politicians to err on the side of caution, as the stakes are so very high. Every 0.1C warming matters, scientists say: 1.5C is better than 1.6C. That in turn is less bad than 1.7C.
As the barrage of bad news continues, all we can be certain of is that there are many climate surprises lying ahead of us. Governments, companies and individuals need to urgently squeeze down emissions to insulate ourselves as far as possible from what we may face.
Roger Harrabin is an energy and environment analyst and a former BBC correspondent
