Old-fashioned pessimism might actually help us fight climate change

Pessimism is a dirty word in climate policy circles. There are good reasons for this, not least that optimism can spur positive change, while assuming the worst can paralyse us into inaction. But when it comes to climate modelling, some negative thinking could be a good thing.

The Intergovernmental Panel on Climate Change already hedges its bets with a range of models, or pathways, that assess how we might limit warming to 1.5°C, or see carbon emissions continue unabated, or experience many possibilities in between. These pathways are underpinned by thousands of scientific papers, reams of data and the brains of the world’s climate scientists, but, like all models, they are also built on assumptions.

One key assumption in scenarios that keep us below 1.5°C of warming is that, in the near future, we will rapidly perfect technologies that remove carbon dioxide from the atmosphere. This isn’t an unreasonable prediction, given human ingenuity and the strong incentives for doing so. But including carbon capture technologies in these models is a bit like declaring you will balance your household budget with a lottery win — if you can’t cut your outgoings to an affordable level, you had better hope a big prize is on its way.

As two stories in this issue demonstrate, this is a risky approach. A detailed analysis of plans for geological storage of carbon dioxide has found that meeting the levels assumed by many 1.5°C pathways is, if not impossible, then at least highly unlikely (see “Our plans to tackle climate change with carbon storage don’t add up“). The odds of that lottery win aren’t looking so hot. Meanwhile, we have also received an unexpected carbon bill, in the form of melting Arctic permafrost releasing more greenhouse gas than has previously been accounted for (see “Arctic permafrost is now a net source of major greenhouse gases“).

Such revisions in our understanding of climate change are both entirely expected and to be welcomed, but they show that the challenges facing us in the next decade have just got harder. Instead of squeezing climate models until the numbers just about fit the 1.5°C target, perhaps a more pessimistic outlook would better accelerate efforts to limit the damage.