The world is likely to overshoot 1.5°C of warming within the next few years, a report by the UN Environment Programme (UNEP) acknowledges. However, it says it is still possible to cool the planet back down to this level by the end of the century. It isn’t impossible, but it certainly isn’t the most likely outcome.
The goal of limiting the increase in the average global surface temperature to 1.5°C above pre-industrial levels looked implausible even back in 2015, when it was adopted as part of the Paris Agreement. The UNEP report can be seen as an “official” acknowledgment of what many have been saying for years: that it is now certain that we are going to blast right past this limit. The secret weapon that could finally force climate action But some aren’t giving up on the target.
There are no good outcomes if we remain above 1.5°C, says Inger Andersen at UNEP. But now we need to approach it differently, from above.” Much of the report looks at the consequences of overshooting 1.5°C and the need for adaptation to cope with the severe impacts this will bring. The report focuses on a scenario in which rapid emissions cuts and massive-scale removal of carbon dioxide from the atmosphere result in a return to 1.5°C of warming by the end of the century.
But achieving this would require limiting temperature rises to no more than 1.8°C, says Roberts. Beyond this, there will be cascading effects from all the irreversible changes that make it much harder. However, restricting warming to this level requires a halving of global emissions by 2035, says report author Joeri Rogelj at Imperial College London.
That seems highly unlikely given that emissions are still rising worldwide. In addition to emissions cuts, the scenario envisaged in the report also requires carbon removal on a truly gigantic scale – enough not just to balance out hard-to-tackle emission sources, such as farming, and achieve net zero, but to go well beyond that to remove around 10 gigatonnes of CO2 each year. That compares with current emissions of around 40 gigatonnes.
The ‘doomsday’ glacier’s giant ice shelf is about to break away This means scaling up carbon removal by a factor of around 100,000, says Reto Knutti at ETH Zurich in Switzerland, who wasn’t involved in the report. Cheap forms of carbon removal, such as planting forests, can’t be scaled up this much because there isn’t enough land. Direct air capture could be scaled up, but it is really expensive, he says.
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