Despite decades of warning, global emissions still aren’t falling

ABCDstock/Shutterstock

It is now impossible for the world to limit global warming to 1.5°C above pre-industrial levels, with emissions on track to cause 2.8°C of warming by the end of the century, the UN says.

Despite increasingly urgent warnings from scientists outlining the dangers of warming above 1.5°C, global emissions aren’t yet falling and governments around the world aren’t doing anywhere near enough to decarbonise their economies.

The only way to meet the 1.5°C target now is by “overshooting” that goal in the short term, the UN said in its latest Emissions Gap report, before relying on vast amounts of global cooling, delivered via technologies such as direct air capture, in the latter half of the century.

This “lowest possible” overshoot scenario would see the global temperature rise peak at 1.7°C to 1.8°C, with a 50 per cent chance of temperatures falling back to 1.5°C by 2100. To deliver this, the world would need to cut emissions by 18 per cent by 2030, 45 per cent by 2035 and 69 per cent by 2040, relative to 2025 levels. Under current climate pledges, emissions will only fall by 5 to 8 per cent by 2030, and 11 to 15 per cent by 2035.

Many scientists are hugely sceptical that the lowest possible overshoot scenario is politically and technologically feasible, given the rapid pace of emissions cuts required and the huge volume of mechanical and natural cooling that would be needed to reduce global temperatures after 2050 to achieve it.

“We don’t know whether we can overshoot,” says Bob Watson, emeritus professor at the University of East Anglia in the UK and former chair of the Intergovernmental Panel on Climate Change. “We don’t know if any of those technologies are real, and so when people assume that we can meet 1.5°C or 2°C, and the assumption is based on overshooting and coming back, I think they’re in cuckoo land.”

Last year’s Emissions Gap report saw the UN warn that overshooting 1.5°C was now inevitable. This year’s analysis sets out new “overshoot pathways” designed to keep the 1.5°C goal – a political totem for many countries – on life support. It calls on nations to focus on delivering the “lowest possible” 1.5°C pathway.

“Overshoot is not surrender. We can still keep it as small and as short as possible – and bring temperatures back below 1.5 degrees by the end of the century,” UN Secretary-General António Guterres said in a statement.

But the UN’s new report makes it clear how far off track the world still is to deliver even this “limited overshoot” pathway. Current national policies put the world on track for 2.8°C of warming by the end of the century. If nations meet all their climate promises, that is lowered to 2.1°C. This is worse than last year’s projection of 1.9°C of warming, driven mainly by the US’s exit from the UN climate process.

Joeri Rogelj at Imperial College London says overshoot should be seen “as a failure that we try to rectify”. But he says there is still value in using the 1.5°C goal, rather than adopting a higher temperature goal that could be achieved without overshoot. “The target is still to limit harm to vulnerable and poor populations, and that we don’t do by resetting the target to an inadequate limit of 2°C, or 2.5°C,” he says. “In the public debate, this failure to stay within this most ambitious limit should re-emphasise the need to stay as close to it as possible.”