World must cut emissions by 18% in four years ‘to find our way back’, UN says

UN warns of disastrous climate overshoot if emissions not cut by 18% in four years

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The world needs to cut carbon emissions by nearly a fifth in the next four years, and by close to half within a decade, to avoid overshooting climate targets by a disastrous margin, according to the UN Environment Programme (Unep).

Global carbon output appears to have stalled, with emission levels in 2025 being broadly similar to those of the previous year. However, Unep analysts were wary of calling it a peak or plateau, given the vast uncertainties of geopolitics and an increased reliance on fossil fuels, despite strong growth in renewable energy.

Cutting greenhouse gases by 18% by 2030, and by 45% by 2045, would yield a good chance of limiting temperature rises to 1.7C above preindustrial levels. This would still allow events such as the record heatwaves of the last few months to become frequent and common, but could help prevent them from getting drastically worse.

Governments were warned for years that time was running out, said Inger Andersen, the executive director of Unep. She urged countries to keep the 1.5C goal – the centrepiece of the Paris climate agreement – and to make the overshoot as brief and as short as possible.

The US, the world’s second biggest emitter, after China, has withdrawn from the Paris climate agreement and is threatening to reverse its longstanding trend of falling greenhouse gas emissions. Other countries appear to have been affected by US intransigence – pledges made last year on greenhouse gases were noticeably weak, according to UNEP analysis.

Policy has also not kept up with pledges: on current policies around the world, temperatures would rise to 2.8C. Every five years of greenhouse gas emissions at current levels pushes up forecasts of global heating by 0.1C. Scientists also fear that the greater the margin by which we exceed 1.5C, the greater the likelihood of triggering tipping points in the climate system.