On 28 October 2025, United Nations secretary-general António Guterres acknowledged that the totemic goal of the Paris climate agreement is going to be missed: “The truth is that we have failed to avoid an overshooting above 1.5 °C in the next few years”1.
Approaching 1.5 °C: how will we know we’ve reached this crucial warming mark?
Guterres was merely stating the obvious. In 2024, Earth’s global mean surface temperature averaged 1.55 °C above pre-industrial levels2, and the average for 2023–25 is 1.48 °C, perilously close to the limit. Keeping to the Paris target now looks impossible by any realistic measure. Yet this moment should not invite despair. Instead, it demands an urgent reframing of how climate progress is measured and mobilized.
The world today looks very different from that in 2015 when the Paris goal was framed. Although emissions are still rising and global actions on climate change are slow, a lot of progress has been made. Clean energy is expanding rapidly and decarbonization, not fossil fuels, is the new ‘business as usual’. In the first three quarters of 2025, growth in clean electricity generation outpaced that in energy demand for the first time, implying that fossil fuels are being displaced (see go.nature.com/3jvqzcb).
We argue that the main focus of climate action in 2026 and beyond should be on accelerating the clean-energy revolution. And the rate at which clean energy displaces fossil fuels in the global economy should become the key measure of climate progress. Here we describe how such progress can be tracked and incentivized using a metric we call the clean-energy shift. Unlike chasing intangible temperature targets, cleaning up the energy sector is a more-focused battle that the world can win.
Beyond average temperatures
To move forwards, climate scientists and policymakers must first accept that the Paris 1.5 °C target has outlived its usefulness. Although initially valuable as a unifying focus for international efforts to increase mitigation, continuing to emphasize a failed temperature target might produce more harm than good.
One reason is the difficulty of determining when and whether the world has crossed the line. Forecasts suggest that Earth is likely to exceed the 1.5 °C threshold around 2028, for instance (see go.nature.com/4pf95x6). But in the terminology of the Intergovernmental Panel on Climate Change (IPCC), “exceedance” of 1.5 °C refers to the midpoint of a 20-year period at that level3. Confirmation would therefore not come until a decade after the fact.
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Such a target, requiring years of expert interpretation to assess, could never have great salience for decision makers. And it challenges public understanding because, by definition, no person experiences global average temperatures. Moving to a higher number when 1.5 °C is crossed, such as 1.6 °C or 1.7 °C, would only make climate target setting seem arbitrary and unrooted in scientific evidence.
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