The 1.5°C target is dead, but climate action needn’t be

As the COP₂₆ climate negotiations were taking place in Glasgow, UK, in November 2021, a new slogan entered the lexicon: “keep 1.5°C alive”. The phrase, on the lips of everyone from politicians to climate scientists, aimed to preserve the goal set six years earlier as part of the Paris Agreement at COP₂₁. In hindsight, this ambition was probably already dead, destined to be deployed only as an empty slogan.

New Scientist began making this argument in 2022, when the public sentiments of experts didn’t reflect their private views or the data we were seeing. Scientists felt trapped, unable to speak out because limiting warming to 1.5°C above pre-industrial levels still remained possible according to the laws of physics, while being impossible with any realistic acknowledgment of the political, social and economic upheaval required.

In the intervening years, there has been a growing realisation that 1.5°C is out of reach, but not a frank conversation about what that means. Now, researchers have for the first time explicitly ruled it out, saying 1.6°C is the best we can hope for, while even higher temperatures are the more likely outcome (see “Best-case scenario for climate change is now 1.6°C of warming”).

Will this finally be enough for policy-makers to sit up and realise that platitudes and slogans aren’t a sufficient form of climate action? Promises to keep any such goal “alive” are pointless without doing the only thing that will prevent temperatures rising: reducing the amount of carbon dioxide and other planet-warming greenhouse gases entering the atmosphere to net zero.

Unfortunately, the phrase “net zero” is losing its true meaning as a description of atmospheric physics, instead being used by many to mean “an environmental policy I don’t like”. This is dangerous, as temperature extremes have us trapped in a vicious cycle of emissions that only a net-zero energy system can break (see “Our efforts to cope with extreme temperatures are making them worse”). If we are to have any hope of limiting warming, we must learn from the mistakes of “keep 1.5°C alive” and not let “net zero” become meaningless.