Why did 1.5°C fail and setting a new limit would make things worse

More than a decade since the 2015 Paris climate conference, it’s hard not to feel that we’ve been treading water on climate action at best. Sure, there are far more electric vehicles on the road, and renewables now produce more electricity globally than coal. But we continue to pump out more than 41 gigatonnes of carbon dioxide each year, while fossil fuel companies plan to expand and governments fight back with environmental measures.

There was real optimism in Paris as countries committed to efforts to limit the global average temperature increase to 1.5°C above pre-industrial levels. Ten years on, that ambition is dead in the water in every way. That’s the mechanism used to define when our world will exceed 1.5°C, however the year this will happen won’t likely be officially confirmed until 2040 or so – ten years after it actually happens.

The 1.5°C mark has been linked to the threshold of dangerous climate change and as such has been at the heart of all aspects of climate policy. We have been warned that exceeding the 1.5°C threshold greatly increases the risk of overturning critical elements of the climate system, leading to further warming and catastrophic impacts, but even this has not led to the emissions action the science calls for.

So what happened? Why did we fail? At the heart of the problem is the fact that 1.5°C has been seen by many not as a limit but as a target, and while the limit is something we try to keep below, the target is something we aim for.

The world had warmed by not much more than 1°C by the time of the Paris conference, and the prevailing rate of warming was measured at about 0.18°C per decade. This gave the impression that we had plenty of time to act, and the usual suspects took advantage. Governments and fossil fuel corporations that want to continue to jump-start climate action have argued that business as usual can continue for now and that the time for serious action is not yet ripe. As a result, burning fossil fuels continues to add 37 gigatons of carbon dioxide to the atmosphere each year.

As we move above 1.5°C, there is heated debate about a new planetary star to replace it. Some have suggested using an entirely different measure of our progress—or lack thereof— such as the rate of use of renewable energy. But the key metric really has to be global temperature rise. This is it and a benchmark against which the response of the climate system is measured, and can provide a comparison to ancient episodes of rapid warming that swept our world. It is also a thing that everyone understands, although many still do not understand its meaning.

In this respect, with every fraction of a degree now critical, some have suggested looking at 1.6°C as the new limit, or perhaps 1.7°C. But neither will cut it, firstly because they will once again be seen as targets for those who game the system, and secondly because at the current rate of warming – 0.27°C per decade – both will be exceeded as early as the mid-2030s. The reality is that there is no snowball in hell that we will act on emissions fast enough to stay this side of one of these brands.

The truth is that adopting a new limit that quickly becomes a target would actually make things worse, while tying politics to it would set us up for failure again. So maybe we should forget about limits altogether and instead focus on some effective means of marking the annual average global temperature increase for all to see. This would first require a methodology that allows this number to be determined immediately, rather than waiting 10 years. However, there is already a way to do it developed by Richard Betts of the UK Met Office, the country’s national meteorological service, and his colleagues.

Then we need some visual means to show this in a way that everyone can understand – like an Earth thermometer that updates at 12-month intervals. Following the example of the Bulletin of Atomic Scientists, which each January announces the time on the Doomsday Clock of existential threats to civilization, perhaps a similar annual jamboree could call attention to the sharp increase in global temperature on the same day each year, next to those tipping points we are on the verge of crossing, or have already crossed. This would provide an unequivocal measure of the shocking impact our activities are having on the planet’s temperature, signaling the closure of an increasingly dangerous future without urgent action.

Bill McGuire is Emeritus Professor of Geophysics and Climate Risk at University College London. His next book: The Fate of the World: The History and Future of the Climate Crisispublished by HarperNorth in May.

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