Does it matter? In some corners, discarding the 1.5-degree goal looks like a possibly welcome development, since the target was in many ways flawed to begin with. A global average temperature rise may be a useful shorthand measure of the state of play, but it probably isn’t the best guide to climate disruptions, since temperatures and expected effects vary significantly from place to place. Global average temperature is also not so tightly linked to human activity, since a certain amount of emissions could produce a relatively wide range of warming levels. (That’s why our uncertainty about climate sensitivity is worrying.)
To some, the target was somewhat arbitrary to begin with, reflecting some earlier calculations about climate safety that imply much lower thresholds of concern. The base line historical period was not exactly a climate paradise; it featured many of the modern world’s most devastating disasters and famines — a reminder that temperature is not the sole determinant of human fate or suffering. And given the state of even the most generous estimates of global carbon budgets, it may have been already close to impossible to achieve when the target was formally enshrined in the Paris Agreement of 2015. Global emissions have only grown since, making the path to 1.5 degrees so treacherously steep, it’s not really a path but a crash. To give ourselves a two-thirds chance without relying on negative emissions would now require getting from 40 billion tons of annual carbon dioxide emissions to zero by 2030, which is one reason that many climate advocates will tell you that we should move on to more realistic targets, which might offer those working to build a climate-resilient world through adaptation a more useful set of expectations.
For planning purposes, of course, this is sound. If the climate has functionally retired the 1.5-degree goal, probably humans should, too. But if we are about to move beyond the target that has defined climate advocacy for nearly a decade, we should acknowledge not only what we’ve lost in missing it but also how much the target has helped us achieve. Because enshrining that goal — one so ambitious, it strained credibility — was nevertheless among the most consequential events of recent climate politics. Probably, I think, the most consequential.
The target was added to the Paris text, which already included the less ambitious goal of limiting warming to 2 degrees Celsius, on the basis of moral rather than practical argument, to acknowledge the cries from vulnerable and small-island nations that warming beyond 1.5 degrees represented, for them, genocide or death.
But it quickly came to serve a surprising technocratic purpose, too, by generating a universal base line against which even the most coolheaded climate observers might measure global progress (almost invariably finding it wanting).