In the first decade of the 21st century, most scientists and policymakers focused on 2°C as the highest “safe” limit for warming above pre-industrial levels. But emerging research began to suggest that even this was too serious, threatening to raise sea levels that would destroy the low-lying islands. In response, some scientists began to examine the benefits of keeping any increase in temperature closer to 1.5°C.
Armed with this research, the Alliance of Small Island States (AOSIS), a UN negotiating bloc, called for the adoption of a global target to limit warming to 1.5°C and warned that limiting warming to 2°C”would devastate many small island developing countries“.
James FletcherUN negotiator for the AOSIS bloc at the UN COP climate summit in Paris in 2015, says it has been an uphill battle to convince other countries to adopt this much tougher global target. He recalls being cornered by the head of a lower-income nation’s delegation at the end of a meeting in Paris: “He was waving his finger in my face and saying, ‘You little island nations are going to get 1.5C on my dead body’. That’s how angry they were.”
With the help of pressure from the European Union, tacit support from the US and even the intervention of Pope Francis, 1.5°C made it into the hugely influential Paris Agreement of 2015. Without a formal assessment of what 1.5°C warming would actually mean for the planet, the world’s climatologists went to work.
In 2018, the Intergovernmental Panel on Climate Change published its news on the 1.5°C target, confirming the relative benefits of keeping warming at a lower level and crystallising a new global goal of achieving net zero emissions by 2050 in line with the 1.5°C trajectory.
Both targets quickly became a rallying cry for governments and companies around the world, and some countries, including the UK, updated their national climate targets to align with the new, tougher target.
Piers Forster at the University of Leeds in the UK, credits the 1.5°C target with helping to push countries to commit to much tougher climate targets than they might have previously considered. “I think it created a sense of urgency,” he says.
The target’s legacy is mixed. Despite the fanfare, global temperatures are still rising and the world has delivered nothing like the emissions reductions needed to meet the 1.5°C pledge. The best scientific assessments now project that the world will cross the warming threshold within a few years.
However, 1.5°C remains the central climate target against which global progress in reducing emissions is measured. The public and policy makers are now much more focused on every fraction of a degree of temperature increase. “Exceeding” 1.5°C is widely seen as a risky future, and the idea that 2°C was ever considered a “safe” limit for warming seems ludicrous.
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