In the first decade of the 21st century, most scientists and policy-makers were focused on 2°C as being the highest “safe” threshold for warming above pre-industrial levels. But emerging research was beginning to suggest that even this was too severe, threatening sea level rise that would wipe out low-lying islands. In response, some scientists began to investigate the benefits of keeping any temperature rise closer to 1.5°C. Armed with this research, the Alliance of Small Island States (AOSIS), a United Nations negotiating bloc, called for the adoption of a global target to limit warming to 1.5°C, warning that a 2°C warming limit “would devastate many small island developing countries”. James Fletcher, a UN negotiator for the AOSIS bloc at the 2015 UN COP climate summit in Paris, says it was an uphill battle to convince other countries to adopt this much tougher global goal. He recalls the head of a lower-income nation’s delegation cornering him at the end of a meeting in Paris: “He was wagging his finger in my face and saying, ‘You small island states will get 1.5°C over …