For decades, the international community considered 2°C of warming above pre-industrial levels as the upper limit of “safe” global temperature rise. However, growing scientific evidence in the early 2000s demonstrated even that threshold posed catastrophic risks, particularly for low-lying island nations threatened by accelerating sea-level rise. This realization spurred a shift toward the more ambitious goal of limiting warming to 1.5°C.
The Fight for Lower Warming Limits
The Alliance of Small Island States (AOSIS) led the charge, advocating for the 1.5°C target at the 2015 United Nations Climate Change Conference (COP) in Paris. Their argument was stark: a 2°C increase would be devastating for vulnerable island nations. Negotiator James Fletcher recalls fierce resistance, with some countries vehemently opposing the stricter target. He recalls one delegate threatening that the 1.5°C goal would only be achieved “over their dead body.”
Despite the opposition, the 1.5°C target secured a place in the landmark Paris Agreement. This was due to pressure from the European Union, behind-the-scenes support from the United States, and even an intervention from Pope Francis. The inclusion of the 1.5°C goal was not based on a fully-defined understanding of its implications; rather, it was a leap of faith that prompted further scientific investigation.
Scientific Validation and Global Adoption
In 2018, the Intergovernmental Panel on Climate Change (IPCC) published a special report on the 1.5°C target, confirming the significant benefits of limiting warming to the lower level. The report solidified the goal as a global imperative, aligning it with the need to achieve net-zero emissions by 2050.
This target quickly became a focal point for governments and corporations worldwide. Some nations, including the UK, revised their national climate goals to align with the more aggressive 1.5°C trajectory. Climate scientist Piers Forster credits the target for driving nations to commit to tougher reductions than they would have otherwise considered.
A Mixed Legacy, but Lasting Impact
Despite the momentum, global temperatures continue to rise, and emissions cuts fall far short of what is required to meet the 1.5°C target. Current projections suggest the world will surpass this threshold within a few years. However, the goal remains central to measuring progress in reducing emissions.
The 1.5°C target fundamentally altered the climate debate. What was once considered an ambitious extreme has now become the benchmark against which all climate action is measured. The idea that 2°C was ever a “safe” warming limit now appears dangerously complacent.
The 1.5°C target’s legacy is not about its immediate success, but its lasting impact: it shifted the focus to every fraction of a degree and cemented the urgency of climate action in the minds of policymakers and the public alike.
