It does not sound like much: 0.5 degrees. Yet on many of the most crucial measures of the climate crisis, the difference between a global temperature rise of 1.5 degrees above pre-industrial levels and one of 2 degrees is vast.
According to the Intergovernmental Panel on Climate Change (IPCC) in 2018, it is the difference between 14% of the world’s population being exposed to extreme heat waves at least once every five years, and 37%; between 6% of insects losing over half of their viable habitats, and 18%; between 70-90% of coral reefs dying out, and 99% of them; between one ice-free summer in the Arctic every century, and one every decade.
It is in the range between 1.5 degrees and 2 degrees that many of the unstoppable feedback loops, such as the additional heating resulting from a mostly or entirely ice-free Arctic, that most concern climate scientists kick in. Beyond 2 degrees, all of these measures accelerate further still.
The IPCC’s latest estimate suggests that the world is currently on track to pass 1.5 degrees in the 2030s or 2040s, and reach a cataclysmic temperature rise of 2.7 degrees by the end of the century. That, in essence, is the fundamental fact of the COP26 climate summit, which begins in Glasgow on Sunday 31 October.
Conference of the parties summits have taken place every year for the past 26 years, apart from last year when it was postponed due to the pandemic. Yet this year’s will be the most significant since the Paris summit in 2015. As Philippa Nuttall, our environment and sustainability editor, describes in this very useful COP26 explainer, it was at Paris that governments agreed to keep global temperature rises below 2 degrees and to strive to limit them to 1.5 degrees – and to come forward every five years with new, stricter goals bringing the world closer to a pathway to 1.5 degree rises.
Due to last year’s postponement, the first such crucial update is due at this year’s gathering, which runs over the next two weeks to Friday 12 November. For more on country-by-country emissions and commitments, explore all the data on our emissions tracker.
As Philippa writes, there are six key areas where progress at the summit is essential: the new national emissions reductions goals; financial support for poorer countries; compensation for countries most affected by climate change; carbon trading; methane emissions; and nature-based solutions to slow temperature rises.
It is far from certain how much the summit will deliver. None of the leaders of China, Russia or Brazil will be attending and doubts loom over how far Joe Biden is willing to go to step up America’s efforts. As I write in my column this week, the low-trust environment between and within countries gives grounds for pessimism. In any case, it will be a crucial and potentially dramatic couple of weeks for humanity’s future.