Early Draft of UN Report Sees Radical Action, Dramatic Trade-Offs on Road to 1.5°C Future
Humanity will need “radical action”, dramatic trade-offs, and a certain amount of luck to keep average global warming at 1.5°C over the long term—and even that target will carry serious impacts, according to an early draft of a major United Nations panel report that is due to be finalized in September, but was obtained and published this week by Climate Home News.
Like the UN itself, Climate Home stresses that the findings “may change substantially” by the time the report is finalized, particularly because the May 15 deadline for incorporating new science in the analysis is still three months away. Still, the report underscores the depth of the decarbonization challenge and the massive scope and variety of activity required to meet it.
Like this story? Subscribe to The Energy Mix and never miss an edition of our free e-digest.
The draft states that the world as a whole will likely exceed the 1.5°C threshold in the 2040s, and Climate Home notes that the UK Met Office “sees a one in 10 chance the global average will flicker over 1.5°C within five years”. Even at that threshold, the draft report states, “tropical reefs are at ‘high risk’ of no longer being dominated by corals. The Arctic could become nearly ice-free in September. There will be ‘fundamental changes in ocean chemistry’ that could take millennia to reverse.”
But the more conventional target of 2.0°C average global warming is riskier still. “The next half-degree ramps up the risk of flood, drought, water scarcity, and intense tropical storms. There are knock-on effects: reduced crop yields, species extinction, and transmission of infectious diseases like malaria. And these pressures multiply the threat of hunger, migration, and conflict.”
2.0°C also translates into 10 centimetres of additional sea level rise compared to 1.5, and “raises the risk of the Greenland and West Antarctic ice sheets collapsing over the long term, dooming future generations to multi-metre sea level rise.”
Either way, poor and coastal communities will be hardest hit. “Vulnerable communities are already experiencing threats from climate change,” Climate Home notes. “At both 1.5°C and 2.0°C, these effects scale up. When crops fail, smallhold farmers may lose their livelihoods and be compelled to leave their homes, while the urban poor suffer from food price spikes.”
From that starting point, the report calls for rapid, deep emission cuts that have “no documented historic precedents”, apart from the recent transformation of global electricity markets. Shifting far enough, fast enough will “require more planning, coordination, and disruptive innovation across actors and scales of governance than the spontaneous or coincidental changes observed in the past”.
And even then, every available pathway to 1.5°C relies on removing 380 to 1130 gigatonnes of carbon dioxide from the atmosphere. “Firstly, this is to cancel out the leftover emissions after everything that can be cut has been cut,” Climate Home explains. “Secondly, it makes up for overshooting the emissions limits that would keep temperatures below 1.5C.”
After that, the draft contends that a 1.5°C future will depend on a certain degree of luck—and on carbon capture or afforestation strategies that trade off against other global objectives.
“Scaling up negative emissions in line with the 1.5°C goal may clash with efforts to end hunger,” Climate Home notes. And even then, “there is a high chance that the levels of CO2 removal implied in the scenarios might not be feasible due the required scale and speed of deployment required and trade-offs with sustainable development objectives,” the draft acknowledges.