An upcoming report on ways to limit average global warming to 1.5°C has been generating a lot of discussion at this week’s climate negotiations in Bangkok, and in the weeks leading up to the meetings, with some climate policy advocates asking delegates to take the report seriously while others question its most basic scientific assumptions.
Drafts of the report by the Intergovernmental Panel on Climate Change (IPCC) have been leaking to media over the last eight months, with a version dated June 4 concluding that average global warming was on track to exceed the 1.5°C threshold by about 2040. It concluded that “governments can still cap temperatures below the strict 1.5°C (2.7°F) ceiling agreed in 2015 only with ‘rapid and far-reaching’ transitions in the world economy,” Reuters reported  at the time.
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The draft said average global temperatures are rising by about 0.2°C per decade, and that the difference between 1.5° and 2.0°C average warming will mean lower economic growth for developed and developing countries alike. Reuters cited impacts of floods, storm surges, droughts, and crop loss that will become significantly worse as global warming exceeds the 1.5°C guardrail .
Now, the report and its much-anticipated Summary for Policymakers is due to be finalized at a meeting in South Korea next month, in time to be presented at COP 24 in Katowice, Poland. “By nature, the findings of the IPCC will have significant impacts on governments’ climate policies and domestic implementation,” and on countries’ progression toward faster, deeper carbon cuts, notes ECO, the daily newsletter produced by Climate Action Network International during the Bangkok talks.
“While acknowledging that 1.5°C in itself entails significant climate change impacts already and requires enhanced adaptation resources for the poor,” ECO states, “these results include the limiting of global warming to 1.5°C, which is morally and ethically an imperative for the survival of entire nations, vulnerable communities, many ecosystems, and in reducing the risk of irreversible climate change impacts.”
Describing the 1.5°C report as “arguably the most important piece the IPCC has produced for a long time,” it urges Bangkok negotiators to “withstand the very likely attack by the usual suspects from countries in the hand of, or influenced by, powerful fossil fuel lobbies that will likely oppose crucial scientific results.”
But not everyone in the climate community is as taken with the IPCC’s findings. “The report will use unwisely low assumptions about the Earth’s climate sensitivity to pull a rabbit out of a hat: a carbon budget that from any sensible risk-management perspective simply does not exist,” Climate Code Red contends . “The political effect will be to say that the climate crisis is less bad than it is, and that we can ‘allow’ more fossil fuel emissions.”
In a detailed 1.5°C explainer issued last month, David Spratt of Australia’s Breakthrough National Centre for Climate Restoration says the final version of the IPCC report could come up with an even higher carbon budget than previous drafts. He called that possibility a “scandalous outcome that may finish the IPCC as a credible and dispassionate compiler of climate science research.”
He argues more broadly that IPCC reports “tend toward reticence and caution, erring on the side of ‘least drama’, exhibiting a preference for conservative projections and scholarly reticence, and downplaying the more extreme and more damaging outcomes, such that they are now becoming dangerously misleading with the acceleration of climate impacts globally.”
Spratt concludes that, from a “sensible risk management viewpoint”, there is no carbon budget left if humanity is to hit the 1.5°C long-term target. His post cites concerns about the “major tipping points” that might be crossed if average warming exceeds the threshold for any significant period of time, and points to “better farming techniques, regenerative agriculture, soil carbon and biochar, and technologies that can directly capture CO2 from the air”—but not the current “negative emissions” favourite, Biomass with Carbon Capture and Storage (BECCS)—as the best options to draw down the carbon dioxide already in the atmosphere.
The lead-up to the IPCC report has seen multiple studies addressing pathways to the 1.5°C target, or the severe added risks humanity will face at the margin between 1.5 and 2.0°. In one paper in the journal Nature Energy, a research team led by the UK’s Tyndall Centre for Climate Change Research concluded  that routine, day-to-day energy efficiency measures could play a major role in holding average global warming to 1.5°C and meeting many of the United Nations Sustainable Development Goals  (SDG) without resorting to the negative emissions technologies that feature prominently in more conventional 1.5° studies.