UN accepts overshooting 1.5C warming limit – at least temporarily – is “inevitable”

The head of the United Nations has conceded that the global average temperature will rise by more than 1.5C above pre-industrial levels, breaching a key limit set in the 2015 Paris climate agreement.

In a video message commenting on a new UN report on the gap between national plans to cut emissions and what is needed to meet global climate goals, António Guterres said “scientists tell us that a temporary overshoot above 1.5 degrees is now inevitable – starting, at the latest, in the early 2030s”.

The 1.5C threshold is symbolically important, as all governments agreed in the Paris climate accord to try to limit global warming to that level. Since then, diplomats at climate talks have described the temperature goal as the world’s “North Star” and pledged to “keep 1.5 alive”.

In May, however, scientists with the World Meteorological Organization predicted there was a 70% chance that the 2025-2029 period will be more than 1.5C hotter than pre-industrial times and said only a “fortuitous intervention of natural climate variability” like a volcanic eruption could prevent the 1.5C limit being breached in the longer term.

Guterres’ reflections on the emissions gap report are the first time the UN has formally accepted that the 1.5C limit will definitely be breached. The report finds that “the multi-decadal average of global temperature will now exceed 1.5C, very likely within the next decade.”

Rachel Cleetus, a senior policy director at the nonprofit Union of Concerned Scientists, said the report’s findings were “alarming, enraging and heart-breaking”, adding that “years of grossly insufficient action from richer nations and continued climate deception and obstruction by fossil fuel interests are directly responsible for bringing us here”.

Hopes for return to 1.5C

The UN’s rhetoric has now shifted to bringing the temperature back down below 1.5C as quickly as possible within this century. It says this can be done by reaching global net zero and then net negative emissions, whereby the world absorbs more greenhouse gas than it produces using natural sinks like forests or carbon removal technologies.

Guterres said breaching the 1.5C limit was “no reason to surrender. It’s a reason to step up and speed up. 1.5C by the end of the century remains our North Star. And the science is clear: this goal is still within reach. But only if we meaningfully increase our ambition.”

The head of the UN’s climate arm, Simon Stiell, said last week that “temperatures absolutely can and must be brought back down to 1.5C as quickly as possible after any temporary overshoot, by substantially stepping up the pace on all fronts.”

Last year’s Emissions Gap Report measured the “likelihood of warming exceeding a specific temperature limit”. This year’s report changed this to the “likelihood of limiting warming below a specific temperature limit over the 21st century”.

The report found that even in the most ambitious scenario – where governments’ NDC climate plans and net-zero pledges are achieved in full – there is only a one-in-five chance of limiting global warming to 1.5C in this century.

If governments continue with their current policies rather than strengthening them to meet their climate targets, the likelihood of limiting global warming to 1.5C this century drops to 0% and to 2C to just 8%. The report noted that for the G20 group of big economies, implementation of policies to meet net zero targets “remains generally weak”.

Net-negative emissions goals

While most governments have targets to reach net zero, few have net negative goals. Finland plans to reach net netagive by 2040, Sweden by 2045, Denmark aims for a 110% cut in emissions by 2050 while Germany aims to reach net negative by 2060.

The German government argues that net-negative emissions will be necessary in some countries to balance out others’ continued emissions and to cancel out greenhouse gas emissions that can’t be avoided, like methane from farming.

Denmark is investing in direct air capture machines to suck carbon dioxide out of the atmosphere and in paying fossil fuel companies to store the gas under the seabed, where it does not contribute to climate change.

Some heavily-forested countries like Guyana claim to be net negative already, although Guyana’s argument rests on forestry accounting methods criticised by some scientists.

The Emissions Gap Report’s authors said that the faster net zero is reached, the cheaper it will be to get the temperature back down to 1.5C. “Each year of inaction makes the path to net zero by 2050 and net-negative emissions thereafter steeper, more expensive and more disruptive,” they warned.

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