UN says global warming will cross 1.5 deg C soon, hit at least 1.8 deg C

SINCE countries signed onto the 2015 Paris Agreement, the United Nations has regularly reported on the world’s progress at limiting global warming to 1.5 deg C above pre-industrial levels. A landmark UN report published today (Sep 2) brings an end to that era — and the beginning of a new one. 

The world will likely surpass 1.5 deg C in the next few years, it says, and warming will peak at around 1.8 deg C in the best-case scenario, or at roughly 2.6 deg C under current policies. (Currently, long-term warming stands at 1.4 deg C with occasional short-term spikes above that.)

Since so-called “overshoot” is virtually guaranteed, the goal must become “overshoot, peak and decline” — that is, putting climate change in reverse, ideally by the end of this century. 

“We are at a really critical point,” said Debra Roberts, honorary professor at the University of KwaZulu-Natal in South Africa and a co-author of the UN Environment Programme (UNEP) report, titled Limiting Overshoot. “The level of ambition [of countries] will really determine whether overshoot lasts for decades or lasts for millennia.” 

Lowering the planet’s temperature will require quickly cutting greenhouse gas pollution from fossil fuels as well as drawing carbon dioxide out of the atmosphere, via natural means (such as reforestation) and technological ones like direct air capture. 

For warming to drop back under 1.5 deg C, countries will not only have to cancel out their emissions but push them into a net negative range.

At the same time, they’ll need to ensure that communities and economies can adapt to climate impacts that are becoming more severe. The report notes that while reducing the temperature would curtail dangers, some impacts, such as sea-level rise or biodiversity loss, may be irreversible.

Every fraction of a degree of warming brings higher risks and more intense impacts.

Rescuers in Nepal and China are still searching for about 4,000 missing people — with more than 1,000 known dead — after a glacial collapse caused devastating flooding.

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Five heat waves descended on Europe this summer, leaving rivers parched and crops withered; they have been linked to tens of thousands of excess deaths.

Wildfires filled the air with soot across North America and South-east Asia. In coming decades, the report warns, island nations face potential submersion, critical ocean currents may weaken and health risks will rise. 

Limiting Overshoot is the first major UN climate review to assume the breaching of 1.5 deg C and offer a pathway for how to return to it.

Countries have made some progress on slowing climate change, the authors note. Emissions have nearly plateaued in recent years. But they would need to nearly halve by 2030 and effectively hit zero by mid-century to keep the world below 1.5 deg C. 

Overshoot will make it impossible to avoid reliance on carbon dioxide removal: The world will now need to lower the CO2 level in the atmosphere rather than just keep it from rising. But experts stress that it’s not a silver bullet and cutting fossil-fuel use is still imperative. 

“We cannot rely on CDR as a get-out-of-jail-free card, if you like,” said Richard Betts, a climate scientist at the University of Exeter and the UK Met Office and a report co-author. “We have to reduce emissions with even more urgency than before.” 

Cutting and halting emissions — or mitigating — climate change and adapting to it are both essential and are mutually reinforcing, the authors write.

Adaptation will go more smoothly, and there will be more resources available for it, if communities are not fighting ever-worsening and more frequent disasters because emissions remain high. 

The authors are clear where the burden of leadership falls. “Countries with a greater historical responsibility for climate change should do the most work,” said Inger Andersen, executive director of UNEP. The US is the biggest cumulative emitter. 

Absent from the report is significant discussion of a role for unproven geoengineering techniques, such as seeding the upper atmosphere with sunlight-reflecting chemicals or brightening clouds above oceans by spraying seawater into the air. 

“The science around this is only just beginning,” Andersen said. “So this is not a place where we can hang our hat, as solutions.” BLOOMBERG