(Bloomberg) -- The battle to keep global warming within 1.5 degrees Celsius has been a rallying cry for climate action for nearly a decade. Now, with the planet almost certain to blow past the target, diplomats and campaigners at the COP29 summit have found themselves awkwardly clinging to a goal that no longer makes sense.
The evidence has become harder and harder to ignore. This year will once again be the hottest on record as greenhouse gas emissions continue to soar and Earth will likely register an average reading of 1.5C above pre-industrial levels for the first time. A study released this month using a new technique for measuring the rise in temperatures suggests the world was already 1.49C hotter at the end of 2023.
“1.5C has been deader than a doornail” for a while now, said Zeke Hausfather, a climate scientist at Berkeley Earth. Many of his peers agree. The United Nations has concluded that the world is on track to warm roughly 3.1C before the end of the century if nothing changes. That report was released just before representatives from nearly 200 countries gathered in Baku, Azerbaijan for the UN’s annual global climate conference, where they have been mired in bitter negotiations over how to raise money to help developing nations combat global warming.
The mood in Baku has not been hopeful. Leaders from most major economies, consumed by domestic political struggles, failed to turn up. The US, the world’s biggest economy and second-biggest polluter, is set to disengage from international climate cooperation under Donald Trump’s second term as president. And the host country’s president, Ilham Aliyev, has spent more time defending fossil fuels and picking fights with other countries than pushing for an ambitious deal.
Yet people at COP29 can’t stop talking about 1.5C. The number remains emblazoned on signs and leaflets all around, even if things look bleak. “Clearly, 1.5C is increasingly difficult,” Wopke Hoekstra, the European Union’s climate commissioner, told reporters before the start of summit. “No matter how difficult it is, I don’t want to give up on that goal, well knowing what the damage is that lies on the other end of that 1.5.”
It’s a common refrain and testament to how effective 1.5C has been as a tool for conveying the dangers of climate change. After countries agreed in the Paris Agreement to try and limit global warming to well below 2C, and ideally 1.5C, the UN asked the world’s top scientists to investigate the impacts of breaching both thresholds. The resulting special report, published in 2018, detailed how big a difference that half degree would make. A 1.5C world would see far lower sea level rise, fewer intense heat waves and other disasters than a 2C one.
This had a decidedly positive impact on climate action: Countries and companies increasingly put forward more aggressive climate targets, and started pouring money into renewables and green technologies. “It wasn’t that long ago that we were on a 3C, 4C degree sort of trajectory,” said Samantha Gross, energy security and climate initiative director at the Brookings Institution, “and now we’re not.”
The stakes are so high, and so much has been made of 1.5C, that backing away from the target risks taking the air out of the climate movement. “I don’t expect most governments or NGOs to acknowledge the reality of 1.5 anytime soon,” said David Victor, director of the Deep Decarbonization Initiative at the University of California at San Diego. “There’s no context out there where they can talk about things other than 1.5 and not be accused of backsliding.”
The big problem, climate science and policy experts say, is that no one knows what goal to embrace next. Should it be 1.6C, or 1.7C, or even higher? What is realistic but also still motivating? Should a new goal even be another temperature target or something else?
Billionaire climate investors have had their own takes. At COP28 last year, Bill Gates said realistically even 2C isn't that likely anymore, and the world should just be sure to stay below 3C. Australian mining magnate Andrew Forrest focuses less on warming and more on “real-zero” — meaning stopping emissions, not counterbalancing them — and says this should be the goal. “We’re seeing net-zero as a failure,” he said in an interview at COP29. “We’re seeing real-zero as something we can measure.”
Some politicians and experts have already begun to subtly shift how they talk about 1.5C. People are “more and more talking about how we can limit overshoot,” said Brown University climate scientist Kim Cobb. She’s referring to a somewhat complicated scientific theory — that there’s a possible future in which global warming exceeds 1.5C, but enough carbon emissions are removed from the atmosphere, through trees and carbon capture technology, to eventually cool the planet down again.
But overshooting and then returning to 1.5C isn’t the same as not breaching the limit in the first place. Research suggests that some of the impacts likely to occur at 1.5C and above, such as higher sea levels and species extinctions, won’t be reversed even if temperatures eventually go back down.
Several scientists have also expressed concern that passing 1.5C, even briefly, could lead to widespread public despair because of how much has been made of the consequences of failing to meet the target. That could be demoralize those in the climate fight, especially at a time when governments are already struggling to prioritize decarbonization while grappling with energy crises, inflation and backlash against policies that aim to phase out polluting consumer products such as gas stoves and diesel cars.
Currently, very few of the high-emitting countries that signed the Paris Agreement have either policies in place now or pledged climate goals for the next decade that align with the 1.5C target, according to the nonprofit Climate Action Tracker. Even Australia’s climate-forward Labor Party, which is bidding to host COP31 in 2026, has only put forward a 2030 carbon-reduction target that’s more consistent with a 1.6C or 1.7C world than a 1.5C one.
Next year’s COP30 meeting in Brazil will be a true test of the resilience of 1.5C as a North Star for global climate action. Countries are expected to turn up having set new emissions-cutting targets up to 2035. That means some of the world’s biggest polluters, including the US and China, will have to significantly step up their current climate ambition.
For the world’s most at-risk nations, abandoning the 1.5C goal is not an option. The annual COP meetings are their only opportunity to hold rich nations to account for the decades of pollution responsible for more extreme weather that now threatens their very existence. Including the 1.5C goal in the Paris Agreement was a major win for poor, climate-vulnerable countries and it remains a crucial instrument for them to press their case for more financial aid and urge large economies to take more aggressive steps to cut emissions.
Cedric Schuster, the Samoan minister who chairs the Alliance of Small Island States, is quick to point out that the world still hasn’t technically breached the Paris Agreement’s 1.5C target, which is based on the 20- to 30-year average of human-induced global warming.
“AOSIS finds it necessary to disabuse critics of this notion that 1.5C is dead,” he said in a press briefing in Baku. “With appropriate measures, 1.5C is still achievable. In this regard we must see countries rise to the occasion with new, highly ambitious” targets, he said.
Until a better totem emerges, the climate community seems determined to stick to the 1.5C talking point. It’s important to reckon with the usefulness of the goal, says Gross from the Brookings Institution. But she worries about the optics of doing it right now, when Trump’s re-election has already cast a shadow on prospects for progress.
“You don’t want it to look like Trump killed it,” she says. “Because he actually didn’t. It was already dead.”
--With assistance from Jennifer A Dlouhy and Akshat Rathi.
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