A UN climate report released Wednesday finds the globe will unavoidably slip past the Paris Climate Agreement’s 1.5-degree Celsius warming target in the next few years. The task now, the report states, is to make the period of warming “overshoot” as limited as possible, eventually bringing global average temperatures back down.
The annual UN Emissions Gap report is designed to inform decision makers headed into the next round of global climate talks in Turkey, known as COP31, next month. While past gap reports have expressed skepticism about meeting the 1.5-degree target, this one marks the first time that its authors have pronounced that missing the mark will be “imminent and unavoidable.”
“We are now saying this window has closed, but we can open it again by making the overshoot as brief as possible,” UN Environment Program Executive Director Inger Andersen said on a call with reporters. “This is about how to find a way back as shortly and as quickly as possible with as limited an overshoot as possible.”
Past reports have examined the distance between countries’ emissions reduction commitments and what it would take to limit global warming to 1.5 C above preindustrial levels.
However, this year’s report redefines the gap. Instead, it examines new emissions overshoot scenarios, and what it would take to limit peak warming to just 1.7 to 1.8 degrees C before bringing temperatures back down to 1.5 C through emissions cuts and the use of carbon removal technologies.
The report makes clear that every additional fraction of a degree of warming above 1.5 C “raises the risk of irreversible changes including in ice sheets, permafrost carbon, ocean circulation, and coral systems, along with devastating human impacts.”
Each added fraction of a degree of warming can have an “immense” impact “as measured in terms of damage, cost and loss of lives,” said climate scientist Michael Mann of the University of Pennsylvania. Mann was not involved in producing the UNEP report.
Emrah Gurel/AP
No upbeat scenario for overshoot
According to the UNEP, which is based in Nairobi, the lowest overshoot scenario would keep peak warming to between 1.7 and 1.8 degrees C and return global average temperatures to at or below 1.5 C by 2100.
However, to follow such a pathway, global greenhouse gas emissions would need to be slashed by far more than anything currently on the table at the upcoming COP31 talks. This would require an 18% cut by 2030, 45% by 2035, and 69% by 2040, relative to 2025 levels.
Meeting this lowest-possible overshoot scenario would require a tripling of renewable electricity capacity by 2035, and dramatic cuts to fossil fuels, including the phaseout of coal by 2040, the report states.
In addition, there would need to be a major scaling up of carbon removal technologies, which so far have not been proven to work at such a large scale.
In stark contrast to these figures, the fulfillment of existing emissions reduction pledges would only yield a 5-to-8% emissions cut by 2030 and an 11-to-15% reduction by 2035, the report found. This would be associated with a peak warming of about 2.6 degrees C.
If countries simply follow their current policies, then warming could reach a peak of about 2.8 C. That estimate has increased since last year, in part because of the withdrawal of the United States from the Paris Agreement and retraction of its emissions reduction commitments, the report states.
Even the scenario that assumes countries meet their existing reduction commitments, and nations with net-zero pledges succeed in fulfilling them, still brings warming to a peak of 2.1 C.
Gaby Oraa/Reuters/File
The bottom line
Clearly, overshooting 1.5 degrees C by the most limited amount possible and then coaxing temperatures back down over time is a tall order compared to what countries have pledged to do so far.
“Without urgent action, the lowest possible 1.5 C overshoot pathway will quickly fade,” the report warns. “Every five years of CO2 emissions at current levels pushes peak warming up by around 0.1 C.”
Mann said an additional 0.1 C of global warming “Permanently cuts global GDP by roughly 1.2% (over $1.2 trillion annually) and pushes approximately 140 million more people into life-threatening, dangerously hot climates.”
Overshooting the 1.5-degree target can be viewed as a milestone, but it doesn’t mean an absolute failure of climate science and policy, according to climate scientist Kate Marvel of Project Drawdown, a climate research and solutions nonprofit. Marvel was not involved in the UNEP report.
“There’s nothing special about any given temperature threshold,” she said. “The right unit isn’t degrees, it’s tons — of carbon dioxide, methane and other greenhouse gases. If we want to avoid the worst impacts, our task is and has always been to reduce these emissions as quickly as possible.”
“Passing 1.5 degrees is a sign that we’re not moving fast enough, but it doesn’t mean we’re doomed,” she said.
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