Science1 publisher2 min readPublished
Warming from 178 carbon majors persists to 2500 in a University of Washington model
A PLOS Climate study subtracts the top producers' emissions through 2024 from two runs of the FaIR model and finds their contribution to global temperature is about the same whether future emissions fall or keep climbing.
The Scientist · Science desk
What happened
- University of Washington researchers tested how long warming from the top 178 oil, gas, coal and cement producers lasts, and report that past emissions will keep affecting the climate for decades.
- The total temperature change traceable to the producers came out about the same in every scenario tested, including the most extreme one, where continued burning makes Earth much warmer.
- Even with emissions halted, the model keeps Earth at roughly 1.5 degrees Celsius above preindustrial temperatures.
Compiled by The ScientistSomething wrong?How this is made
Why it matters
- exposure If the degrees attributable to emissions already released hold steady across pathways, it is harder for a defendant to argue that whatever later emitters do dilutes its own contribution.
- capability A regulator weighing a permit now has a quantity for committed warming that does not require picking a future emissions pathway before the calculation can be done.
- constraint The result is a global temperature number, so linking a named company to a named disaster still depends on event attribution done case by case.
The design is a subtraction. Two model runs differ only in whether emissions from the carbon majors through 2024 are included, and the pair is repeated under a low-emissions and a higher-emissions scenario [3]. The 2024 cut-off means nothing sold or burned after this year counts toward the producers' contribution. That leaves 476 years of simulated climate after the last emission counted [17]. A substantial portion of the more than a trillion tons of carbon dioxide the carbon majors have emitted will stay in the air trapping heat for millennia [4].
Two of the results sound like they disagree. Where future emissions are limited, the 178 producers account for a larger percentage of warming above preindustrial levels [6]. In the most extreme scenario tested, future emissions account for a much larger percentage than the carbon majors do [7].
"The amount of warming is calculable and relatively independent of future emissions," said Dargan Frierson, the University of Washington associate professor of atmospheric and climate science who led the work [8].
The output is global mean temperature. Event-level attribution is separate work, and it is those event studies that the growing list of suits against major emitters has leaned on [13]. A plaintiff still needs that step; this paper supplies the persistence behind it. The summary released with the study did not include the carbon majors' contribution in degrees or an uncertainty range [18]. The approximately 1.5 C that Earth would hold above preindustrial temperatures even if emissions stopped is the total from all sources, not the 178 producers' share [5].
The university's summary says decades [1]. The paper itself is titled "Centuries of global heating from Carbon Majors: Dependence on future emissions pathways" [2], and the residence time of the gas it tracks runs to millennia [4]. Lauren Henrie, a former UW student of environmental science and resource management, is a co-author [16].
Existing litigation hinges on allegations that companies knew the risks and concealed them [14]. This study addresses a different period, in which emissions already released raise the odds of disasters that have not happened yet [15]. "If there are legal decisions about accountability, the responsibility is not just now, it will continue for many, many years into the future," Frierson said [9].
He put the forward-looking version plainly: "Future fossil fuel production will exacerbate climate disasters for many decades to come, so new legal battles about who is accountable should be expected for many years" [11].
What to watch
- Whether filings in pending climate suits start citing committed future warming from emissions already released, alongside event attribution.
- Whether other modelling groups reproduce the scenario-independence of the carbon majors' contribution using full coupled models instead of an impulse-response approach.
- Whether revisions to carbon majors accounting change the 178-producer roster or the trillion-ton total.