Climate change: ’Stop using the worst-case scenario ... as the most likely outcome,’ experts say

Climate change: ’Stop using the worst-case scenario ... as the most likely outcome,’ experts say

31 January 2020 03:01 pm

By Doyle Rice

Scientific studies that use the worst-case, business-as-usual scenario for future levels of climate change are "misleading," experts claim.

"Stop using the worst-case scenario for climate warming as the most likely outcome – more-realistic baselines make for better policy," wrote climate scientists Zeke Hausfather and Glen Peters in a commentary in the British journal Nature that was published on Wednesday. 

According to the Intergovernmental Panel on Climate Change, the worst-case scenario predicts the globe will warm by 9 degrees Fahrenheit (5 degrees Celsius) by the end of the century. This is "a dystopian future that is fossil-fuel intensive and excludes any climate mitigation policies," the authors said.

"The high-emissions ... scenario – with its 500 percent increase in coal use by 2100 – is increasingly unlikely in a world of falling clean energy prices," tweeted Hausfather, a University of California, Berkeley, climate scientist. 

Rather than being seen as something that only had a 3 percent chance of becoming reality, it became known as the "business-as-usual" scenario by climate scientists and has been used in more than 2,000 research papers in recent years, the BBC said.

That scenario "was intended to explore an unlikely high-risk future ...The media then often amplifies this message, sometimes without communicating the nuances," the authors said in the Nature paper.

"That's not to say that these highest-end impacts are impossible to happen, but it is not business-as-usual," Peters, the research director at the Center for International Climate and Environmental Research (CICERO) in Oslo, Norway, told the BBC. "And that's the point we're really trying to make in this piece."

But this doesn't mean that human-caused climate change isn't going to cause big problems. "Assessment of current policies suggests that the world is on course for around 5.4 degrees Fahrenheit (3 degrees Celsius) of warming above pre-industrial levels by the end of the century – still a catastrophic outcome, but a long way from 9 degrees."

With 5.4 degrees of warming, "you're having a world where the coral reefs are largely wiped out're having a world where combined with deforestation, there's a real high risk of the Amazon rainforest turning into more of a savannah-type ecosystem in the long run," Hausfather told the BBC. 

Peters agreed, telling Mashable that 5.4 degrees of warming "will have catastrophic impacts for some, the loss of islands, corals, Arctic sea ice, some land glaciers, and not to mention changes in extreme weather.

"This is a world we want to avoid,"  he said. 

Still, the worst-case scenario may very well be off the table: "Happily – and that’s a word we climatologists rarely get to use – the world imagined (with 9 degrees of warming by 2100) is one that, in our view, becomes increasingly implausible with every passing year," Peters and Hausfather wrote in Nature. 

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