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Worst-case climate scenarios are no longer plausible

In order to explore and plan for possible climate futures, the scientific community uses various scenarios, or forecasts of how the future might evolve based on factors such as projected greenhouse gas emissions and different possible climate policies. While the Paris Climate Agreement’s goal was to limit global warming this century to two degrees Celsius above pre-industrial temperatures, some of the most pessimistic scenarios forecast temperatures rising by up to four or five degrees. 

However, a new study led by the University of Colorado Boulder (CU Boulder) suggests that such apocalyptic, worst-case scenarios are no longer possible, and that the goal set by the Paris Agreement may still be in reach.

The researchers compared a wide range of possible future climate scenarios developed by the Intergovernmental Panel on Climate Change (IPCC) to the projected 2005-2050 fossil fuel and industry greenhouse emissions growth rates that were most consistent with real-life observations from 2005-2020 and with 2050 projections of the International Energy Agency (IEA).

According to the scientists, from the 1,311 possible scenarios proposed by IPCC, only 100 to 500 were still plausible if current trends continue and countries adopt the climate policies they have already announced to reduce greenhouse emissions.

The most plausible climate scenarios project rises of temperature between two to three degrees Celsius above pre-industrial levels, with the most optimistic ones forecasting that warming may remain within the limits set by the Paris Agreement. 

“This is cautiously optimistic good news with respect to where the world is today, compared to where we thought we might be,” said study lead author Roger Pielke Jr., a professor of Environmental Studies at CU Boulder. “The two-degree target from Paris remains within reach.” 

According to Professor Pielke and his colleagues, relying on outdated or implausible scenarios has negative implications on how we think about, act, and spend money on climate change issues. 

“There’s a need for these scenarios to be updated more frequently. Researchers may be using a 2005 scenario, but we need a 2022 perspective,” said Professor Pielke. “You’re going to have better policies if you have a more accurate understanding of the problem, whatever the political implications are for one side or the other.” 

Although the findings appear to be quite optimistic, the scientists stress that two degrees of warming will still take a dramatic toll on the planet, and this is no time for complacency. “We’re getting close to our two-degree target, but we definitely have a lot more work to do if we’re going to get to 1.5,” said co-author Matthew Burgess, an assistant professor of Environmental Studies at CU Boulder.

The study is published in the journal Environmental Research Letters.

By Andrei Ionescu, Staff Writer

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