Groundbreaking AI-powered climate projections reveal that even rapid emissions cuts won't prevent record-breaking heat, underscoring the urgent need for adaptation investments.
Research Letter: Data-Driven Predictions of Peak Warming Under Rapid Decarbonization. Image Credit: Guenter Albers / Shutterstock
A new study has found that the global goal of limiting warming to 1.5 degrees Celsius above pre-industrial levels is now "virtually certain" to be out of reach.
The results, published Dec. 10 in Geophysical Research Letters, suggest the hottest years ahead will likely shatter existing heat records. The authors reported a 50% chance (even odds) that global warming will breach 2 degrees Celsius even if humanity meets current goals of rapidly reducing greenhouse gas emissions to net zero by the 2050s.
A number of previous studies, including the authoritative assessments by the Intergovernmental Panel on Climate Change, have concluded that decarbonization at this pace would likely keep global warming below 2 degrees.
"We've been seeing accelerating impacts around the world in recent years, from heatwaves and heavy rainfall and other extremes. This study suggests that, even in the best-case scenario, we are very likely to experience conditions that are more severe than what recent averages indicate," said Stanford Doerr School of Sustainability climate scientist Noah Diffenbaugh, who co-authored the study with Colorado State University climate scientist Elizabeth Barnes.
This year is set to beat 2023 as Earth's hottest year on record, with global average temperatures expected to exceed the 1.5 degrees Celsius threshold (or nearly 2.7 degrees Fahrenheit) above the pre-industrial baseline before people started burning fossil fuels widely to power industry. According to the new study, there is a 90% likelihood that this century's hottest year will be at least 0.5°C hotter than 2023, even under rapid decarbonization.
AI's Role in Climate Projections
For the new study, Diffenbaugh and Barnes trained an advanced convolutional neural network (CNN) to predict how high global temperatures could climb, depending on the pace of decarbonization.
When training the AI, the researchers used temperature and greenhouse gas data from vast archives of climate model simulations. However, to predict future warming, they gave the AI the actual historical temperatures as input, along with several widely used scenarios for future greenhouse gas emissions.
"AI is emerging as a potent tool for reducing uncertainty in future projections. Our CNN model refines existing climate projections by learning from vast data sources and real-world observations," said Barnes, a professor of atmospheric science at Colorado State.
The study adds to a growing body of research indicating that the world has almost certainly missed its chance to achieve the more ambitious goal of the 2015 Paris Climate Agreement, in which nearly 200 nations pledged to keep long-term warming "well below" 2 degrees while pursuing efforts to avoid 1.5 degrees.
A second new paper from Barnes and Diffenbaugh, published Dec. 10 in Environmental Research Letters with co-author Sonia Seneviratne of ETH-Zurich, suggests that many regions, including South Asia, the Mediterranean, Central Europe, and parts of sub-Saharan Africa, will surpass 3 degrees Celsius of warming by 2060 in a scenario in which emissions continue to increase—sooner than anticipated in earlier studies.
Extremes Matter
Both new studies build on earlier 2023 research in which Diffenbaugh and Barnes predicted the years remaining until the 1.5 and 2 degrees Celsius goals are breached. However, because these thresholds are based on multi-year averages, they don't tell the whole story of how extreme the climate could become.
"As we watched these severe impacts year after year, we became more and more interested in predicting how extreme the climate could get even if the world is fully successful at rapidly reducing emissions," said Diffenbaugh, the Kara J Foundation Professor and Kimmelman Family Senior Fellow at Stanford.
For a scenario in which emissions reach net zero in the 2050s—the most optimistic scenario widely used in climate modeling—the researchers found a 90% chance that the hottest year this century will be at least 1.8°C hotter globally than the pre-industrial baseline, with a two-in-three chance for at least 2.1°C.
In a scenario in which emissions decline too slowly to reach net zero by 2100, Diffenbaugh and Barnes found a 90% likelihood that the hottest year will be 3°C hotter globally than the pre-industrial baseline. In this scenario, many regions could experience temperature anomalies at least triple those of 2023.
Investing in Adaptation
The new predictions underline the importance of investing in decarbonization and measures to make human and natural systems more resilient to intensified climate extremes such as severe heat, drought, and heavy precipitation. Historically, those efforts have taken a back seat to reducing carbon emissions, with decarbonization investments far outstripping adaptation spending in global climate finance and policies such as the 2022 Inflation Reduction Act.
"Our results suggest that even if all the effort and investment in decarbonization is as successful as possible, there is a real risk that, without commensurate investments in adaptation, people and ecosystems will be exposed to climate conditions that are much more extreme than existing systems are equipped to handle," Diffenbaugh said.
Diffenbaugh is a professor of Earth system science at the Stanford Doerr School of Sustainability and a senior fellow at the Stanford Woods Institute for the Environment.
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