AI prediction: Limiting global warming to 1.5°C is "almost certainly" already out of reach 

Researchers have recently concluded that the global goal of limiting warming to 1.5 degrees Celsius above pre-industrial levels is now almost certainly out of reach. 

This stark finding suggests that the years ahead will almost inevitably break existing heat records – no matter how quickly greenhouse gas emissions decline.

The study, published in the journal Geophysical Research Letters, indicates a 50% chance that even if humanity achieves current targets for rapidly reducing greenhouse gas emissions to net-zero by the 2050s, global warming could breach two degrees Celsius above pre-industrial levels. 

Limiting global warming with decarbonization

Previous research, including assessments by the Intergovernmental Panel on Climate Change, had concluded that such decarbonization would likely keep warming below two degrees.

Noah Diffenbaugh, a climate scientist at the Stanford Doerr School of Sustainability, co-authored the study with Colorado State University climate scientist Elizabeth Barnes.

“We’ve been seeing accelerating impacts around the world in recent years, from heatwaves and heavy rainfall and other extremes,” said Diffenbaugh.

“This study suggests that, even in the best case scenario, we are very likely to experience conditions that are more severe than what we’ve been dealing with recently.”

Global warming beyond the 1.5-degree threshold

The new findings emphasize the speed at which the world is moving past critical warming goals. This year stands poised to surpass 2023 as Earth’s hottest year on record, with global average temperatures set to exceed 1.5 degrees Celsius (nearly 2.7 degrees Fahrenheit) above pre-industrial levels. 

According to the study, there is a nine-in-ten chance that the hottest year this century will be at least half a degree Celsius hotter – even if the world manages rapid decarbonization.

These alarming projections underscore that surpassing the 1.5-degree threshold is no longer a question of “if” but “when.” 

The significance is profound, given that this limit was a central target of the 2015 Paris Agreement, where nearly 200 nations pledged to keep warming “well below” two degrees while striving for 1.5 degrees. 

The study aligns with a growing body of evidence indicating that the 1.5-degree benchmark will be crossed, shifting the conversation toward how much hotter the planet will become.

Harnessing AI to fine-tune projections

For this research, Diffenbaugh and Barnes employed an innovative approach: they trained an AI system to forecast global temperatures under various emissions scenarios. 

The AI integrated temperature and greenhouse gas data from extensive climate model simulations and real historical temperatures. Armed with these inputs, it provided more refined projections than previously possible.

“AI is emerging as an incredibly powerful tool for reducing uncertainty in future projections. It learns from the many climate model simulations that already exist, but its predictions are then further refined by real-world observations,” said Barnes, a professor of atmospheric science at Colorado State.

This technique reduces uncertainty and hones in on more precise outcomes. By improving accuracy, policymakers gain a clearer understanding of the future they face, potentially guiding more informed decisions about mitigation and adaptation strategies.

Surpassing three degrees of warming 

A second paper by Barnes, Diffenbaugh, and co-author Sonia Seneviratne from ETH-Zurich suggests that many regions – including South Asia, the Mediterranean, Central Europe, and parts of sub-Saharan Africa – will surpass three degrees Celsius of warming by 2060 under scenarios of increasing emissions. 

The study, published in the journal Environmental Research Letters, notes that this warming may come sooner than previous models anticipated, indicating that some parts of the world face rapidly intensifying climate conditions.

The significance of surpassing such thresholds is immense. The consequences of even minor increases in temperature can cascade into extreme weather events, crop failures, water shortages, and heightened risks to human health and infrastructure.

Preparing for climate extremes

Both new studies build on earlier research by Diffenbaugh and Barnes that anticipated the timeline until warming goals are breached. However, rather than focusing solely on multi-year averages, the team shifted attention to the most extreme years and conditions. 

This perspective offers a glimpse into a future where temperatures and weather events are more volatile and challenging than the current average conditions can convey.

“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. 

This approach acknowledges that even meeting emissions targets may fail to shield humanity from extremes surpassing what we now experience.

For a scenario in which emissions are cut rapidly and reach net-zero in the 2050s – the most optimistic widely modeled scenario – there is a nine-in-ten chance that the hottest year this century will be at least 1.8 degrees Celsius hotter than pre-industrial times. 

Moreover, there is a two-in-three chance it will be at least 2.1 degrees hotter. If emissions remain too high to reach net-zero by 2100, a nine-in-ten chance emerges that the hottest year will be three degrees Celsius hotter. Under such circumstances, many regions could experience anomalies at least triple what occurred in 2023.

Adapting to a new normal

The projections highlight that even with robust decarbonization, the world must brace for greater extremes. Historically, climate policy and investment have prioritized mitigation – reducing carbon emissions – over adaptation, which focuses on reducing vulnerability to climate impacts. 

Decarbonization spending outpaces adaptation investments worldwide, as seen in policies like the 2022 Inflation Reduction Act in the United States.

“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 what they are currently prepared for,” Diffenbaugh warned.

Adapting to these changed conditions will be essential. Without measures to increase resilience – such as improved infrastructure, healthcare systems prepared for heat-related illnesses, agriculture tailored to new climate realities, and water resources managed to handle drought or flood – societies risk severe disruptions.

Beyond thresholds into severe climate extremes 

As the planet warms and thresholds are surpassed, scientists and policymakers alike must grapple with uncertainty. 

The research reveals a persistent gap between decarbonization goals and the severity of future extremes. 

Meanwhile, the AI-driven approach to refine climate projections may become a cornerstone of climate modeling, offering a more accurate and immediate window into what lies ahead.

The new knowledge that even optimistic emission scenarios may not prevent severe climate extremes underscores the importance of immediate and comprehensive action. 

Ensuring that investments in both mitigation and adaptation proceed in tandem could help protect human communities, ecosystems, and the global economy from the worst consequences of an increasingly warming world.

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