A new Stanford study found that even if we reach net zero emissions by 2100, global warming is on track to eclipse critical preventative goals set by the United Nations in the Paris Climate Agreement of 2015.
Researchers used artificial neural networks to predict the time until critical global warming thresholds are reached. The model projected that global warming would reach 1.5 degrees Celsius (2.7 degrees Fahrenheit) above pre-industrial levels between 2033 and 2035, consistent with existing assessments. Further, researchers found there is a substantial likelihood of exceeding the 2 degrees Celsius threshold even if significant emissions reductions are implemented.
The AI model uses historical temperature data and climate simulations as inputs. This unique approach allows the machine learning model to make more accurate predictions beyond the scope of historical data, according to Noah Diffenbaugh, the study’s lead author and Stanford professor of earth systems. Further, they say the AI could separate signal from noise and directly incorporate uncertainties into the prediction.
The study’s results put into question the hopes of the Paris Agreement to “[hold] the increase in the global average temperature to well below 2 degrees Celsius above pre-industrial levels and pursuing efforts to limit the temperature increase to 1.5 degrees Celsius above pre-industrial levels, recognizing that this would significantly reduce the risks and impacts of climate change.”
“The main message from the AI prediction [is] that the world’s on the cusp of reaching 1.5 degrees of warming,” said Diffenbaugh. “The AI predicts a high probability [of reaching 1.5 degrees] in the next 10 to 15 years, even if emissions are reduced in that time period.”
So far, average global temperatures have warmed 1.1 degrees Celsius above pre-industrial levels. With global emissions continuing to rise, temperatures will almost certainly be driven closer to the 1.5 degree threshold, according to Diffenbaugh.
Visiting climate scientist from Cornell University Douglas MacMartin put this number into context. MacMartin was not a part of the Stanford study.
“If 1.5 degrees warmer is the global average, land temperatures are rising about twice as fast and arctic temperatures are rising maybe four times as fast,” MacMartin said. “Now you’re melting large amounts of ice and raising risks for the future.”
California has already seen significant climate change. At 1.5 degrees of warming, experts warn weather conditions will become increasingly unpredictable.
“We’re already living in an era of climate change in California, and we have high confidence that those changes will intensify,” Diffenbaugh said. “We’re more likely to have intense heat waves, extreme wildfire weather, early melting snowpack and the water deficits that are associated with that.”
As current climate trends continue, record breaking heatwaves hotter than those in Sept. 2022 may become the norm. Wetter conditions may also persist. This year, there have been record quantities of rain in short periods — leading to the return of Lake Lagunita on campus — due to a weather phenomenon known as an atmospheric river that is linked with climate change, according to professor of interdisciplinary environmental studies and Director of Woods Institute Chris Field
Along with increasingly variable weather patterns, 1.5 degrees of warming will also result in critical losses to the natural world.
“Cold water coral reefs pretty much completely disappear,” Field said.
Beyond the direct impacts from 1.5 degrees of warming, further temperature increases can lead to a cycle of worsening climate. Once global warming reaches beyond 2 degrees, vicious cycles become virtually unstoppable, experts warn. Even if emissions from human activities are kept at zero, there remain massive emissions of greenhouse gasses from ecosystems, according to Field.
“We’re looking at increasing risk of vicious cycle activities, starting out in the natural world where no matter what we do to cut emissions, we see greenhouse gas emissions from burning forests in the Amazon or from melting permafrost at high latitudes,” Field said. “Minimizing the risk of some of these vicious cycle feedbacks is really important. 1.5 [degrees Celsius] provides a pretty high level of safety that 2 [degrees Celsius] clearly does not.”
However, if net zero climate pledges are met, Earth may not enter the 2 degrees Celsius temperature rise scenario.
“For 2 degrees, there have been a lot of pledges that have been made by countries, by states, by institutions including Stanford, for net zero,” Diffenbaugh said. “The AI prediction suggests that those [pledges] may be needed to avoid 2 degrees.”