Climate change will progress more rapidly than previously thought, according to new research by Ivy Tan GRD ’16.
Tan’s study on the speed of progression of climate change was featured in the April edition of Science Magazine. Her research, which she carried out in conjunction with assistant professor Trude Storelvmo and lab researcher Mark Zelinka, was prompted by her priorresearch on the statistical relationships between mixed-phase clouds and aerosols through satellite observations.
Tan realized that modern climate models have underestimated how much ice is in mixed-phase clouds, leading to her discovery that climate sensitivity —the degree to which the atmosphere reacts to carbon dioxide— is actually somewhere between 5.0 and 5.3 degrees Celsius, rather than the previously believed 2.0 to 4.7 degrees Celsius.
“[The topic of the research is] at the heart of climate change right now,” Tan said. “Clouds are one of the leading uncertainties.”
Tan, who studies geology and geophysics at Yale, explained that levels of ice and liquid in mixed-phase clouds change as levels of CO2, a greenhouse gas, increase in the earth’s atmosphere. Storelvmo referred to this as an “intuitive process” through which ice clouds become liquid clouds, causing them to be more reflective than they were before. Most popular climate models, she said, have overestimated the amount of ice available to transform into liquid, which overestimates the cooling power of the clouds.
Simply, Zelinka said, clouds are not helping mitigate global warming and are increasing climate sensitivity.
Storelvmo stressed the importance of urgent action, encouraging citizens to adopt climate health as a cause rather than assuming an attitude of hopelessness.
“I hope that [the study] communicates a sense of urgency in terms of reducing emissions and reducing the amount of CO2 in the atmosphere,” Storelvmo said, “Because we now know we will have more warming for a given CO2 amount.”
In the study, the group looked at the Community Earth System Model from the National Center for Atmospheric Research, which is the most commonly accepted climate model, Storelvmo said. Zelinka noted that updating this particular model will have a strong effect on future model simulations.
Zelinka said the scientific community will now pay more attention to the issue of inaccuracies in climate models, as he believes a “striking” result such as this one calls for validation through repetition.
“I would anticipate that there will be other studies trying to do similar things to see if this is a robust result or a one-off thing,” Zelinka said.
Tan said that her work and that of other researchers in the field will likely lead to policy changes in the future.
She brought up another study, published by Nature in March 2016, which addressed a new climate model’s discovery that the West Antarctic Ice Sheet is not as stable as it was previously thought to be. Often overlooked details relating to changes in the atmosphere showed an expedited rate of water level rise, according to Tan. This finding, like Tan’s research, arose out of oversights of atmospheric processes that were more detailed than commonly understood.
Tan expressed disappointment, however, that landmark discoveries such as hers and that of the March 2016 Nature publication, which came to light in quick succession, were too late to factor into a recent monumental policy decision.
The U.N. announced on April 7 that more than 130 countries will sign the Paris Climate Deal on April 22 after deliberation at the 2015 United Nations Climate Change Conference in November and December of last year.