In his “Discourses on Livy,” fifteenth-century philosopher Niccolo Machiavelli writes, “It is easy, by diligent study of the past, to foresee what is likely to happen in the future.” Geology and geophysics professor Alexey Fedorov argues that this statement applies to climate patterns as well.
In his most recent research paper, published in the journal Science, Fedorov and his co-authors claim that analyzing ocean temperatures of the Pliocene era will reveal information about climate change patterns of the future. The Pliocene era, a geological period that occurred five million years ago, was the last time period before the present during which atmospheric carbon dioxide levels reached the level of 400 parts per million.
George Mason University professor Natalie Burls, a study co-author, said that climate reconstructions of the Pliocene suggest that global warming tends to be “polar amplified,” or that more warming occurs in the temperate regions than in the tropics. She also said that the east-west sea surface temperature gradient within the tropical Pacific should decrease at a rate similar to the rate at which the north-south sea surface temperature gradient decreases. In other words, the rate at which change in sea temperature decreases should be similar along the lines of latitude as it is along the lines of longitude.
“This insight has important implications for how we might expect large-scale atmospheric circulation and precipitation patterns in the tropics — the Walker circulation — as well as El Nino-related variability to change with global warming,” Burls wrote in a Wednesday email to the News.
Heather Ford, co-author of the paper and a postdoctoral research scientist at Columbia University, said that sea surface temperatures reveal information about global climate patterns because they show how heat is stored and transported in the ocean. She added that this data also demonstrates how heat is exchanged between the ocean and the atmosphere, which is important to understanding warm climate states.
According to Ford, 90 percent of the global energy due to global warming is currently being absorbed by the ocean. Ford added that studying the Pliocene is more useful in understanding long-term consequences of climate change than more immediate climate change patterns over the next century.
“The climate change we can expect in the next century or less will be rapid and extreme as the global climate system adjusts to the high levels of carbon dioxide,” she said.
Burls said that the next step in her research with Fedorov is trying to improve the climate model simulations to better understand how scientists can use the reconstructed data from the Pliocene era to predict the climate patterns of the future. Currently, models with elevated carbon dioxide levels show extra-tropical warming that falls short of the much more significant change seen in the data from the Pliocene. However, when one makes simulations with hypothetical modifications to the reflection of sunlight by clouds, the model reproduces sea surface temperature changes that are consistent with the reconstructed data.
“This suggests that the models may be missing key cloud feedbacks in response to carbon dioxide-induced warming or alternatively that atmospheric aerosol concentrations during the Pliocene supported the required changes in cloud reflective properties,” Burls said.
The Pliocene era had sea surface temperatures of more than 3 degrees Celsius higher than today.