A recent study from the University of Washington delves into historical climate data from the last ice age, a period when much of North America was encased in ice, to refine our understanding of CO2's impact on global temperature. The study reveals that the most catastrophic warming scenarios may be less likely than previously thought.
Published on April 17 in Science Advances, the research offers a fresh perspective by examining conditions during the Last Glacial Maximum, roughly 21,000 years ago, when the global average temperature was about 6 degrees Celsius cooler than today. At that time, atmospheric CO2 levels were significantly lower, around 190 parts per million, compared to today's 425 ppm.
"The core of our study is the refined estimation of climate sensitivity, which enhances our capacity to project future warming," stated Vince Cooper, a doctoral student at UW and the study's lead author. "By assessing the colder climate of the distant past, we gain insights into potential future warming under elevated greenhouse gas levels."
While the study maintains the established predictions for minimal and most probable warming scenarios upon CO2 doubling-around 2 and 3 degrees Celsius respectively-it adjusts the worst-case forecast down from 5 degrees to 4 degrees Celsius.
Researchers emphasize that recent climate trends are unreliable predictors of long-term global warming due to short-lived climate cycles and varying impacts of atmospheric pollutants. Instead, their findings hinge on ancient climate patterns derived from ice cores, ocean sediments, and fossilized pollen. These paleoclimate records were integrated with advanced computer models to reconstruct the Last Glacial Maximum's climate more accurately.
The study also considers the broader climatic impacts of the ancient ice sheets, which extended beyond simple reflection of solar radiation. By modifying atmospheric and oceanic currents, the ice sheets induced significant cooling effects, particularly over the northern Pacific and Atlantic oceans, which were further enhanced by cloud formations that increased solar reflectance.
Kyle Armour, a UW associate professor involved in the study, highlighted the implications of these findings: "This research allows us to make more confident predictions about future warming, particularly by lowering the likelihood of the most extreme scenarios. It doesn't alter the lower or most likely estimates, which are consistent with other evidence."
The new insights into climate sensitivity not only adjust our expectations for future warming but also underscore the nuanced role of CO2 in historical climate patterns.
Research Report:Last Glacial Maximum pattern effects reduce climate sensitivity estimates
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