As carbon dioxide levels continue to rise in the atmosphere, the Earth is expected to become warmer. However, the exact amount of warming that will result from increased CO2 concentrations is still being studied. The relationship between CO2 and warming, known as climate sensitivity, will determine the future impact of rising CO2 levels on global temperatures. New research led by the University of Washington analyzes the most recent ice age to better understand this relationship between CO2 and global temperature, with a focus on narrowing the estimate of climate sensitivity to improve future warming projections.
The study, published in Science Advances, found that while most estimates for future warming remain unchanged, the absolute worst-case scenario is unlikely. The research indicates that the best-case scenario for doubling CO2 is about a 2-degree Celsius average temperature increase worldwide, while the most likely estimate is around 3 degrees Celsius. However, the worst-case scenario for doubling CO2 has been reduced by a full degree, from 5 degrees Celsius to 4 degrees Celsius. The current CO2 levels are at 425 ppm, heading towards double preindustrial levels by the end of the century unless emissions decrease.
The study focused on the Last Glacial Maximum, a period 21,000 years ago when Earth was on average 6 degrees Celsius cooler than today. Researchers used new statistical modeling techniques to assimilate paleoclimate records into computer models of Earth’s climate. By combining prehistoric climate records with computer simulations of the Last Glacial Maximum weather, the study revealed the role of CO2 in setting ice age temperatures. It was found that CO2 played a smaller role in ice age temperatures than previously estimated, leading to less dire predictions for warming from rising CO2 levels in the coming decades.
The authors caution against using recent decades as a good predictor of future global warming under the current trajectory of doubling CO2. Factors such as shorter-term climate cycles and the effects of atmospheric pollution make it difficult to rely on recent trends to predict the future. Instead, the study provides more confident predictions for the future by lowering the upper end of potential warming scenarios and suggesting that the most extreme warming outcomes are less likely. This new research provides valuable insights into the relationship between CO2 levels and global temperatures, contributing to more accurate future warming projections.
The findings of the study suggest that the recent past is not a reliable indicator of future global warming trends, as the spatial pattern of global warming seen in the last 40 years may not align with long-term patterns expected in the future. By focusing on the Last Glacial Maximum, researchers were able to gain a better understanding of historical temperature changes and the factors that influenced them. This knowledge allows for more informed predictions about future global warming and highlights the importance of taking into account historical climate data in climate models for more accurate projections.
In conclusion, the study by the University of Washington sheds light on the relationship between CO2 levels and global temperatures by examining the Last Glacial Maximum. By refining the estimate of climate sensitivity, the researchers were able to make more accurate future warming projections and reduce the likelihood of extreme warming scenarios. The findings provide valuable insights into the impact of rising CO2 levels on global temperatures and emphasize the importance of considering historical climate data in climate models to improve future predictions.
