By Kala Hunter
Medill Reports
How sensitive is the climate? This is the question that prompted marine and geochemist Alan Seltzer, a Ph.D. assistant scientist at Woods Hole Oceanographic Institution, and climate scientists from Scripps Institution of Oceanography to look at land temperatures at the end of the last ice age.
While computational models have long existed to help unveil temperatures from the past, gathering physical data is more favorable for its precision. Until Seltzer and a team of scientists from Scripps released their findings in a study in May 2021, there wasn’t a consensus as to how much the cooled during the last ice age 20,000 years ago nor why the land warmed more than the ocean.
“The climate actually changed a lot more than people were saying during the last ice age, which means it could change a lot more in the future with warming,” said geoscientist Jeff Severinghaus, a professor at Scripps and co-author of the study.
He reported the findings at this year’s annual fall Comer Climate Conference. The Conference draws international climate experts to share their latest research. The data from past climate events helps scientists identify the accelerating pace of climate change now.
The team used noble gases in ancient groundwater at low latitudes across six continents to fill a knowledge gap about land temperatures during the Last Glacial Maximum (LGM). Noble gases are inert and stay put, even when the climate changes.
“The ice age was 6 degrees cooler than we (scientists) thought,” Severinghaus said. “This will stand the test of time.”
Seltzer and the research team went to artisan aquifers in understudied, low-elevation and low-latitude regions of Brazil, Vietnam, India, Australia and parts of Africa. They combined research in some of these areas over four decades to find water that collected up to 20,000 years ago. Notably, this study includes previously unreported noble gas data from groundwater samples collected in the mid-1990s in Australia and Vietnam, and between 2008 and 2010 in India. The noble gases were part of the puzzle. Soil temperature was the other piece of the puzzle. Soil temperature can be very similar to surface temperature.
“If you go to an ancient aquifer that has remained sealed away from the atmosphere and measure the krypton and xenon concentrations, you can measure the temperature at the time the rain fell,” Severinghaus said.
Seltzer and the team found these low-latitude locations cooled by 6 degrees Celsius (10.8 degrees Fahrenheit). The land temperature will warm 50% more than the ocean. These new findings paint a sobering for picture for future warming. This revelation during the LGM will help predict the scale of future warming fueled by present-day climate changes.
“By demonstrating (the climate sensitivity during the LGM), it confirms that there will be more extreme floods and extreme drought,” glaciologist Richard Alley of Pennsylvania State University said.
“It is understood that land gets hotter than the ocean, but now thanks to this study we can predict this with physical modeling instead of computational modeling,” Alley said.
Source:
Seltzer, A.M., Ng, J., Aeschbach, W. et al. Widespread six degrees Celsius cooling on land during the Last Glacial Maximum. Nature 593, 228–232 (2021). https://doi.org/10.1038/s41586-021-03467-6
Kala Hunter is a Health/Science/Environment graduate student at Medill. You can follow her on @kalahunter and www.kalahunter.com
