Could reaching environmental tipping points really impact the Earth’s climate all that much? New research from an international team of four scientists says yes. Their study is the first to show that in our planet’s past, gradual changes in carbon dioxide (CO2) concentrations led to tipping points that then set off temperature spikes of as much as 10 degrees Celsius in only a few decades.
Scientists led by Xu Zhang of the Alfred Wegener Institute were able to show how sudden changes in our climate, or Dansgaard-Oeschger events, came from CO2 concentrations that rose gradually. Researchers had known temperatures shot up thanks to Greenland ice core samples, but they weren’t sure why – and the new study provides some answers. Zhang said in a statement, “With this study, we’ve managed to show for the first time how gradual increases of CO2 triggered rapid warming.”
The team drew on a climate model to find how interactions between the atmosphere and ocean currents led to the temperature spike of 10 degrees Celsius, or 18 degrees Fahrenheit, in Greenland during the last Ice Age, which ended around 11,700 years ago.
Here’s how it works. Increased CO2 strengthened Central America trade winds, and the eastern Pacific Ocean warmed more than the western Atlantic Ocean. From there more moisture left the Atlantic, so the salinity and density of that ocean’s surface waters increased. These changes resulted in an abrupt amplification of the circulation pattern of the Atlantic, which according to Zhang can lead to sudden temperature increases.
Will we see rapid changes if we hit tipping points today? Gerrit Lohmann of the institute and the University of Bremen said, “We can’t say for certain whether rising CO2 levels will produce similar effects in the future, because the framework conditions today differ from those in a glacial period. That being said, we’ve now confirmed that there have definitely been abrupt climate changes in the Earth’s past that were the result of continually rising CO2 concentrations.”
The journal Nature Geoscience published the research online this month.
Images via Coen Hofstede