Our research, which was published in Science Today, shows that abrupt climate changes occurred across the Northern Hemisphere into the Southern Mid-Latitudes simultaneously and within a decade of each other during the last glacial era. We have also pinpointed the exact time of these abrupt climate changes, which is much more precise than previously.
This will help us to predict the impact of sudden climate change in the future.
Climate change can occur in abrupt waves.
Scientists can look back at Earth’s climate through the long ice cylinders called ” Ice Cores” that were drilled out of the Greenland Ice Sheet. The chemical composition of the ice cores reveals that the temperature in the atmosphere has repeatedly warmed up by 8-16degC within a few decades.
A core of ice. Ancient ice cores can tell us about the climate of the past. AAP Image/ACECRC
The warming events were followed by periods of gradual cooling. These abrupt events of warming and cooling occurred more than 25 different times during the last glacial era. They are called Dansgaard Oeschger Events. These events are a reflection of changes in the circulation patterns of the Atlantic Ocean.
We have climate records from many places, but the timing of the changes in Greenland compared to the differences across the northern hemisphere and into the subtropics of the south is not fully understood.
This has not been easy to resolve because we need very precisely dated records to make exact comparisons in timing. Ice cores provide a wealth of information about Dansgaard-Oeschger events. But while they faithfully reproduce the patterns of past climate, they are difficult to date very precisely.
Crystal time capsules beneath our feet
We chose to date climate records from stalagmites in caves.
Stalagmites, or cave mineral deposits that build up on the cave’s floor layer by layer are a result of cave mineral deposits. Water dripping down from the ceiling of the cave feeds their growth. This water also carries a chemical message about the temperature and rainfall above the cave. The crystal structure of the stalagmite traps this signal.
Stalagmites are dated with great precision by measuring the decay rate of uranium that is trapped within them. This feature allows us to compare climate events across different locations.
Stalagmites contain chemical signals that tell us what the climate was like in the cave thousands of years ago. Shutterstock
But long and high-quality records of stalagmite are rare. Scientists around the globe have worked for over 20 years on producing these records. Now that we have enough records, we can compare the timing of Dansgaard and Oeschger events in different regions.
We compared and collated 63 stalagmite records published from caves across Asia, Europe, and South America and determined the timings for abrupt climate change in each.
What we Found
Our results show that climate changes in Asia, South America, and Europe were felt within decades of each other during each Dansgaard Oeschger event. Amazingly, we can determine such a high level of synchrony, considering the events that occurred tens or thousands of years ago.
As Greenland’s temperature increased, sudden changes also occurred in Europe and Asia, as well as in the rain and air temperature systems of South America and Asia.
Read more: Delving deep into caves can teach us about climate past and present.
So why is this important? First of all, finding that climate change events occurred in lots of different parts of the world within decades provides clues as to how they started in the first place.
This tells us that the changes likely spread from the North Atlantic to these locations due to a reorganization of atmospheric circulation patterns. Knowing this will help scientists to narrow down the triggers that are still undetermined.
Our findings also mean that the exact ages of stalagmites from the ice cores can be used for better dating, which enhances one of the most significant records we have about the last glacial climate.
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Future implications
The abrupt climate change we studied took place under conditions that were very different from the current climate.
Humans will not experience Dansgaard Oeschger until many thousands of years when the Earth reaches glacial temperatures again.
However, putting together the puzzles of past abrupt climate change will help us understand what might happen in the future. Our findings, for example, will validate climate models that are used to predict climate change.