July 29 (UPI) -- Earth's climate is changing at an unprecedented rate, but the planet's climate has shifted abruptly in the past - and throughout history, humans have struggled to adapt to these sudden climatic shifts.
To prepare for future climate change, researchers set out to investigate the "tipping points" that led to historic periods of society-altering climate change.
More specifically, scientists looked at how small changes in the planet's major systems -- its water, air and ice cycles -- can led to major social and economic disruption.
Researchers published their findings Thursday in the journal Nature Geoscience.
"We've been putting a lot of chemicals into the atmosphere and changing the heat of the atmosphere for a long time, and really intensively, for 150 years," study co-author C. Michael Barton said in a press release.
"And, things are still chugging along. Temperatures are slowly going up globally, but we haven't seen a huge, dramatic shift. However, complex systems are potentially vulnerable if you push too much," said Barton, a geoarchaeologist and anthropologist at Arizona State University.
To examine the lead-up to climatic tipping points, researchers relied on data from past surveys of sediment cores drilled from the Gulf of Alaska, dust records pulled from the deserts of North Africa and ice cores extracted from Greenland.
Scientists also surveyed previously compiled records of ocean dynamics -- changes in the levels of salt and oxygen, shifts in major current patterns and influxes of meltwater from shrinking ice sheets.
After pinpointing periods of sudden climate change that impacted human populations, such as the abrupt cooling that triggered crop failures and famine some 1,500 years ago in Europe, scientists examined the shifts in planetary cycles that preceded them.
In Europe, the catastrophic cooling was precipitated by a series of volcanic eruptions, a reminder of how quickly the planet's systems can be severely disrupted.
Researchers also found that tipping points often involved a combination of climate shifts and unsustainable human behavior.
For example, farmers surrounding the ancient city of Angkor steadily depleted the local water table by diverting natural flows to irrigate crops.
As a shift in precipitation patterns solidified across Southeast Asia, the city and its populations were unable to withstand resulting floods and droughts.
While the latest analysis can provide context for the current climate crisis, researchers suggest it is still quite difficult to pinpoint when climate variability becomes the "new normal."
In followup studies, researchers hope to fill in data gaps and develop models that can actually predict abrupt shifts and help governments and economies prepare accordingly.
"As humans, we try to anticipate the future," researchers wrote. "We are now well aware that complex systems, including the coupled social and ecological systems that now dominate our planet, can undergo abrupt changes."
"If we cannot model abrupt change in the past, we cannot hope to predict them in the future," the researchers wrote.