Even a slight slowdown to one of Earth’s major ocean currents could almost halve the rainfall of some of the planet’s rainforests and fuel droughts that could accelerate climate change, new research warns.
The Atlantic Meridian Surrounding Circulation (AMOC), including the Gulf Stream, plays an important stabilization role in the surrounding Earth climate. However, many studies have shown that currents are slowing down, and some suggest that they are heading towards a disastrous collapse.
Now, the new study analyzes climate records from 17,000 years ago, linking current weakening with impacts on the Earth’s tropics. The study, published on Wednesday (July 30) in the journal Nature, suggests that potential impacts present a “stellar risk” that can send normal, humid areas to drought, in Amazon Rainforest and elsewhere.
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“This is bad news because these very important ecosystems are in the Amazon,” said research author Pedro Dinezio, chief author of Atmospheric and Marine Scientists at the University of Colorado Boulder, in a statement. “Amazon Rainforest includes nearly two years of global carbon emissions, making it the major carbon absorption on the planet. Drought in this region can regain enormous amounts of carbon back into the atmosphere and form a vicious loop that exacerbates climate change.”
The AMOC functions as a planetary conveyor belt, moving cold water southwards from nutrients, oxygen and tropical waters northwards.
However, studies on the history of the Earth’s climate show that currents have been turned off in the past, and some studies suggest that the glacial meltwater released by climate change slows down AMOC. The worst-case scenario predicted by some models suggests that current currents can collapse completely during the current century, potentially causing devastating and irreversible effects all over the world.
Related: Atlantic flows are weakening – and that could make the climate in some regions unrecognizable
These predictions are controversial, but the risks are large enough for scientists to seek emergency investigations. The effects of AMOC decline include European plunge temperatures and storms that grow around the equator, but scientists also point out other, less foreseeable effects in the tropical regions of the Earth.
To investigate these possible results, the researchers behind the new study pooled data on cave formation and ancient rainfall patterns preserved in lake and sea deposits. They then inserted them into climate models to simulate past and future changes.
These models predict that weakening of AMOCs will cool the North Atlantic and reduce temperatures in the tropical Atlantic and Caribbean. This change involves rising global temperatures due to climate change, leading to reduced precipitation in areas of the Rainforest Belt, resulting in up to 40% reductions in rainfall in parts of Amazon Rainforest.
However, despite this surprising prediction, researchers emphasize that the situation is not hopeless. Tropics may remain sensitive to small changes in AMOC strength, but they say it is unlikely to completely collapse.
The current fate and how severely slow it will depend on climate change efforts.
“We still have time, but we need to quickly decarbonize our economy and make green technology widely available to everyone around the world,” Dinezio said. “The best way to get out of a hole is to stop digging.”
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