A new study predicts that 73% of islands will become substantially more arid by mid century, up from an estimate of 50 percent.
From the Caribbean to Easter Island to Hawaii, a majority of islands are facing a risk of drying up due to climate change. New research estimates that the small islands in the Caribbean, Pacific and Atlantic will become substantially more arid by mid century.
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Previous analysis suggested that almost half of all small islands will become drier with the rising temperatures and increased water evaporation, but the latest research predicts that the ratio is much higher than initially estimated. Almost 73% of islands are at risk of drying out, meaning local residents are likely to face increased freshwater scarcity, less agricultural production, vegetation and wildlife and threats to infrastructure that maintains the unique ecosystems of those islands.
"Islands are already dealing with sea level rise," said lead author Krins Karnauskas, a professor of atmospheric and oceanic sciences at the University of Colorado Boulder. "But this shows that any rainwater they have is also vulnerable. The atmosphere is getting thirstier, and would like more of that freshwater back.”
The current global climate models (GCMs), which are used by scientists to measure the effects of climate change, appear to have a flaw. These models divide the planet into a grid and do not consider those thousands of islands that are very small in size.
"Think of pixels," said Karnauskas. "If they're too big to resolve the freckles on someone's nose, you won't be able to see those freckles. You have to have super fine pixels to resolve it and frankly, that’s not what global climate models were designed to do.”
To understand how climate change will affect freshwater sources and aridness, scientists have to understand what's happening with rainfall and evaporation.
When it comes to small islands, the models don't show how much water evaporation is taking place there because those islands don't exist in the models--it's all ocean there. Without knowing how much water is evaporating off the islands, there is no way to estimate exactly how the freshwater supplies are going to be affected by the climate change.
To solve this problem, researchers looked at the climate above the surface of the island to get an idea about the island’s actual climate. Since these islands are small, the climate above them isn't much different from climate above the ocean.
Researchers obtained information about precipitation above the ocean from current GCMs because these models keep record of atmospheric data that would impact the evaporation from the land’s surface such as wind, temperature and solar radiation.
From that information, and some tools borrowed from the engineering field, researchers were able to estimate how much water is evaporating and, thus get a more accurate picture of the affects of rising temperatures on small islands.
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This finding is important, both for understanding climate change in these regions and for human health and safety since a vast majority of the people living on these remote island rely on rainwater as the source of their drinking water and any disruption in those systems can potentially aggravate their problems.