The impact of climate change may be sorely underestimated for many island nations, home to nearly 18 million people. Aside from rising sea levels, dwindling resources and subsequent economic downfall, new research shows that islands are in for a exceptionally dy future.
The problem is thousands of island nations are too small to be evaluated in traditional climate models used by scientists to measure the effects of climate change. However, new methods revealed as much as 73 percent of the world's islands will be substantially more arid by mid-century.
What's more is the effect of climate change on the islands' freshwater systems appears to be woefully incomplete. Previously, climate models failed to account for surface evaporation.
"Islands are already dealing with sea level rise," said Kris Karnauskas, lead author and 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."
Global climate models simply are not designed to pick up on what is merely a "freckle" of land on the Earth's massive surface. That's why climate change-driven impacts on freshwater systems of small islands have not been measured - until now.
Available freshwater is largely dependent on precipitation and evaporation. The good news is current climate change models show how much precipitation is likely falling from the sky over a given area. But evaporation is much harder to model, specifically on small islands.
That's where Karnauskas' new models come into play.
With the help of colleagues from the Woods Hole Institute in Massachusetts, Karnauskas developed a new way to estimate precipitation.
The idea is that researchers can now infer an island's actual climate by assessing the climate just above its surface. This is possible because many island nations are so small that climate above the island isn't much different from climate above the ocean, especially averaged over a day or longer.
"We called it the blind pig test," Karnauskas added. "If you were a blind pig flying in this area, would you know there was an island here? Could you feel a difference in the heat or the humidity?"
In other words, a "successful" blind pig test indicates you can't tell if you're over land or over ocean. This means that data doesn't have to be specifically calculated from the land itself to predict evaporation - scientists just need to know what's happening in the atmosphere right above the island surface.
A more accurate ratio of precipitation to evaporation is vital not only for evaluating climate change, but also for assessing the health and safety of people living on these remote islands, as rainwater is a key source of fresh drinking water.
"There's an opportunity to get important information out there," Karnauskas concluded. "This is a framework to provide more accurate information on what to expect."
Their study was recently published in the journal Nature Climate Change.
