Add Lack of Freshwater to Island Dwellers’ Woes Under Climate Change
But research published Monday in the journal Nature Climate Change suggests that in addition to altered rainfall patterns and aquifers swamped by seawater, small-island inhabitants may well face an additional stress on their freshwater supplies: significantly drier conditions overall as rising temperatures cause more moisture to evaporate from the land.
Being mostly small, and far from the centers of power, these countries often fall through the cracks of climate science. That’s especially true of models that predict scenarios under varying levels of greenhouse gas emissions.
The United Nations Intergovernmental Panel on Climate Change’s fifth assessment report, released in 2013, is the major guidepost for governments, businesses, aid groups, and other entities trying to plan for the shifting climate. Yet, said Kristopher Karnauskas, a climate scientist at the University of Colorado Boulder, “if you flip open an IPCC report or any number of papers that have come out in the past five to 10 years on changes in drought, aridity, soil moisture—something beyond changes in rainfall—you’ll see beautiful maps, but the ocean is completely blank. If you live on an island that’s smaller than a pixel in the climate model, that island doesn’t exist in the model.”
So Karnauskas, who specializes in the effects of climate change on ocean currents and the water cycle, led a research team that found a way to flip the emphasis in climate modeling to account for these areas, which they term “sub-grid scale islands,” and their 17.6 million inhabitants.
“Given our present trajectory and lack of serious implementation of climate policies with teeth, by mid-century roughly three-quarters of people living on small island nations scattered around the global ocean are predicted to experience increase aridity,” Karnauskas said.
Around 16 million small-island residents could see up to a 20 percent increase in local aridity by 2050, compared with average conditions between 1981and 1999, while 6.1 million face a potential increased aridity of 20 to 40 percent by 2090, the study found.
“This is something we can control,” Karnauskas said. “We have our hand on the dial as far as CO2.”
The small islands likely to experience the sharpest increases in aridity by century’s end, according to the study, include the Juan Fernandez Islands and Easter Island, both territories of Chile; the Lesser Antilles; the Tuamotus of French Polynesia; and the Azores.
In some cases the projections for small-island states aligned with prior forecasts for nearby larger landmasses, the study noted, such as the Greater Antilles, which includes Cuba and Hispaniola (home to Haiti and the Dominican Republic) and has a population of about 40 million people.
Mathew Barlow, a climate scientist at the University of Massachusetts Lowell, and a contributor to the IPCC fifth assessment report, termed the study "an important step in better understanding the impacts of climate change on island nations."
"I strongly agree with the authors' premise that island nations merit special consideration with respect to global warming," Barlow said in an email. "It's a cruel irony that in addition the fundamental inequity of bearing a disproportionate impact despite almost no responsibility for the problem, the local climate of these nations is almost completely unresolved by the models."
Simon Mason, a senior scientist at the International Research Institute for Climate and Society at Columbia University, said Karnauskas’ approach was “interesting,” but the time horizon was too far out to be very reliable. Fifty or 75 years from now “is just too far into the future to have confidence in the results [because] the global models have too many fundamental problems for us to try and pick out small details. I would really like to see this being used at the shorter time scales [because] they’re trying to address a very important question.”
Karnauskas countered that his study accounted for uncertainties and was comparable to any research relying on current climate modeling. “Anyone can raise the point that climate models are imperfect,” he said. “The further out into the future anyone tries to project, the less certain the results become. We’re not the first ones to apply this methodology to water shortages; we’re the first to apply it to small-island nations.”