Global warming is occurring at an accelerated pace in many high-altitude regions around the world and among the consequences could be water shortages, according to a new study co-authored by Rutgers climate scientist Jim Miller.
A professor in the Department of Marine and Coastal Sciences in the School of Environmental and Biological Sciences, Miller collaborated with an international team of scientists on a new study published in the journal Nature Climate Change. The researchers say evidence is showing that global warming often occurs more rapidly in high mountains and that further study is needed to fully grasp the true impact of the phenomenon.
“Somewhere on the order of 1 billion people a day don’t have access to good clean water,” Miller said. “Climate change will exacerbate that and what happens in mountains is going to be a major part of that.”
Globally, the team of researchers found that as altitude rises, the rate of temperature change often accelerates. In the past 20 years, temperatures above 4,000 meters (13,120 feet) have warmed 75 percent faster than at altitudes below 2,000 meters (6,560 feet).
Miller explained that the snow line on a mountain, rather than specific altitude, is what matters in the rate of warming.
“Snow reflects a lot of solar radiation so, if that snow melts, radiation gets absorbed by the ground which heats the ground and warms the air,” he said. “Right at the snow line, as the snow melts, it gets significantly warmer. And that’s the same sort of thing that happens in the Arctic when the sea ice melts.”
In the United States, areas such as southern California and Arizona, which rely on water brought from the mountains, stand to be most adversely impacted, Miller said.
As snow accumulates later in the fall and melts faster in the spring, less fresh water will emerge from the mountains during the late spring and through the summer. For both agriculture and the water supplies of major cities, that could spell trouble.
“Water is going to be a major problem over the next few decades anyway and climate change is going to exacerbate it,” Miller said. “Who gets the water? Are you going to use the water to grow crops or are you going to use the water to fill swimming pools in LA? Those are ultimately social and political decisions. With climate change, those changes could be more dramatic.”
Beyond water supply issues, the “elevation-dependent warming” phenomenon has implications for tourism, in terms of shorter ski and whitewater rafting seasons, as well as forestry. In Colorado, for example, a spruce beetle infestation has been devastating forests.
“Some people would argue that because the climate is warming, it makes it more favorable for spruce beetles to exist,” Miller said. ”Also, drought conditions make trees less resilient to the beetle.”
The report by the international scientific team calls for improved observations, satellite-based remote sensing and climate model simulations to better understand elevation-dependent warming. In addition, existing observational data from around the world needs to be collated and evaluated. The lead author is Nick Pepin, of the University of Portsmouth (UK).