Climate change poses significant threats to the populous nation
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Summer in Kerala, India. Credit: Vinoth Chandar/Flickr, CC BY 2.0
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A warming of 2 degrees Celsius would cause 34 percent of the world’s population to migrate more than 300 miles, to places on the fringes of the tropics where the temperatures are milder. Dramatic population declines might occur in Mexico, Central America, Africa and India. The results were published today in Scientific Reports.
The scientists are cautious about the predictive power of their thought experiment, particularly as it relates to humans. People, unlike animals, can adapt to higher temperatures through technologies such as air conditioning. They also face barriers to long-distance migration, such as land borders, language barriers or even buying an air ticket. The scientists stressed that they are only exploring a hypothetical response to rising temperatures.
“We’re not making specific predictions about migration patterns of individual species, but the geophysical constraint is that, as the tropics get hotter, you’ll have to go far, essentially leaving the tropics, to cool off,” Adam Sobel, a professor of applied physics and math at Columbia University and a co-author of the study, said in a statement.
Some of the regions that the study suggests would be worst affected currently have the lowest migration rates in the world, said Valerie Mueller, a senior research fellow who studies migration at the International Food Policy Research Institute.
“They try to cast this paper as a way of thinking about not just human, but the migration of other species,” she said. “For birds that have very little costs in moving 500 and 1,000 kilometers [300 to 620 miles], it might work. But this framework for monitoring human migration doesn’t recognize the formidable barriers we face in moving.”
To Mueller, the utility of this study lies in the attention it brings to the topic. The humanitarian community would like to get a better sense of population size in the future, she said.
“The international community basically wants to understand that, given the fact that the world is global and people are moving countries, how can they plan in terms of infrastructure and development, how can they plan the allocation of resources to accommodate this potentially growing population,” she said.
In the study, the scientists have used a simple climate model to say how far humans would have to migrate if they want to continue to experience the same temperatures. Since temperatures are similar near the equator, the climate model shows that people in the tropics would have to move large distances to offset a smaller increase in average temperature, said Andrew Solow, a senior scientist at Woods Hole Oceanographic Institution.
He also stressed that most people do not migrate to continue experiencing their current temperatures.
“My impression is that, in the U.S., populations have tended to shift toward warmer parts of the country over the past decades,” he said.
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