WELLINGTON, Aug. 12 (Xinhua) -- Climate change risks ruling out 90 percent of northern hemisphere cities as hosts of the Summer Olympics by the end of the century, a New Zealand researcher said Friday.
Heat stress due to climate change would limit where and when the Summer Olympics could be held in the future, said Professor Alistair Woodward, head of Auckland University's department of epidemiology and biostatistics.
Woodward, coauthor of a study at the impact of increased temperatures on northern hemisphere countries' ability to stage the iconic Summer Olympics marathon, said 90 percent of cities would be too hot and humid for the event by 2085.
"Only three cities in North America, two in Asia and none in Africa will fall in the low risk category," Woodward said in a statement.
"Projections to early next century suggest the last cities with low-risk summer conditions will be Belfast, Dublin, Edinburgh and Glasgow."
Increasing restrictions on when, where, and how the Games could be held owing to extreme heat were a sign of a much bigger problem, Woodward said in a statement.
"If the world's most elite athletes need to be protected from climate change, what about the rest of us?" he said.
"Climate change threatens human health in many ways through heat waves, extreme weather events, and shifts in disease vectors, as well as economic and social stresses on populations living in or trying to escape areas affected by seawater intrusion, drought, lower agricultural productivity, and floods."
In the short term, most of thee impacts could be lessened by actions to reduce background disease risks and other known causes of vulnerability.
"The world beyond 2050 poses increasingly difficult challenges, not only because of the inherent uncertainties in long-term predictions, but because the extent and speed of change might exceed society's ability to adapt."
As more than half the planet's workforce worked outdoors, primarily in construction and agriculture, society faced an increasingly serious trade-off between population health and labor productivity.
"The risk to workers' health could be minimized if workers are allowed to sit in the shade during the hottest times of day and take breaks during hot, humid months," he said.
"Otherwise, exertional heat stroke and its negative outcomes, including mortality, will become a large part of outdoor work around the world."