A new study found that more than 200 urban areas are experiencing a significant increase in heat waves between 1973 and 2012.
International researchers at the Indian Institute of Technology (IIT) Gandhinagar, Northeastern University, University of California, Los Angeles, and the University of Washington collaborated in a study that aims to determine the effect of extreme weather worldwide, as well as the differences between urban and non-urban areas. They analyzed the global historical weather and climate data provided by the National Climatic Data Center (NCDC).
The study focused on urban areas that have a population of at least 250,000. Out of the original 650 areas identified, the researchers narrowed their analysis to 217 areas with complete weather and climate data over the last four decades. The team computed the daily temperature, rainfall, and wind speed to measure heat waves and cold waves. A heat wave is a prolonged period of excessively hot weather, while a cold wave is a weather occurrence characterized by cooling of the air.
Initial analysis showed that 63 percent of the urban areas are experiencing extremely hot nights, and this episode lasts for an average of 8 days. There are also less windy days now, at 60 percent, compared to 30 years ago.
The researchers believe that studying the impact of extreme weather on urban areas is critical because any damage will have a negative effect on the economy.
"Over half of the world's population now live in urban areas; hence, it is particularly important to understand how the climate and climate extremes, in particular, are changing in these areas," said study leader Professor Vimal Mishra from IIT Gandhinagar in a news release.
"Urban areas make up a relatively small part of the global land area; however, they are the center of wealth, so damage to urban infrastructure could result in potentially large economic losses. Surprisingly, there have been few studies that have focused on changes in climatic extremes in these areas."
The study was published in the Jan. 30 issue of the Environmental Research Letters.
