Megacities contribute to global climate change in big way

Washington, Aug 31 ( Megacities, with populations exceeding 10 million, that consume energy, food, water, and other raw materials and release wastes are contributing to global climate change, researchers say.

More than half the world’s population today lives in cities, and the world’s largest urban areas are growing rapidly. The number of megacities has grown from just three in 1975 to about 20 today.

Charles Kolb, from the Centre for Atmospheric and Environmental Chemistry, (CAEC) said: “Carbon dioxide and other pollutants in megacities make them immense drivers of climate change.”

“They impact climate on both a regional and global level because these long-lived greenhouse gases are dispersed around the world.”

Kolb said that the most highly polluted megacities are in developing countries. They include Dhaka (Bangladesh), Cairo (Egypt) and Karachi (Pakistan).

Large cities like living entities, release wastes, which include carbon dioxide, the main greenhouse gas, air pollutants, sewage and other water pollutants and even excess heat that collects in vast expanses of concrete pavement and buildings.

Humans directly produce a significant share of this waste, but emissions from industrial, power generation and transportation systems respire the largest quantities of greenhouse gases and other air pollutants.

Other urban metabolisers include sewage systems, landfills, domestic pets and pests like rats, which in some cities outnumber people, Kolb said.

These findings were presented at the 238th National Meeting of the American Chemical Society, said a release.