"To meet these new standards, especially for ozone and PM2.5, a strategic shift in pollution-reduction measures will be required," says Shao. Unlike sulphuric dioxide and carbon monoxide, which are directly emitted by their sources, ozone and PM2.5 are secondary pollutants that are formed by chemical reactions between a range of different precursors in the atmosphere. “This means we should cast our net much wider rather than focusing on just a few precursors,” says Shao.
Beijing has the most stringent emission controls in China, but a significant fraction of its pollutants come from surrounding regions, says Zhu. During the 2008 Beijing Olympics, for instance, air masses from the south could contribute to 34-88% of peak ozone concentrations in the city. “Beijing’s air quality will not be significantly improved unless the current measures are able to break administrative boundaries,” says Zhu.
Beijing’s approach should be applied in other large cities in the developing world, researchers said at the conference. Otherwise, “megacities will become a main source of global pollution”, says Molina. “How governments meet the challenges of rapid urbanization will determine the quality of life in the future.”
This article is reproduced with permission from the magazine Nature. The article was first published on October 12, 2012.
See what we're tweeting about
6 Comments
Add CommentHelp me out here, isn't urban synonymous with city, (latin urbanus, city)? So how does the following work..." Just over half of the population currently dwells in cities, and with the urban population expected to nearly double by 2050, that proportion is projected to approach 70%. "? What am I missing here? Cities vs megacities? The suburbs? Urban "sprawl"? And finally, megacities are over 10 million but how are the megacity boundaries defined or set?
Reply | Report Abuse | Link to thisThe overall population is not set to double, but population in cities is, hence the proportion living in cities is likely to rise to 70%.
Reply | Report Abuse | Link to thisIt's not surprising, given the breakneck pace of development. One can guess at the effects on healthcare and the environment, as well as social development... I'm guessing it's a rerun of 1960's tower blocks.
Yes, the overall population is set to double. And the mega-city is the quantitative answer. The quality is uncertain, and there will certainly be a wide and changing range of conditions. The two biggest things that will affect quality will be the planning and regulation of growth; and pollution.
Reply | Report Abuse | Link to thisMoving from suburban sprawl to walkable community saves 60% energy use, so it is really a design problem. China's new cities are designed using 1950 planning models copying USA sprawl with superhighways and super traffic. Great design bringing green into high density places; such as Jefferson's checkerboard and linear parks and human powered infrastructure as pervasive as poison powered; and second glass envelopes around skyscrapers within which food is grow on conveyor belts will make the cities far less polluting and far more sustainable. All that is needed is to hire great architects like me to design the new ones and redesign the old; great design is also cost effective because it grows towards using our structures the full 168 hours in a week by combining mixed uses and designing flexible spaces.
Reply | Report Abuse | Link to thistoday's urban population is 50% of 7 billion = 3.5 billion. by 2050 it should double to 7 billion = 70% of 10 billion.
Reply | Report Abuse | Link to thisI believe high rise vertical urban farms could substantially reduce pollution in these megacities by increasing oxygen levels in the cities and reducing the carbon footprint of food. Also, city planners should implement regulations on the type of vehicles that are allowed in these cities, like MPG restrictions, and even phase out of fossil fuel powered vehicles altogether by a near future date. Also, I believe that megacities should start using large scale solar or wind powered atmospheric water generators to provide supplemental water for the city. And, in regards to ground level ozone, it is my understanding that pollution from tailpipe emissions from cars/trucks interact with heat and sunlight to create ground level ozone. So, if cities were to add giant solar panels to the top of their high rise buildings then it will block a lot of the sunlight and heat from hitting the ground and thus reduce ground level ozone while creating energy at the same time.
Reply | Report Abuse | Link to this