Go outside and take a long, deep breath. Do your lungs feel suitably refreshed? If you’re in any one of a growing number of cities, the answer to that question may well be ‘no’. According to the World Health Organization (WHO), a staggering 98% of large cities (those with more than 100,000 inhabitants) in low- and middle-income countries do not meet minimum air quality guidelines. The situation is better in high-income countries, but still, less than half of cities are up to standard.


Effective greenhouse gas (GHG) mitigation measures to stabilise global temperature change to no more than 2°C above pre-industrial temperatures would also substantially reduce air pollutant emissions, recent research predicts. A variety of mitigation options are available, including switching from fossil fuels to renewable sources of energy. To achieve the necessary GHG emission reductions, one key option is to impose carbon taxes. However, these would need to be high to help achieve this target, according to the study's authors.

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In addition to causing smoggy skies and chronic coughs, soot – or black carbon  – turns out to be the number two contributor to global warming. It’s second only to carbon dioxide, according to a four-year assessment by an international panel.

“We were surprised at its potential contribution to climate,” said Sarah Doherty, a University of Washington atmospheric scientist and one of four coordinating lead authors.