What was done
The author examined monthly maximum and minimum temperature data for urban and suburban areas of Nagpur, India in an effort to explain why various researchers have noted a cessation of warming, or the induction of actual cooling trends in the central urban areas of "most of the Indian industrial cities" since the late 1950s.

What was learned
Although the suburban area of Nagpur has warmed over recent decades "because of global warming" and "because the urban heat island has been intensifying," the central urban area has cooled, especially during the day, because of "increasing concentrations of suspended particulate matter."

What it means
The cooling of the maximum temperature that is noted in the urban centers of India's large industrial cities suggests that the anthropogenic production of particulate matter in these areas is providing an impetus for cooling that is overpowering both the natural warming tendency of the globe and the intensifying urban heat island effect.  Any increase in the atmosphere's current burden of airborne particulate matter could therefore be expected to have a powerful cooling influence on the world's climate.