Fig. 1. Observed change in surface air temperature between 1930 and 1990. Temperature change is based on the linear trend as in Hansen et al. (2001). Observations are from the NASA GISS Surface Temperature Analysis (Credit: E.M. Leibensperger et al 2012 Creative Commons)
Reducing air pollution from coal fired power stations has led to a decrease in air pollution. But the Harward School of Engineering and Applied Sciences (SEAS) has now found that particulate pollution, particularly from coal fired power stations delayed global warming. It causes large cold patches, reducing temperatures by up to 1 degree C.