They found thousands of places with air concentrations significantly above the 2 parts per million background level typically found in cities, with some areas as high as 100 ppm. (sciencemag.org)
Two billboards compared to hundreds of thousands of places of whorship. (religion.blogs.cnn.com)
They used predictions of two key weather variables - aridity and temperature - and compared them with conditions recorded at thousands of places across Europe and north Africa from 1961 - 1990. (theguardian.com)