But, it followed a period of global cooling from 1950s - 1970s, and before that an earlier period of global warming from 1920s - 1940s. (globalwarmingsolved.com)
It is natural to have ice ages and periods of global warming as part of the earth's history. (scientificamerican.com)
However, our findings also show that, whatever humans do, the world naturally goes through periods of global warming and periods of global cooling. (globalwarmingsolved.com)