Posted: 12/30/2008 - 23 periods of climatic warming and cooling have occurred in the past 500 years. Each period of warming or cooling lasted about 25-30 years (average 27 years). Two cycles of global warming and two of global cooling have occurred during the past century, and the global cooling that has occurred since 1998 is exactly in phase with the long term pattern. Global cooling occurred from 1880 to ~1915; global warming occurred from ~1915 to ~1945; global cooling occurred from ~1945-1977;, global warming occurred from 1977 to 1998; and global cooling has occurred since 1998. All of these global climate changes show exceptionally good correlation with solar variation since the Little Ice Age 400 years ago.