http://www.reuters.com/article/envir...14481720070711

LONDON (Reuters) - The sun's changing energy levels are not to blame for recent global warming and, if anything, solar variations over the past 20 years should have had a cooling effect, scientists said on Wednesday.

Their findings add to a growing body of evidence that human activity, not natural causes, lies behind rising average world temperatures, which are expected to reach their second highest level this year since records began in the 1860s.