Overall, precipitation over land increases by about 5 %, while precipitation over ocean increases 4 %, but with regional changes of both signs. (ipcc.ch)
Instead they found that the natural influence on precipitation over land areas with observations in the 30 to 60N latitude band is indistinguishable from the natural + anthropogenic signal indicating that anthropogenic forcing has played no detectable role in the evolution of seasonal precipitation in this latitude band either in seasonal or annual totals. (cato.org)
First published in 2007 by two Russian physicists, Victor Gorshkov and Anastassia Makarieva, the still little - known biotic pump theory postulates that forests are the driving force behind precipitation over land masses. (news.mongabay.com)