It's not necessarily less precipitation overall that will cause the megadroughts but higher temperatures that will cause the soil to dry our more than during past droughts.
Not necessarily true. Droughts also occur because precipitation cycles move location due to geological or other natural causes, not necessarily because of a change in air/ground temperature or drop in average frequency or quantity, the rainfall location(s) just move(s).
The present-day Kalahari Desert in Africa used to be a mega-lake named Lake Makgadikgadi.
http://en.wikipedia.org/wiki/L...
Other prehistoric lakes here.
http://en.wikipedia.org/wiki/L...
Significant changes in climate patterns have happened over relatively short periods of time in the past, and massive changes have occurred with some regularity over longer time periods. None of these occurrences were influenced in any significant & meaningful way by mankind. The scale and amounts of energy expended over the time periods that any of those changes took are far beyond the capability of humans for the foreseeable future
To even theoretically cause a measurable and statistically-meaningful change would require a Borg-like singularity and concentration of effort & purpose of the entire human race at current and foreseeable near-future technology levels/abilities our species is capable of.
The amount of inertia in a planetary size system (and that's if we exclude Solar variability induced changes and gravitational forces from other bodies, etc) in motion over such long geologic periods with such massive forces already steering it are many orders of magnitude too large for mankind to be able to cause any truly meaningful long term changes in any direction over a time-frame of only 200-300 years.
And as long as I'm already posting in a thread about AGW and will naturally be down-modded by group SlashThink for having the 'wrong' views, for those who love to trumpet "settled science! consensus! denier!", remember that "Big Bang Theory" and how those who thought the universe was eternal were crackpot nutjobs because it was "settled science"? Seems that bit of "settled science!" may be in serious doubt.
http://phys.org/news/2015-02-b...
Beware anyone who tries to shut down discussion or silence opposing viewpoints, whether it be by arresting journalists and smashing printing presses or through propaganda campaigns of malicious ridicule and personal destruction.
Strat