A brief note about global warming
For those that take every sign of decreased rainfall as a sign of global warming, don't. Global warming might cause localized drought because of changes in weather patterns, but a higher average temperature tends to put more moisture in the air, just like raising the temperature on a covered pot on the stove. A disruption in the Atlantic Conveyor would cool temperatures in northern Europe which could definitely lead to drought there, but that will probably mean more extreme weather and flooding somewhere else -- you might see rain in the Sahara and force-5 hurricanes hitting the Atlantic seaboard.
That's the weird thing. Global warming is probably a bad thing for most of the places people like to live at present -- people like pleasant weather, and any disruption in the climate is generally going to be worse for them. For those now living in harsh conditions -- Siberia, Alaska, Northern Canada, the Sahara, Southwestern U.S., etc -- some places might actually have improved climate.