Agriculture and livelihoods are already being affected

Failing agriculture in the future have long been predicted.
Food and Global Warming, ScienCentral, January 7, 2009
Looking to 2100, scientists who looked at projections of global warming’s impact on the average temperatures during the growing season fear that rising temperatures will have a significant impact upon crop yields, most noticeably in the tropics and sub tropics.
While warm weather can often be good for some crops, hotter than average temperatures for the entire season is often not good for plants.
This would affect at least half the world’s population that either live in the region or rely on food coming from that region.