At the same time, extreme droughts turned forests in Asia, the Mediterranean region, Mexico, Central America, Florida and California into tinderboxes.

CNN: Global warming may harm human health

Extreme droughts currently cover about 2% of the world's land area, and that is going to spread to about 10% by 2050.

BBC: Man with dead camel in desert. Image: Jim Loring/Tearfund

"If extreme droughts like these become more frequent, the days of the Amazon rainforest acting as a natural buffer to man-made carbon emissions may be numbered, " forest ecologist Simon Lewis, from University College London, has said.

CNN: Drought-stressed trees face race to adapt

On top of the effects of the warming trend come more frequent and extreme weather events such as droughts, floods and storms which directly cause death and injury and open the door to other serious health problems, according to WWF.

CNN: Global warming may harm human health

Extreme events like superstorms and super-droughts cross all boundaries, political and geographic.

FORBES: Rebuilding In A Warming World

Now 2012 is officially in the books as the hottest year on record for the continental United States and the second-worst for "extreme" weather such as hurricanes, droughts or floods, the U.S. government announced Tuesday.

CNN: NOAA: 2012 broke U.S. heat records

Droughts and floods are becoming more extreme.

ECONOMIST: Water rights

Extreme weather events, physical disruption to infrastructure or prolonged droughts all threaten unwanted supply disruptions.

FORBES: Business in a Post-Holocene World

More heat in the atmosphere is likely to cause (and arguably is already causing) more extreme weather events, including intense heat, cold, droughts, floods, and storms.

FORBES: Climate and the Rising Threat of Hurricane Floods