“Studies show that global warming will increase the frequency or intensity of many kinds of extreme weather.” Environmental Defense Fund.
All over the world extreme weather such as droughts, heat waves, stronger hurricanes , heavy downpours, more frequent and more powerful tornados, etc. are being observed.
IPCC Panel: Get Ready for Extreme Weather (11/2011)
Extreme Weather and Climate Change, Understanding the Link, Managing the Risk, June 2011, by Daniel G. Huber and Jay Gulledge, Ph.D. Risk management is the correct framework for examining the link between global climate change and extreme weather. The lack of scientific certainty (connecting an individual weather event and climate change) does not equate to a lack of risk.
Scientific American Series on Extreme Weather, Climate Change, and the Risks We Face (June 2011) http://www.pewclimate.org/science-impacts/extreme-weather
Union of Concerned Scientists. Is Global Warming Linked to Severe Weather?