Weird Weather: Is Climate Change to Blame?

Killer tornadoes, epic floods, and now hurricanes! Is it the end times or just predicted changes in climate due to global warming? The short answer is that no one knows for sure, but computer climate models based on data of increases in global temperature show that the an increase in participation levels and storm intensity is expected. No unbiased observer may deny that the last thirty years has exhibited an increasing average global temperature pattern. The first decade of this century was the hottest decade on record since reliable record keeping began in the late 1800's. At the same time global levels of atmospheric CO₂ are steadily increasing [chart]. The latest numbers available for carbon emissions are grim. Despite the global economic crisis of 2008, carbon emissions reached a record high in 2010.  The prospects for limiting global warming to less than the 2℃ agreed to at the Cancun climate talks appear unobtainable now.

Because climate is a long term phenomenon and weather is a daily variable the link between warming and more violent and frequent storms is not readily apparent. There can be intermittent cooling cycles within the long term warming trend. But global warming increases ocean evaporation and the amount of water the atmosphere can hold; that is why global warming is often referred to as the "greenhouse effect". Increased amounts of atmospheric water vapor create conditions for heavier and more frequent precipitation over some areas of the Earth while other areas experience severe droughts. In the United States the amount of precipitation in the heaviest 1% of storms is three times what is was between 1957 and 2007. The northeastern US has experienced a 67% increase in the amount of rain or snow during the heaviest 1% of storms. Of course when the amount of precipitation increases, floods are more extensive and take more lives. The link between tornadoes and climate change is not as established since they are very intense but short lived phenomena whose formation mechanism is not completely understood. Tornadoes are associated with severe thunderstorms which form when hot, moist air near the Earth's surface rises to react with cold, dry air aloft. A rotational wind source such as a strong westerly jet stream colliding with rising warm, humid air gives rise to tornadoes such as the ones that ripped through the southeast in April and May. If greenhouse emissions continue unabated scientists think that precipitation in the heaviest storms will increase by 40%. The presence of more water vapor and associated energy is therefore available to intensify storm activity.  Clearly, more severe storms are becoming the new normal.