So is all this crazy weather actually a by-product of global climate change? It turns out the answer isn't quite as simple as "yes" or "no."
Henri Grissino-Mayer is a climatologist at the University of Tennessee. He admits the weather this spring has been extreme, but he's reluctant to place the blame on man-made global warming.
"There's severe weather every year. So it's hard to make that connection," Grissino-Mayer says.
Grissino-Mayer says that climate change due to human causes is happening—"There's no doubt about it," he says, adding that the atmosphere today has a completely different chemical composition than it did 150 years ago—but extreme weather can't be solely attributed to the Greenhouse Gas Effect.
He says this spring's and summer's terrible storms could be caused by global warming: Warmer air means the lower atmosphere can absorb more water, which means more potential for storms. (According to the World Meteorological Organization, 2010 culminated the hottest and wettest decade on record since their record-keeping started in 1850.) But Grissino-Mayer also notes that volcanism (aka, volcanic eruptions) is another possible cause of climate change, and 2010 saw that massive explosion in Iceland.
"Yes, there has been more unstable weather and there have been severe storms, but the reality is there is so much we don't know," Grissino-Mayer says. "It is entirely possible that it is human-caused. But there is no proof, and as a scientist, I need proof."
But the lack of definitive evidence isn't stopping other scientists from proclaiming a cause and effect. Jeff Masters, the director of meteorology and co-founder of the popular weather website Weather Underground, recently wrote on his blog, "Looking back … I can't find any years that had more exceptional global extremes in weather than 2010, until I reach 1816. That was the year of the devastating ‘Year Without a Summer'—caused by the massive climate-altering 1815 eruption of Indonesia's Mt. Tambora, the largest volcanic eruption since at least 536 A.D. It is quite possible that 2010 was the most extreme weather year globally since 1816. …
"The pace of extreme weather events has remained remarkably high during 2011, giving rise to the question—is the ‘Global Weirding' of 2010 and 2011 the new normal? … [I]t is highly improbable that the remarkable extreme weather events of 2010 and 2011 could have all happened in such a short period of time without some powerful climate-altering force at work."