© UCAR. Photo by Carlyle Calvin. Used by permission.

Three great weather extremes affected the United States in 2012: a summer drought centered in the high plains, a heat wave that affected most of the country, and Hurricane Sandy. A new report in the Journal of the American Meteorological Society attempts to determine what role climate change had in these events. By climate change, I mean change that has already occurred, not change that is predicted for the future.

The first U.S. weather extreme studied was the summer drought of 2012. (Rupp, Mote, Massey, Otto, and Allen, 2013) This drought was centered in the high plains. It was at its most severe in June, July, and August, but affected the entire agricultural growing season. The study found that average levels of precipitation are expected to decrease as a result of climate change, but not the frequency or severity of extreme dry periods. Thus, over time climate change may be drying out the areas they studied, but most likely it did not significantly raise the likelihood of the extreme drought of 2012.

The second U.S. weather extreme studied was the heat wave of 2012. A spring heatwave led to record high temperatures in the east, followed by a heatwave centered in the plains and midwest during the summer. One group of investigators (Diffenbaugh and Scherer, 2013) found that climate change has made a heat wave like the summer one four times as likely as it would have been previously. A second group of investigators found that the human contribution to the spring heatwave was about 35%. (Knutson, Zeng, and Wittenberg, 2013)

Source: NASA Earth Observatory.

The third U.S. weather extreme studied was Hurricane Sandy. Most of the damage from Sandy was caused by storm surge, and a team of investigators looked at whether climate change had a role in the size of the storm surge. (Sweet, Zervas, Gill, and Park) They measured Sandy’s storm surge at two important locations: Sandy Hook, and The Battery. They found that climate change made a Sandy-level storm surge 50% more likely at Sandy Hook and 48% more likely at The Battery. They also went on to predict the likelihood of similar storm surges if climate change continues. They predicted that under high climate change scenarios, similar storm surges could become approximately annual events by 2100. I don’t usually focus on future predictions, but I thought that deserved mentioning.

The focus on heat and drought serves as a good segue. The next couple of posts will focus on the 2012 drought in Missouri, and whether drought has become more common or more severe.

Sources:

Rupp, David, Mote, Philip, Massey, Neil, Otto, Friederike, and Allen, Myles. Human Influence on the Probability of Low Precipitation in the Central United States in 2012. [in “Explaining Extreme Events of 2012 from a Climate Perspective”]. Bulletin of the American Meteorological Society, 94 (9), S2-S6.

Diffenbaugh, Noah, and Scherer, Martin. (2013). Likelihood of July 2012 U.S. Temperatures in Preindustrial and Current Forcing Regimes. [in “Explaining Extreme Events of 2012 from a Climate Perspective”]. Bulletin of the American Meteorological Society, 94 (9), S6-S9.

Knutson, Thomas, Zeng, Fanrong, and Wittenberg, Andrew. (2013). The Extreme March-Mary 2012 Warm Anomaly Over the Eastern United States: Global Context and Multimodel Trend Analysis. [in “Explaining Extreme Events of 2012 from a Climate Perspective”]. Bulletin of the American Meteorological Society, 94 (9), S13-S17.

Sweet, William, Zervas, Chris, Gill, Stephen, and Park, Joseph. Hurricane Sandy Inundation Probabilities Today and Tomorrow. [in “Explaining Extreme Events of 2012 from a Climate Perspective”]. Bulletin of the American Meteorological Society, 94 (9), S17-S20.