The words climate change trigger thoughts of hot temperatures, mass extinctions and melting ice caps. Even though these are all frightening changes, one specific danger that is overlooked by the media is the increase in the incidence rate of violent thunderstorms. Thunderstorms are one of the primary causes of catastrophic loss in the United States. This increase has been hypothesized by several studies based on historical and computational data, conducted by researchers from around the globe (Elsner, 2014). These predictions have been found by several researchers from different parts of the globe. However, these studies come with several uncertainties, due to the following factors. First, there is no reliable long term record of severe thunderstorms with which experts could analyze trends that have risen. Second, theories and climate model prediction have produced contradicting results on the conditions that are required to produce severe thunderstorms. Third, several processes that are important for the production of storms has mostly remained inaccessible in climate models due to the deficiencies in model development.
However, recent advancements in the field have lead scientists to identify two main conditions needed for the production of extreme thunderstorms, that coupled together, have not generated any contradictions within the scientific community. The first is a significant increase in the amount of potential convection available potential energy (CAPE) present in the atmosphere (Diffenbaugh, 2013). CAPE is the amount of energy a parcel of air would have if lifted a certain distance vertically through the atmosphere. In other words, CAPE is the measure of the amount of energy available for convection. (Carbin, 2013). This phenomenon is created as the air of the low atmosphere warms, rising up the air from below, carrying with it moisture to higher altitudes. As result, an increase in temperature would lead to a higher CAPE value. However for an increase in CAPE to produce a thunderstorm, its activity must interact with strong vertical wind shear, the second condition that was identified (Diffenbaugh, 2013). Wind shear is the difference between wind speed and direction over a relatively short distance in the atmosphere. Wind shear can be classified as either horizontal or vertical, terms which describe the direction of the wind shear. In the case of a vertical wind shear, the wind shear is moving from the surface to the troposphere (Carbin , 2013). The combination of these two factors will essentially move wind currents that organize the atmospheric energy and moisture, thereby sustaining a storm.
However, researchers had previously hypothesized that global warming will increase CAPE and cause an overall decrease in wind shear, which created uncertainty about the net effect. In a new climate model experiment called the Coupled Model Inter-comparison Project, confirmed these changes, but in a way that has not been previously theorized. The climate model experiment predicts that there will be an overall decrease in the average amount of wind shear, but the bulk of that decrease occurs on days that produce levels of CAPE that are much lower than levels normally seen during severe storms. However, this model also predicts that more days, in comparison to today’s weather, will exhibit a high enough CAPE coupled with a sufficiently strong wind shear. As a result, since the decrease in the strength of wind shear and the increase in CAPE occurs on separate days, these changes will lead to a net increase in the incidence rate of severe thunderstorms (Diffenbaugh, 2013).
These results predict another phenomenon produced by climate change that can lead to dire consequences. As a result, studies such as the one outlined in this paper, must be publicized in an unbiased manner to the general public, in order to promote changes towards a greener future.
Work Cited
Carbin G, Guyer J, Bentley E, Robinson FT. 2013. The 2013 Tornado Season: Local Devastation. WEATHERWISE:43–51.
Diffenbaugh NS, Scherer M, Trapp RJ. 2013. Robust increases in severe thunderstorm environments in response to greenhouse forcing. Proc. Natl. Acad. Sci. U. S. A. 110:16361–6. http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=3799355&tool=pmcentrez&rendertype=abstract
Elsner JB, Elsner SC, Jagger TH. 2014 Aug 6. The increasing efficiency of tornado days in the United States. Clim. Dyn. http://link.springer.com/10.1007/s00382-014-2277-3