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The Silent Killer: Extreme Heat in the Western U.S.

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The National Climate Assessment (NCA) makes an important statement: the trends in heat waves for the western U.S. are alarmingly clear and pose a major threat for the local population. Heat waves are becoming more common and more severe in this region and their increase in frequency and severity is consistent with a warming world.

NASA Aqua satellite image during the western US heat wave of 2006.

NASA Aqua satellite image during the western US heat wave of 2006. Image: NASA

This post is part of a series on the National Climate Assessment. Learn more about climate change where you live by attending a UCS webinar.

This post is part of a series on the National Climate Assessment. Learn more about climate change where you live by attending a UCS webinar.

Heat stress is the major factor when an individual is exposed to extreme temperatures. Since the start of the century, we have seen heat waves act as a “silent killer” in major events occurring in Europe, Russia, and California and Nevada. During the 2006 California/Nevada heat wave, 163 people died. In addition, more than 25,000 cattle and 700,000 fowl were also lost.

Heat waves are especially dangerous in urban regions due to the urban heat island effect, which increases electricity demand for air conditioning. A warmer city with high population density poses a dangerous and complicated test for emergency management, as was seen in Fresno during the 2006 heat wave. Rural regions are also highly affected by extreme heat, especially in a location such as California’s Central Valley. There, the livelihood of countless agricultural workers are affected.

One specific aspect about the trends in heat waves is mentioned briefly in the NCA: heat waves are becoming more moist. Thus, the type of extreme heat events the region has experienced since the turn of the century include very warm nights. This is especially hazardous because it does not allow for a cooling period to recover from the daytime heat. A study led by Alexander Gershunov of the Scripps Institution of Oceanography showed how recent heat waves are much stronger due to warmer nights when compared with events before the year 2000, suggesting a link with global warming.

Increasing average July minimum temperatures for Pasadena, California, based on United States Historical Climatology Network observations. Image by author

Increasing average July minimum temperatures for Pasadena, California, based on United States Historical Climatology Network observations. Image by author

Extreme heat will remain as one of the top health threats associated with climate change, the NCA points out. The detected trend in nighttime temperatures is clear throughout the region, as evidenced by observations in locations like Pasadena (see plot above). It is important for policy makers to take these facts under consideration.

Posted in: Global Warming Tags: , , , ,

About the author: Roberto Mera is a climate scientist and Kendall Science Fellow in climate attribution. His work entails analyzing specific carbon emissions to determine how they are affecting global temperatures and extreme heat events. He holds a Ph.D. in marine, earth and atmospheric science from North Carolina State. See Roberto’s full bio.

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  • http://www.ucsusa.org/about/staff/staff/robreto-mera.html Roberto Mera

    Thanks, Aaron. Air conditioners are certainly important in this conversation for two reasons: (a) they can help ameliorate the situation for exposed populations in cooling centers and (b) they stress the electricity demand (http://www.sciencedaily.com/releases/2008/07/080710125527.htm). Some cities have cooling centers for people at risk (elderly, young children) during heat waves. Today, in many locations people don’t consider air conditioners necessary due to the past climate. However, the climate is changing and this will need to be addressed. For example, in Europe, coastal California, higher altitudes of the Appalachians the majority of indoor living spaces don’t have air conditioners. The lack of the ability to cool people off is what killed so many in heat waves in Europe (2003), Russia (2010) and California (2006). So, back to your point, air conditioners are a commodity and sometimes make us unaware of the true nature of a heat wave, but not everyone is so lucky and the consequences can be severe. However, this technology can save lives if used correctly in a heat extreme setting.

  • Aaron

    I think air conditioning is one of the main reasons business and government leaders don’t address climate change. As long as they can sit on their butts in perfect comfort and sleep in nice, cool beds during brutal heat waves, they don’t care how others suffer. It’s always amusing when I hear somebody get outta their big car at the store on a really hot day and say how ‘beautiful’ it is. Yeah, that’s because you’ve only been out of the AC for 20 seconds as you waddle into the store’s climate controlled conditions to pile on a few thousand more calories, which are heat also. Two summers ago, I lived through the hottest summer without AC, and it’s about the worst thing there is, when it’s day and night, it makes the simplest daily activities terribly difficult and folks get irritable and crime spikes also.

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