Heat, Climate Extremes, and Relativity…

Heat, Climate Extremes, and Relativity…

So, it is summer time in North America and it’s hot. No surprise there right?!? Well, actually it has been really hot. Temperatures reached more than 90 degrees Fahrenheit in parts of Alaska in mid-June, shattering records for many parts of the state. Many of the Western states saw similarly high temperatures, including a high temperature in Death Valley of 129 degrees Fahrenheit on June 30th, not quite record, but still hot.

The thing is that this isn’t just a once in a lifetime heat wave, or that one year that is just abnormally warm and you’ll be talking about for decades to come. It is part of a clearly observable trend to more extreme weather. In 2011 alone, there were 14 extreme weather events that each caused more than $1 billion in damages. These events included: extensive and intense droughts in the Southern Great Plains and Southwest affecting crops and agriculture; tornadoes in the Midwest; and Hurricane Irene in the Northeast. Extreme heat, flooding, droughts, and wildfire risks have not been limited to the United States but have been increasing throughout the world.

What is considered “extreme” in one part of the country isn’t necessarily “extreme” in another part of the country. For example, communities in Texas and Arizona have adapted to living in environments where summertime temperatures frequently exceed 100˚ F and there is extensive use of air conditioning. So, for these communities, temperatures above 100˚ F may not be considered extreme. However, 100˚ F in Seattle or 90˚ F in Alaska are a very different situation. Few, if any, buildings have air conditioning so these temperatures have the potential to significantly affect sensitive segments of the population including the elderly, young, and those with pre-existing health conditions. 

Climate Access members and others are now starting to normalize “extreme events” to the context of the region in order to identify vulnerability thresholds specific to the community and inform planning. This has been done with the forthcoming National Climate Assessment, where they have created maps that highlight the changes to extreme events relative to a historic baseline. They set “extreme” thresholds for high temperatures, heavy precipitation, and warm nights based on the historic 98% exceedance values (thresholds that are only exceeded 2% of the time annually, 6-7 days a year) and then looked at how many times these thresholds would be crossed annually with different climate scenarios.  

The same approach is also being done quite effectively by Cal-Adapt. Here you can find maps such as those below that show the previous historic extreme high temperatures (based on the same locally specific 98% exceedance) and projections of future changes to those extremes.

If you look closely, for both San Francisco and Bakersfield the extreme heat threshold was exceeded four times a year historically and is projected to increase to between 20 and 30 times a year by the middle of the century. But, highlighting the fact that what is extreme in one location isn’t necessarily extreme in another, the extreme heat threshold in San Francisco is 78˚ F, where in Bakersfield it is 105˚ F. It is still early in the use of these customized community specific extreme thresholds, but there is hope that this approach will make the results more meaningful and more relevant to the communities that are using them.  Thus, they could be a good step in communicating climate information to the people who need it and making the climate impacts more relevant and usable for planning and preparedness efforts.

Communities across the U.S. are tackling this issue in different ways and beginning to prepare for more frequent or more intense extreme events. Many cities have extreme heat response plans and open cooling centers during extreme heat events. For example, in New York, common community gathering locations such as community centers or senior centers become the cooling centers. In June of 2012, 445 centers were opened across the city to keep residents cool. In Chicago they also open community centers to help people stay cool and have a tiered warning system with heat watches and warnings triggered when one day is forecast to be over 110˚ F or three consecutive days are forecast to be over 100˚ F. There is an underlying communications question here about how best to spread the word about extreme heat events and motivate vulnerable populations to make use of these services.  With changing climate conditions will “heat watches” and “heat warnings” still be effective?  As an example, in the summer of 2011, Austin, TX had 90 days over 100˚ F.  With such consistently high temperatures, does the public still listen to the “heat warnings” when the local meteorologist mentions it on the nightly news or do they tune it out?

Tucson, Arizona provides another example. They are completing a climate vulnerability assessment and adaptation planning process led by the city and supported by CLIMAS (one of NOAA’s Regionally Integrated Sciences and Assessment Centers located at the University of Arizona in Tucson), and a consortium of private organizations (Cascadia Consulting, Adaptation International, and the Stockholm Institute for the Environment). In this project, the group is combining downscaled climate projects of extreme heat and precipitation with existing social-economic vulnerability to identify critical neighborhoods. The results of this analysis will help Tucson target its adaptation and climate preparedness strategies to the neighborhoods that truly need them and make the most of the city’s budget.

So, yes, it’s Hot!  But, as Einstein first pointed out, it is all relative. Tailoring climate solutions to community specific thresholds allows communities to better understanding the potential impacts of climate change because the impacts are then framed in terms that the community is already familiar with.  It also helps them make the most of their finite resources and prepare for the climate impacts that truly matter to them.


Sascha Petersen is a senior program officer with the Institute for Sustainable Communities and managing director of the American Society of Adaptation Professionals, a professional society for people working on climate change adaptation across the United States.  He is a lead author for the Great Plains Region of the National Climate Assessment, co-founder of Adaptation International and has been a Climate Access member since 2011. 

Photo via (cc) Flickr user bossco