Communicating the links between climate change and heat waves with the Climate Shift Index

Laura Thomas-Walters aYale Program on Climate Change Communication, Yale University, New Haven, Connecticut

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Matthew H. Goldberg aYale Program on Climate Change Communication, Yale University, New Haven, Connecticut

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Sanguk Lee aYale Program on Climate Change Communication, Yale University, New Haven, Connecticut

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Aidan Lyde aYale Program on Climate Change Communication, Yale University, New Haven, Connecticut

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Seth A. Rosenthal aYale Program on Climate Change Communication, Yale University, New Haven, Connecticut

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Anthony Leiserowitz aYale Program on Climate Change Communication, Yale University, New Haven, Connecticut

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Abstract

Extreme weather, including heat waves, poses a significant threat to ecosystems and human health. As global temperatures continue to rise, the frequency and severity of heat waves will increase. Because of this, communicating heat-related risks to the public is increasingly important. One commonly-used communication tool is the Climate Shift Index (CSI), which establishes how much more likely an extreme weather event, such as a heat wave, has been made by climate change. To test the impact of the CSI on people’s understanding of the links between climate change and extreme weather, we conducted an experiment informing 3,902 American adults that climate change made the July 2023 heat wave in the U.S. at least 5 times more likely. In addition to this standard CSI wording and 2 control messages, we also explored the effectiveness of reframing magnitude as a percentage, and whether mechanistic and attribution explanations of the relationship between climate change and heat waves further increase understanding. All treatments increased the belief that climate change made the July 2023 heat wave more likely and is making heat waves in general more likely as well. Additionally, we found that expressing the magnitude as a percentage was more effective than the standard CSI framing. We also found that just talking about the heatwave, without mentioning climate change, was enough to change beliefs.

© 2024 American Meteorological Society. This is an Author Accepted Manuscript distributed under the terms of the default AMS reuse license. For information regarding reuse and general copyright information, consult the AMS Copyright Policy (www.ametsoc.org/PUBSReuseLicenses).

Corresponding author: Laura Thomas-Walters, laura.thomas-walters@yale.edu

Abstract

Extreme weather, including heat waves, poses a significant threat to ecosystems and human health. As global temperatures continue to rise, the frequency and severity of heat waves will increase. Because of this, communicating heat-related risks to the public is increasingly important. One commonly-used communication tool is the Climate Shift Index (CSI), which establishes how much more likely an extreme weather event, such as a heat wave, has been made by climate change. To test the impact of the CSI on people’s understanding of the links between climate change and extreme weather, we conducted an experiment informing 3,902 American adults that climate change made the July 2023 heat wave in the U.S. at least 5 times more likely. In addition to this standard CSI wording and 2 control messages, we also explored the effectiveness of reframing magnitude as a percentage, and whether mechanistic and attribution explanations of the relationship between climate change and heat waves further increase understanding. All treatments increased the belief that climate change made the July 2023 heat wave more likely and is making heat waves in general more likely as well. Additionally, we found that expressing the magnitude as a percentage was more effective than the standard CSI framing. We also found that just talking about the heatwave, without mentioning climate change, was enough to change beliefs.

© 2024 American Meteorological Society. This is an Author Accepted Manuscript distributed under the terms of the default AMS reuse license. For information regarding reuse and general copyright information, consult the AMS Copyright Policy (www.ametsoc.org/PUBSReuseLicenses).

Corresponding author: Laura Thomas-Walters, laura.thomas-walters@yale.edu
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