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Climate Change Science

Understanding the Link Between Climate Change and Extreme Weather

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Changes in Extreme Weather and Climate Events

Scientists study many aspects of change in extreme weather and climate events. These include:

  • Frequency: Are events occurring more often than they did in the past?
  • Intensity: Are events getting more severe, with the potential for more damaging effects?
  • Duration: Are events lasting longer than "the norm"?
  • Timing: Are events occurring earlier or later in the season or the year than they used to?

Extreme weather is typically rare. But climate change is increasing the odds of more extreme weather events taking place.

Climate Change and Extreme Weather

An image of a bell curve showing how incidence of extreme weather changes as average temperature increases. Extreme hot weather becomes more common while extreme cold weather becomes less common. Watch the Extreme Weather Bell Curve Animation(1 pg, 342 K)  to learn how this shift is happening. (requires Flash) 

Establishing the most likely causes behind an extreme weather event can be challenging, since these events are due to combinations of multiple factors, including natural variability. Nevertheless, scientists have been able to draw a connection between some types of extreme climate patterns—an even some individual events—and climate change. A good way to think about this connection is to focus on whether an extreme weather event was made more likely by climate change.

There have been changes in some types of extreme weather events in the United States over the last several decades, including more intense and frequent heat waves, less frequent and intense cold waves, and regional changes in floods, droughts, and wildfires.[1] This rise in extreme weather events fits a pattern you can expect with a warming planet. Scientists project that climate change will make some of these extreme weather events more likely to occur and/or more likely to be severe.

Trends in Specific Extreme Weather Events

Learn more by clicking on each tab below:

Heat Waves

  • Why does it matter? Heat waves can have serious health consequences, particularly for older adults, young children, the poor, and people with certain pre-existing health conditions, like asthma or heart disease.[1] Excessive heat can also kill or injure crops and livestock, and it can lead to power outages as heavy demand for air conditioning strains the power grid.
  • How does it relate to climate change? Even a small rise in average temperature brought on by climate change can boost the odds of extreme heat and heat waves.
  • What's happening? Climate change has increased the likelihood of more frequent and more severe heat waves. Heat waves have generally become more frequent and intense across the United States in recent decades, particularly in the western United States (including Alaska).[1] The impacts of heat waves are greatest in the Northeast and Midwest,[2] and in urban areas, where the urban heat island effect increases vulnerability to heat-related health impacts.
  • What's ahead? Heat waves are expected to become more frequent, longer, and more intense in the years ahead.[2] The number of extremely hot days is projected increase throughout the United States.[1]
  • How sure is the science? Scientists are highly confident[2] that heat waves and other extreme heat events have and will continue to become more frequent and intense due to climate change.

Adaptation: Reducing the Threat of Climate Change and Preparing for Impacts

Extreme weather and climate events pose a serious threat to the health and welfare of American families and businesses. For instance, between 2011 and 2013, the United States experienced 32 weather events that each caused at least one billion dollars in damages.[7] 2012 ranks as 2nd costliest year on record, with more than $110 billion in damages.

Map showing billion dollar weather/climate disasters in the United States from 1980 to 2012, from a minimum of 1 (Hawaii) to a maximum of 54 (Texas).This map summarizes the number of times each state has been affected by weather and climate events over the past 30 years that have resulted in more than a billion dollars in damages. The Southeast has been affected by more billion-dollar disasters than any other region. The primary disaster type for coastal states such as Florida is hurricanes, while interior and northern states in the region also experience sizeable numbers of tornadoes and winter storms. For a list of events and the affected states,
see: http://www.ncdc.noaa.gov/billions/events
Source: USGCRP (2014) Billion Dollar Weather/Climate Disasters.

EPA is taking a number of common-sense actions to reduce greenhouse gas emissions and help cities and towns build more resilient communities to prepare for the impacts of a changing climate, including the weather extremes described above.

For more information about climate adaptation and things you can do to prepare for changes in extreme weather events, see Climate Change Adaptation.

For more information on how you can reduce greenhouse gas emissions at home, on the road, and in your workplace, see What You Can Do.

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[1] USGCRP (2014). Melillo, Jerry M., Terese (T.C.) Richmond, and Gary W. Yohe, Eds. Climate Change Impacts in the United States: The Third National Climate Assessment. U.S. Global Change Research Program, 841 pp. 

[2] US EPA (2006). Excessive Heat Events Guidebook.

[3] CCSP (2008). Weather and climate extremes in a changing climate. Synthesis and Assessment Product 3.3.

[4] US EPA (2014). Climate Change Indicators in the United States.

[5] AMS (2013). Kunkel, K.E., T.R. Karl, H. Brooks, J. Kossin, J. Lawrimore, D. Arndt, L. Bosart, D. Changnon, S.L. Cutter, N. Doesken, K. Emanuel, P.Ya. Groisman, R.W. Katz, T. Knutson, J. O'Brien, C. J. Paciorek, T. Peterson, K. Redmond, D. Robinson, J. Trapp, R. Vose, S. Weaver, M. Wehner, K. Wolter, and D. Wuebbles. 2013. Monitoring and understanding changes in extreme storm statistics: State of knowledge. Bulletin of the American Meteorological Society 94:499-514.

[6] NOAA (2013). Smith, A.B., and R.W. Katz. 2013. U.S. billion-dollar weather and climate disasters: Data sources, trends, accuracy and biases. Natural Hazards 67:387-410.

[7] NOAA (2013). Billion-Dollar Weather and Climate Disasters. National Oceanic and Atmospheric Administration, National Climatic Data Center.

[8] IPCC (2013). Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change [Stocker, T.F., D. Qin, G.-K. Plattner, M. Tignor, S.K. Allen, J. Boschung, A. Nauels, Y. Xia, V. Bex and P.M. Midgley (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA, 1535 p.

[9] NOAA (2013). Historical records and trends. National Oceanic and Atmospheric Administration, National Climatic Data Center.

[10] IPCC (2012). Managing the risks of extreme events and disasters to advance climate change adaptation. Cambridge, UK: Cambridge University Press.

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