Ahira Sánchez-Lugo October 20, 2015 NOAA’s National Centers for Environmental Information

2  Understanding and knowledge on: What is extreme weather? Relationship between climate change and extreme weather What are the expected and observed changes in extreme weather

°F

4 ©The COMET Program

5  On August 20, 1983 the maximum temperature was 99°F.  It depends! Weather that lies outside a location’s normal range of weather intensity. It will depend on what a location is used to experiencing and what it is prepared for.

6

7  Extremes can have an impact on our health  It has a strong effect on our economy by influencing: Agriculture Energy Use Water Resources  Understanding extremes can help us better prepare for them.

 We are more likely to be resilient to weather and climate extremes as we acclimate to the historical range of extremes. ©The COMET Program

 Observations show Earth’s temperature is increasing.  The warming is caused by increasing greenhouse gas emissions from human activities.

Wilder Weather Changing Rain and Snow Patterns Higher Temperatures Increased Drought

11 ©The COMET Program

12 ©The COMET Program

Light and moderate rains are being replaced by more heavy rain events.

1961– –2010

 Climate variability modes help enhance or suppress extreme events. La Niña increases (decreases) tropical cyclone activity in the Atlantic (North East Pacific) El Niño decreases (increases) tropical cyclone activity in the Atlantic (North East Pacific)

Short and simple answer: NO  Climate variability continues to play a key role in extreme weather  However, climate change has shifted the odds and changed the natural limits.

 Greenhouse gases have a similar impact to steroids in a baseball player.  Steroids increase the chances of hitting a home run, but don’t guarantee that each home run was caused by steroid use.

Wilder Weather Changing Rain and Snow Patterns Higher Temperatures Increased Drought

 Extreme events are born from a set of ingredients. Hurricane:  Warm ocean water (temperature of 80°F or greater)  Form between 5° to 20° latitude  Lots of moisture in the air  Light winds throughout the troposphere (the lowest layer of Earth’s atmosphere and where all weather occurs)  An area of low pressure

21

22

 Expected change: More intense, frequent, and longer-lasting.  Observed change: The U.S. is observing warmer minimum & maximum temperatures throughout the year.

 Expected change: Will still occur, but will be less frequent.  Observed change: The U.S. has had fewer unusually cold days.

 Expected change: An increase in the intensity. Light precipitation will decrease.  Observed change: The largest increases in heavy precipitation occurred in the Northeast and Midwest.

 Expected change: Likely to become more frequent and severe in some regions.  Observed change: Increasing temperatures have made droughts more severe and widespread in the Western U.S. in recent decades.

 Expected change: Expect TCs to become more intense. However, it is uncertain if they will become more frequent.  Known fact: Sea level is rising, making the impact of a TC potentially more destructive. Hurricane Sandy (2012)

 Expected change: Uncertain. We do expect a warmer, moister environment, which is conducive to more severe thunderstorms.

29  Climate change affects weather outcomes by changing the frequency and nature of how ingredients come together  We are seeing changes in certain types of extreme weather We expect an increase in frequency and intensity:  Heat Waves  Heavy downpours/flooding  Drought We expect a decrease to cold events

NOAA’s National Centers for Environmental Information