A Perspective on Understanding Changes in Weather and Climate Extremes

1. A Perspective on Understanding Changes in Weather and Climate Extremes Plant Sector Workshop March 21, 2012 Thomas R. Karl Director, National Climatic Data Center

2. Outline • Motivation • Billion-dollar Disasters • State of the Science • Heat and Cold Waves • Precipitation/flooding and drought • Snowstorms • Tornadoes • Summary

3. Billion-Dollar Weather and Climate Disasters 2011 Three more in 2011 approaching $1B Late-October Northeast winter storm April 19-20 Midwest and Southeast tornadoes August 18-21 Midwest and East high wind & hail NOAA/NCDC

4. Billion-Dollar Weather and Climate Disasters • Since 1980, 114 billion-dollar weather and climate disasters in U.S. • Total losses since 1980 of billion-dollar disasters exceed $800 billion. • Is the U.S. becoming more exposed and/or sensitive to severe events? A Record 14 Disasters in the U.S. in 2011 Three more approaching $1B NOAA Billion-Dollar Disasters http://www.ncdc.noaa.gov/oa/reports/billionz.html

5. Status of Present Knowledge • Monitoring and Understanding Changes in Extreme Storm Statistics: State of Knowledge - Kunkel, K.E. et al. (23 others). In Review (BAMS). • Monitoring and Understanding Changes in Heat Waves, Cold Waves, Floods and Droughts in the United States: State of Knowledge - Peterson, T.C. et al. (27 others). In Review (BAMS). • Monitoring and Understanding Changes in Extreme Winds, Waves, and Extratropical Storms along the Coasts: State of Knowledge - Vose, R.S. et al. (25 others) To be submitted (BAMS).

6. Status of Present Knowledge

7. Heat Waves/Cold Waves in the U.S.(Observations) Percent of the U.S. with much above or below normal temperature Extremes in Maximum Temperature Extremes in Minimum Temperature NOAA U.S. Climate Extremes Index http://www.ncdc.noaa.gov/extremes/cei/

8. U.S. Annual Maximum & Minimum Temperatures Percent of the U.S. much below normal Percent of the U.S. much above normal Maximum Temperature: not statistically significant Maximum Temperature: statistically significant decrease (0.05) (0.01 nearly) Minimum Temperature: statistically significant increase (0.05; 0.01 nearly) Minimum Temperature: statistically significant decrease (0.001) Katz, R. W., Unpublished results, 2012.

9. Heat and Cold Waves(Mean Daily Temperature) • Coldest air masses in North American source regions are warming on multi-decadal timescales (Kalkstein et al. 1990; Hankes and Walsh 2011) • Depending on the index used, differing conclusions about sub-continental statistical significance of change in heat/cold extremes Decadal average values of heat waves (red bars) and cold waves (blue bars) indices for spells of 4-day duration exceeding the threshold for a 1-in-5-year recurrence. Adapted from Peterson, T.C. et al., 2012 (In Review). Monitoring and Understanding Changes in Heat Waves, Cold Waves, Floods and Droughts in the United States: State of Knowledge. BAMS.

10. “Normalized” Temperature DistributionNorthern Hemisphere Land - Jun-Jul-Aug (1951-1980 Base Period) “Normalized” Departures Hansen, J. et al., 2012 (submitted). Public Perception of Climate Change and the New Climate Dice. Proceedings of the National Academy of Science.

11. 1-Day Heavy Precipitation Events Percent of the U.S. with much above normal 1-day heavy precipitation (>50.8mm) Annual (Jan-Dec) 1910-2011 • A statistically significant increase in extremes NOAA U.S. Climate Extremes Index http://www.ncdc.noaa.gov/extremes/cei/

12. Extreme Precipitation Extreme Precipitation Frequency Index Difference (Percent) Precipitable Water Difference(Percent) All changes positive Differences between two periods (1990-2009 minus 1971-1989) for daily, 1-in-5yr extreme events and coincident (spatial and temporal) precipitable water values Adapted from Kunkel, K.E. et al., 2012 (In Review). Monitoring and Understanding Changes in Extreme Storm Statistics: State of Knowledge. BAMS.

13. Flooding and Precipitation Trends in Total Annual Precipitation: 1909-2008 85-127 years ending 2008 River-Flow Trends in Annual Maximum Difference in Number of Months with Moderate to Extreme Drought 85-127 years ending 2008 • Regional similarities between trends of annual precipitation, droughts, and extremes of river flooding • Regional similarities between extremes of river flooding and extremes of precipitation is not as congruent Peterson, T. C. et al., 2012 (In Review). Monitoring and Understanding Changes in Heat Waves, Cold Waves, Floods and Drought in the United States: State of Knowledge. BAMS.

14. Drought Widespread persistent drought • 1930s (Central and Northern Great Plains, Northwest, Great Lakes) • 1950s (Southern Plains, Southwest), 1980s (West, Southeast) • First decade of the 21st century (West, Southeast) Trends (% per century) • 1900 to 2011: -0.1% • 1930 to 2011: -10.0% • 1971 to 2011: +31.6% Peterson, T. C. et al., 2012 (In Review). Ibid.

15. Projected Change (A2 Scenarios – “Higher Emissions”) in North American Precipitation (Late 21st Century) 15 Climate Models Global Climate Change Impacts in the United States, Thomas R. Karl, Jerry M. Melillo, and Thomas C. Peterson, (eds.). Cambridge University Press, 2009.

16. Combined Drought Severity and Water Surplus NOAA U.S. Climate Extremes Index http://www.ncdc.noaa.gov/extremes/cei/

17. Extreme Snowstorms Temperature Anomalies During Season of Extreme Events Most severe storms for each of the six climate regions from 1900 to 2010 • For the storms of record, the average temperature was below normal for each region • Every region had two of the five storms of record occurring during seasons with above average temperatures Frequency Precipitation Anomalies During Season of Extreme Events • Number of extreme snowstorms (upper 10 percentile) occurring each decade within the six U.S. climate regions in the eastern two-thirds of the contiguous U.S. Precipitation (Average Anomalies) 8% -9% 19% -1% 5% -6% Kunkel, K.E., et al., 2012 (In Review). BAMS.

18. Tornadoes & Convective Storms U.S. Annual Tornadoes • Although some ingredients that are favorable for severe thunderstorms have increased over the years, others have not • Overall, changes in the frequency of environments favorable for severe convective storms have not been statistically significant Kunkel, K.E., et al., 2012 (In Review). BAMS.

19. Tornadoes & Convective Storms • For continental U.S. severe tornadoes (L≥10 km), (top) total path length per year, and (bottom) the number per year r² = 0.1269 Length per year (km/yr) r² = 0.27 Number per year Malamud, B. D.and D. L. Turcotte,2012. Statistics of severe tornadoes and severe tornado outbreaks. Atmos. Chem. Phys. Discuss.

20. Tornadoes & Convective Storms Wind Shear vs. Vertical Velocity–6km proximity values Each cell is best viewed as a conditional probability Kunkel, K.E., et al., 2012 (In Review). BAMS.

21. Summary • Widely varying suitability of our data and physical understanding of various extreme events Adapted from Lubchenco, J., and T. Karl, 2012. Predicting and managing extreme weather events. Physics Today.

22. Questions?