The Climate Extremes Index: A Southeast U.S. Perspective

1. The Climate Extremes Index: A Southeast U.S. Perspective Karin L. Gleason Meteorologist Climate Monitoring Branch NOAA/NESDIS/National Climatic Data Center Asheville, NC Carolinas and Virginia Climate Conference Wilmington, NC October 20-21, 2009

2. The Climate Extremes Index: A Southeast U.S. Perspective - Overview - • History of the Climate Extremes Index (CEI) • Operational Contiguous U.S. (CONUS) CEI and results • Trends in national/regional temperature and precipitation • Compare/Contrast CONUS CEI with Southeast (SE) Region CEI results • Summary/Conclusions Carolinas and Virginia Climate Conference Wilmington, NC October 20-21, 2009

3. The Climate Extremes Index: A Southeast U.S. Perspective - History of the Climate Extremes Index (CEI) - • First introduced in 1996 (Karl et al.) to quantify observed changes in climate within the CONUS • General lack of observational data on extremes • Provided a means to communicate with policy makers regarding our understanding of changes in climate • The Climate Extremes Index (CEI) was developed as a “first-glance” monitoring tool to help identify possible trends in a variety of climate extremes indicators • Originally looked at historical data (1+ years old) on an annual basis Carolinas and Virginia Climate Conference Wilmington, NC October 20-21, 2009

4. The Climate Extremes Index: A Southeast U.S. Perspective - History of the Climate Extremes Index (CEI) – cont’d • CEI is comprised of five indicators which illustrate possible extremes in: • - monthly mean maximum and minimum temperature • - extreme 1-day precipitation • - the number of days with/without precipitation • - the Palmer Drought Severity Index (PDSI) • “Extremes” are defined as occurrences much above/below normal (outside the 90th/10th percentile value) over the period of record – therefore expected extremes average is 20% • The area of the CONUS with extreme conditions is compared with the remainder of the CONUS to yield an extreme fraction for a given period • The CEI has been updated to include a tropical system component and is calculated for multiple seasons and on an operational basis (updated monthly) • Additions and modifications to original index are explained in “A Revised U.S. Climate Extremes Index” (Gleason et al. 2008) Carolinas and Virginia Climate Conference Wilmington, NC October 20-21, 2009

5. The Climate Extremes Index: A Southeast U.S. Perspective - History of the Climate Extremes Index (CEI) – cont’d • The CEI is the arithmetic average of the following indicators of the percentage of the CONUS area: • The sum of the percentage of the CONUS with maximum temperatures (a) much below normal and (b) much above normal. • The sum of the percentage of the CONUS with minimum temperatures (a) much below normal and (b) much above normal. • The sum of the percentage of the CONUS in (a) severe drought and with (b) severe moisture surplus based on the PDSI. • Twice the value of the percentage of the CONUS with a much greater than normal proportion of precipitation derived from extreme 1-day precipitation events. • The sum of the percentage of the CONUS with a much greater than normal number of days (a) with precipitation and (b) without precipitation. • The sum of squares of CONUS landfalling tropical storm and hurricane wind velocities scaled to the mean of the first five indicators (currently experimental). • Expected (mean) value for CEI and components is 20% Carolinas and Virginia Climate Conference Wilmington, NC October 20-21, 2009

6. The Climate Extremes Index: A Southeast U.S. Perspective - Operational CONUS CEI and Results - • Noticeable/steady upward trend in CONUS CEI since about 1970 • Primarily the result of increasing extremes in max/min temperatures, 1-day precipitation and PDSI (both wet & dry) Carolinas and Virginia Climate Conference Wilmington, NC October 20-21, 2009

7. The Climate Extremes Index: A Southeast U.S. Perspective - Operational U.S. CEI and Results – cont’d 1-Day Prcp Tmax Tmin PDSI • Combined percentages for annual period show upward trend in extremes in these four indicators over the last 30+ years Carolinas and Virginia Climate Conference Wilmington, NC October 20-21, 2009

8. The Climate Extremes Index: A Southeast U.S. Perspective - Southeast Region - • Southeast Region includes: • Virginia • North Carolina • South Carolina • Georgia • Alabama • Florida (Karl and Koss, 1984) Carolinas and Virginia Climate Conference Wilmington, NC October 20-21, 2009

9. The Climate Extremes Index: A Southeast U.S. Perspective - Southeast Region versus CONUS Trends - • Temperature & precipitation trends for the SE are not as large as in other parts of the U.S. • Would expect to see fewer extremes in CEI across SE region as compared with CONUS SE Trend: +0.26°F/Century SE Trend: +1.25%/Century CONUS Trends: +1.28°F/Century +6.10%/Century Data: NCDC, Plots: EPA Period of record: 1901-2008 Carolinas and Virginia Climate Conference Wilmington, NC October 20-21, 2009

10. The Climate Extremes Index: A Southeast U.S. Perspective - Southeast Region CEI Results - • Annual: Slight upward trend from about 1950 to present in SE CEI with a lot of inter-annual variability (CONUS CEI less variable from year to year and more pronounced upward trend) • PDSI and 1-day precipitation largest contributors to increase in SE CEI trend CONUS Region Southeast Region +6%/decade over last 30 yrs +4%/decade over last 30 yrs Carolinas and Virginia Climate Conference Wilmington, NC October 20-21, 2009

11. The Climate Extremes Index: A Southeast U.S. Perspective - Southeast Region CEI Results – cont’d • Annual: Extremes in wet/dry PDSI periods as well as elevated extremes in 1-day precipitation were the only indicators with above expected extremes over the last 2-3 decades in SE. Southeast Region PDSI 1-Day Prcp Tmin Carolinas and Virginia Climate Conference Wilmington, NC October 20-21, 2009

12. The Climate Extremes Index: A Southeast U.S. Perspective - Southeast Region CEI Results – cont’d • Annual: Extremes in monthly maximum & minimum temperatures across SE appear to have transitioned from cool to warm from 1960 to present – (though little overall trend in combined percentage) Southeast Region Tmax Tmin Carolinas and Virginia Climate Conference Wilmington, NC October 20-21, 2009

13. The Climate Extremes Index: A Southeast U.S. Perspective - Seasonal CEI Results Comparisons - • Annual: US CEI temperature extremes are few in the 1960s, but show consistent increase post-1970 and tend to be warmer extremes – (steady upward trend in extremes in combined percentage) CONUS Region Tmax Tmin Carolinas and Virginia Climate Conference Wilmington, NC October 20-21, 2009

14. The Climate Extremes Index: A Southeast U.S. Perspective - Seasonal CEI Results Comparisons – cont’d - • Peak of mid-1930s drought in the High Plains didn’t include SE Southeast PDSI CONUS PDSI Carolinas and Virginia Climate Conference Wilmington, NC October 20-21, 2009

15. The Climate Extremes Index: A Southeast U.S. Perspective - Seasonal CEI Results Comparisons – cont’d - • Summer: Similar trends in extreme extent for 1-day precipitation in the CONUS and SE regions (approx. +1%/decade from the mid-70s to the present) Southeast Region CONUS Region 1-Day Prcp Carolinas and Virginia Climate Conference Wilmington, NC October 20-21, 2009

16. The Climate Extremes Index: A Southeast U.S. Perspective - Seasonal CEI Results Comparisons – cont’d - • Spring: SE CEI warm minimum temperature extremes not as extensive/consistent as CONUS CEI over last 20 years Southeast Region CONUS Region Tmin Carolinas and Virginia Climate Conference Wilmington, NC October 20-21, 2009

17. The Climate Extremes Index: A Southeast U.S. Perspective - Summary/Conclusions - • A regional CEI helps to visualize and quantify the magnitude and type of extremes which may be affecting certain parts of the country • Extremes observed across the SE Region over the last 30 years are not necessarily increasing at the same rate as those observed across the CONUS region • Timing of extreme events varies from region to region (e.g. 1930s drought) • More inter-annual variability with SE CEI as compared with CONUS CEI (and likely other regions) • Annual: SE CEI increasing but not at same rate as the CONUS CEI over last 30 years • Annual: Extremes in PDSI and 1-day precipitation are the primary contributors to an increasing SE CEI over last 20-30 years Carolinas and Virginia Climate Conference Wilmington, NC October 20-21, 2009

18. The Climate Extremes Index: A Southeast U.S. Perspective - Summary/Conclusions – cont’d - • Annual: Little overall trend in max/min temperature extremes in SE, yet evident shift from cold to warm extremes from 1960s to present • Summer: Extremes in 1-day precipitation for both CONUS and SE are increasing over the last 30 years • Summer: Extremes in minimum temperatures are on rise for both SE and CONUS regions and cool extremes dominate SE region from 1960s to 1970s • Spring: Warm minimum temperature extremes across SE not as extensive as seen across the CONUS over last 20 years Carolinas and Virginia Climate Conference Wilmington, NC October 20-21, 2009

19. The Climate Extremes Index: A Southeast U.S. Perspective - For Additional Information - • NCDC’s Climate Monitoring Branch Products: • http://www.ncdc.noaa.gov/climate-monitoring/ • The Climate Extremes Index (CEI) Web Page: • http://www.ncdc.noaa.gov/oa/climate/research/cei/cei.html • Regional CEI plots and data (for all 9 regions) will likely become operational in 2010 • Contact: Karin.L.Gleason@noaa.gov Carolinas and Virginia Climate Conference Wilmington, NC October 20-21, 2009