1. Northern Hemisphere Climate Variability over the Past Few Hundred Years: Proxy-based Reconstructions of the winter NAM and PNA Justin J. Wettstein John M. Wallace justinjw@atmos.washington.edu Climate Impacts Group Seminar January 4 th, 2005

2. N.H. Climate Variability over the Past Few Hundred Years: NAM/PNA Reconstructions OUTLINE NAM ? PNA ? Existing Proxy-based Reconstructions A more parsimonious approach Where from here?

3. NAM ? PNA ?

4. N.H. Climate Variability over the Past Few Hundred Years: NAM/PNA Reconstructions Northern Annular Mode (NAM) Pacific North America [pattern] (PNA) PNA: Sea Level Pressure NAM: Sea Level Pressure Max in both figures is ~6 millibars per unit change in the NAM / PNA index

5. N.H. Climate Variability over the Past Few Hundred Years: NAM/PNA Reconstructions NAM: Temperature / Precipitation 1 Max is ~1.8º C per unit change in NAM Max is ~1 cm/month per unit change in NAM Temperature (red = warm) Precipitation (red = dry)

6. N.H. Climate Variability over the Past Few Hundred Years: NAM/PNA Reconstructions NAM: Temperature / Precipitation 2 Max is ~1.8º C per unit change in NAM Max is ~1 cm/month per unit change in NAM Temperature (red = warm) Precipitation (red = dry)

7. N.H. Climate Variability over the Past Few Hundred Years: NAM/PNA Reconstructions PNA: Temperature / Precipitation ~ -1.5 to 0.6ºC per unit change in PNA Max is ~1 cm/month per unit change in NAM Temperature (red = warm) Precipitation (red = dry) Flip sign: sorry!

8. N.H. Climate Variability over the Past Few Hundred Years: NAM/PNA Reconstructions Time Series of the NAM / PNA

9. Existing Proxy-based Reconstructions

10. N.H. Climate Variability over the Past Few Hundred Years: NAM/PNA Reconstructions Proxies with annual resolution Source: International Tree Ring Database (various) Source: NOAA Paleoclimatology Program (various)

11. N.H. Climate Variability over the Past Few Hundred Years: NAM/PNA Reconstructions NAO Reconstructions: Summary [Jones and Mann, 2004 (Reviews of Geophysics: Fig 6b)] Jones+ 1997: Observed NAO (1821-Present) Luterbacher+ 2002: Multi-proxy, documentary records, met data (1500-1990) Cook+ 2002: Multi-proxy (1400-1979) Vinther+ 2003: Greenland ice cores (1250-1970) Others: Appenzeller+ (1998), Gluek and Stockton (2001), Cullen+ (2001)

12. N.H. Climate Variability over the Past Few Hundred Years: NAM/PNA Reconstructions NAO Reconstruction: 1 example Cook et al., 2002 (J. Climate)

13. N.H. Climate Variability over the Past Few Hundred Years: NAM/PNA Reconstructions Cook et al., 2002: Proxy weights

14. N.H. Climate Variability over the Past Few Hundred Years: NAM/PNA Reconstructions PNA-like Reconstruction Moore et al., 2002 (Nature) See also: Minobe, 1997 (GRL) Accumulation vs. time at site

15. N.H. Climate Variability over the Past Few Hundred Years: NAM/PNA Reconstructions PDO reconstruction: example(s) Biondi et al., 2001 (J. Climate) Others: Gedalof and Smith, 2001Evans et al., 2000 Urban et al., 2000Linsley et al., 2000

16. N.H. Climate Variability over the Past Few Hundred Years: NAM/PNA Reconstructions PDO meta-reconstruction: example Gedalof et al., 2002 (GRL) PC-based reconstruction of the PDO index using 5 existing reconstructions PC1 kept, PDO correlation is 0.64 from ~1900 - 1990 “PDO may not have been an important organizing structure during the 19 th century” SST regression

17. A more parsimonious approach

18. N.H. Climate Variability over the Past Few Hundred Years: NAM/PNA Reconstructions Approach 1. Species-by-species 2. Trees must lie in a region where the temperature and/or precipitation signal of the NAM / PNA is robust 3. Growth of a particular species must be significantly and consistently related to temperature or precipitation during the winter preceding the annual growth ring 4. Ring width time series must be available 1711-1971 so only one statistical model is required 5. Each candidate predictor must add to both the calibration and cross-validated skill of the model, or it is removed

19. N.H. Climate Variability over the Past Few Hundred Years: NAM/PNA Reconstructions Good locations: NAM temperature

20. N.H. Climate Variability over the Past Few Hundred Years: NAM/PNA Reconstructions Good locations: NAM precipitation

21. N.H. Climate Variability over the Past Few Hundred Years: NAM/PNA Reconstructions Bad locations

22. N.H. Climate Variability over the Past Few Hundred Years: NAM/PNA Reconstructions Prior winter proxy skill: monthly Black Pine: Mediterranean Temperature (good proxy) Norway Spruce: Mediterranean Temperature (poor proxy)

23. N.H. Climate Variability over the Past Few Hundred Years: NAM/PNA Reconstructions Poor seasonal correlations: 2 ex. Scots Pine Minimum Density temperature correlation Camp century temperature correlation

24. N.H. Climate Variability over the Past Few Hundred Years: NAM/PNA Reconstructions Depends on where you look Norway Spruce Temp. CorrelationNorway Spruce Precip. Correlation

25. N.H. Climate Variability over the Past Few Hundred Years: NAM/PNA Reconstructions Good seasonal correlations Good trees / ring widths (temperature examples) milcent Good ice core (temperature)

26. N.H. Climate Variability over the Past Few Hundred Years: NAM/PNA Reconstructions Summary of results

27. Where from here?

28. N.H. Climate Variability over the Past Few Hundred Years: NAM/PNA Reconstructions Frequency dependent 1

29. N.H. Climate Variability over the Past Few Hundred Years: NAM/PNA Reconstructions Frequency dependent 2 correlationcorrelation

30. N.H. Climate Variability over the Past Few Hundred Years: NAM/PNA Reconstructions Future Work 66 annually-resolved records from ice cores – Local temperature correlations up to 0.55 – Local precipitation correlations up to 0.55 – NAM index correlations up to 0.55 – PNA index correlations up to 0.60 – Best correlations generally from low-pass filtered ice data – Possibility to “staple” two reconstructions together? Match cross-validation method to Cook et al., 2002 and compare with NAO reconstruction directly – Simplified NAM and PNA (not shown) reconstructions seem comparable to existing literature (x-valid r’s ~0.65 and ~0.60) Other suggestions?