Interannual Temperature Variations

1. Interannual Temperature Variations By Anthony R. Lupo Department of Soil, Environmental, and Atmospheric Science 302 E ABNR Building University of Missouri Columbia, MO 65211

2. Interannual Temperature Variations • General Outline: • Causes of interannual and interdecadal global temperature variations. • Some real results from the midwest USA. (acknowledgement: K. Birk, 2006) • Interannual variability and climate change.

3. Interannual Temperature Variations • The Earth’s climate (as part of the Earth – Atmosphere System) is generally considered to be a boundary – value problem. The earth-atmosphere system, courtesy of Dr. Richard Rood. (http://aoss.engin.umich.edu/class/aoss605/lectures/)

4. Interannual Temperature Variations • On the time-scale of a year to a decade, the dominant phenomenon in the climate system is the El Niño and Southern Oscillation (and the SST variations that accompany it) (e.g. Mokhov et al. 2004)

5. Interannual Temperature Variations • The El Niño cycle has been known for some time by the scientific community (e.g., Sir Gilbert Walker), and impacts the global weather beyond the tropical Pacific.

6. Interannual Temperature Variations • From Lupo et al. 2007 (monthly temperatures over a 50 year period)

7. Interannual Temperature Variations • Power spectra of that same temperature record (cycles per decade)

8. Interannual Temperature Variations • ENSO impacts the position of the jet stream and other phenomena which impact the temperatures on the time-scale of seasons (e.g. via blocking – Wiedenmann et al. 2002; or the MJO – e.g. Mo, 1999, 2000)

9. Interannual Temperature Variations • ENSO will impact the mean position and strength of general circulation features such as the Indian Monsoon, the Tropical Atlantic Trough (which impacts hurricane frequency and strength in the Atlantic – e.g. Gray, 1984; Lupo et al. 2008) • All these will have an impact on the number and strength of extreme weather (warm and cold) within seasons, and numerous studies show this.

10. Interannual Temperature Variations

11. Interannual Temperature Variations • There are other factors that may influence ENSO (e.g. Landscheidt uses the polarity of the Earth’s magnetic field to predict ENSO. • Further, there are studies that indicate that interannual variability (as related to ENSO) can be modulated or tempered by interdecadal variability (e.g. PDO, solar forcing, etc).

12. Interannual Temperature Variations • Study Region (Birk - 2006) (data gathered from 1900 – 2005 – where possible)

13. Interannual Temperature Variations • Minneapolis, MN: ENSO variability changes from north to south across our region. ENSO variability stronger in PDO 1 phase (north).

14. Interannual Temperature Variations • Fayetteville, AR: ENSO variability changes from north to south across our region. ENSO variability not stronger in either phase.

15. Interannual Temperature Variations • El Niño winter (1997) La Niña winter (1971) • (2 major blocking) (4 major blocking )

16. Interannual Temperature Variations • Recently, Zorita et al. 2008 use statistical analysis and conclude that it is highly improbable that the last 10 – 20 years of the global data set should contain the warmest years. • They first assumed a stationary climate and then used two autoregressive models, one including long term variability, the other using short term variability.

17. Interannual Temperature Variations • They also conclude that this is indicative of the anthropogenic forcing since the probability is very low that nature could produce so many warm years at the end of a data set. • Here, a simple model of the global temperatures since the mid-to-late 1800’s is built using three simple functions which are in phase with, or mimic, what could be natural variations and demonstrate that the latest years in the data set could easily be the warmest.

18. Interannual Temperature Variations • This analysis does not invoke statistical analysis, nor do we claim here to provides a physical explanation for the global temperature record, or models the physics realistically, it is for demonstration purposes! • A more complete and similar model can be found in Klyshtorin and Lybushkin (2003, 2007) • From K. Birk (2006) (paper in preparation)

19. Interannual Temperature Variations FIG. 2.1. Annual global surface temperature departures from the 1961 to 1990 average. [Sources: NOAA/ NCDC; CRU/UKMO (HadCRUT3); and NASA GISS.] (From BAMS, July 2008)

20. Interannual Temperature Variations • Natural Forcing 1 (solar? coming out of the little ice age? Something yet to be discovered?) Linear trend at the rate of 2 units per 125 time units.

21. Interannual Temperature Variations • Natural Forcing 2 (oceans? Pacific Decadal Oscillation? NAO? AMO? – here amplitude 1 unit and period of 62.5 years)

22. Interannual Temperature Variations • Natural Forcing 3 (oceans? ENSO? – here amplitude 1 unit and period of ~6.0 years – similar to that found by Birk, 2006)

23. Interannual Temperature Variations • Natural Forcing 1+2+3 (where do you think the five warmest years will be?)

24. Interannual Temperature Variations • Summary and Conclusions: • The interannual variation in global temperatures is likely dominated by the El Nino Cycle. These have an impact on regional climates worldwide. • The strength of the ENSO cycle is modulated by other natural cycles, on both longer and shorter time-scales.

25. Interannual Temperature Variations • Summary and Conclusions: • In the midwestern USA, our research demonstrates that the Pacific Decadal Oscillation modifies the strength of the ENSO cycle. • It is likely that interannual and interdecadal cycles as forced by natural processes will continue to occur regardless of how the climate changes

26. Interannual Temperature Variations • Summary and Conclusions: • It is easy to demonstrate that the fact that the warmest years in the global observed record have occurred recently can be explained without needing to invoke statistical arguments.

27. Interanual Temperature Variations • Questions? • Comments? • Criticisms? • LupoA@missouri.edu