1 / 36

Climate Change ???

Climate Change ???. How Is it Detected?. Difficulties of Detecting Climate Change. Climate systems are intrinsically noisy The climate system is not well sampled Insufficient temporal baseline to determine proper amplitude of “natural” variations

varuna
Télécharger la présentation

Climate Change ???

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Climate Change ??? How Is it Detected?

  2. Difficultiesof Detecting Climate Change • Climate systems are intrinsically noisy • The climate system is not well sampled • Insufficient temporal baseline to determine proper amplitude of “natural” variations • Which recording sties are best tracers of climate change? • What indicators are best tracers of climate change?

  3. Statistics of Extreme Events

  4. Pacific Northwest Climate Change • Real or is it just our imagination? 1998 Official Climatology Statement It appears that Oregon is poised for a relatively warm, dry winter, after three years of cooler, wetter winters. That does not mean a return to drought conditions. In fact, the evidence suggests the PNW is in for a long period of cold and wet.

  5. Reduced snow pack effects regional power generation; 2001 drought resulted in 46% price hike by BPA Reduced soil moisture in the Cascades elevates the risk of catastrophic forest fires CentralQuestion: Is the PNW getting warmer and drier?

  6. Proposition to Prove: The PNW is getting warmer and drier

  7. The Physics of Climate Change

  8. Astrophysics and Climatology? • Digging signal out of noisy data constitutes most of observational astrophysics. Why not apply similar techniques (e.g. large scale smoothing, waveform analysis, etc) to climate data.

  9. The PNW Climate Waveform? Y-axis is in units of standard deviation

  10. PNI Questions: • Are the “features” significant? (remember Y-axis units are in standard deviations) • Is the PNI a fluke? • Is their bias due to incomplete sampling? • PNI and Fish Counts

  11. Mid Century World Wide Cooling • May be reflected in the PNI?

  12. A Tale of Two Jets

  13. Decadal Jet Stream Variations? • Physical Cause? • ENSO (El Nino) • PDO (Pacific Decadal Oscillilation) • NPI (North Pacific Index) • Other?

  14. ENSO • Really has the wrong waveform • Amplitude variations occur on more rapid timescales (3-5 years)

  15. PDO • First Discovered in 1996 • 6-18 month persistence of temperature anomalies • Unknown cause

  16. NPI • Area weighted sea level pressure over the Gulf of Alaska

  17. Combined PDO + ESNO Does Matter

  18. The basic issue is whether or not the cyclical behavior seen in the last century will continue into this one. We will show later that the PNI shows no sign of returning to the cool/wet cycle, even though its statistical time has arrived to do so.

  19. Waveform Example

  20. Testing the Robustness of the PNI • Can the PNI be broadly reproduced by randomly selecting sites? • Does the PNI have a primary driver – rain, snow, temperature? • If the PNI can be reproduced (and is therefore not a fluke of these 3 sites) can we fit the time series to make a prediction about future climate?

  21. Calibration Check

  22. Using Annual Snowfall

  23. On Robustness • Several thousand trials were run to randomly select sites and construct individual site specific indices to compare against the original PNI. • In all cases one can recover the basic PNI waveform, although there are amplitude differences • Conclude that the PNI waveform is real and does represent climate West of the Cascades

  24. Rain, Temp or Snow? Temp shows most variation; followed closely by snow; Cool/wet periods are best defined by temp + snow;

  25. Reconstructing the Time Series Fundamental Period = 53 years

  26. Fundamental (53)+Secondary (13)

  27. 3 component Fit In 1998, we should have started back into the cold and wet cycle

  28. Eugene Rainfall 1960-1998 50.1 (mean) 9.4 (sd) 1.3 (m.e.) Eugene Rainfall 1999-2004 36.7 5.6 2.5 Recent Data inconsistent with return to cool/wet cycle Z-statistic is 4.8 (1 in 1,000,000 change of being random) 2001 Annual rain lowest in last 60 years 2005 Rain to date lower than 2001

  29. Reduced Snowfall

  30. Local Manifestation of Reduced Snow Pack http://climate.ntsg.umt.edu/html/science_western_water.pdf

  31. Conclusions: • The PNI is robust and recoverable from analysis of many random sites • PNI amplitude is exaggerated by use of March 15 snowfall instead of annual snowfall • Statistical pattern suggests we should now be in the middle of a cool/wet cycle; empirical data (still limited of course) argues otherwise

  32. Human Implications of This Climate Change • Decreased power production from hydroelectric dams due to lower snow packs. RATES will rise. • Don’t own a ski resort • Longer and likely more severe forest fire seasons • Continued milder winters might produce less weather related accidents

  33. The End

More Related