NOAA 31st Climate Diagnostics and Prediction Workshop Boulder, Colorado October 25 2006

1. Challenges in Attribution of Climate Variability and Trends NOAA 31st Climate Diagnostics and Prediction Workshop Boulder, Colorado October 25 2006

2. Popular Views On Attribution

3. Popular Views On Attribution

4. Popular Views On Attribution

5. What is Attribution? • Attribution is the action of ascribing a known condition to a particular source or sources. • Attribution is the process of establishing cause and effect. • Attribution science involves the comprehensive explanation of current and evolving • climate conditions…both variability and change, • Attribution seeks to explain the role of forcings…both natural and anthropogenic. • Attribution includes the explanation of climate predictions…their success and failure.

6. Why is Attribution Important?

7. Why is Attribution Important? In Spring 2006, the Senate Commerce Disaster Prevention and Prediction Subcommittee requested NOAA to explain the very warm and evolving drought conditions in the West.

8. Why is Attribution Important?

9. Why is Attribution Important?

10. Why is Attribution Important?

11. Why is Attribution Important? US House Committee on Science met 7 October 2005 to have NOAA explain its prediction of hurricanes.

12. Current Attribution Challenges • Why has there been a recent increase in Atlantic hurricane activity?

13. Current Attribution Challenges • Why has there been a recent increase in Atlantic hurricane activity?

14. Current Attribution Challenges • How do we explain the 2006 hurricane predictions?

15. Current Attribution Challenges • How do we explain the 2006 hurricane predictions? Predictions of tropical activity in the 2006 season Source Date Named storms Hurricanes Major hurricanes CSU Average (1950–0) 9.6 5.9 2.3 NOAA Average10 6 2 Record high activity 28 15 8 Record low activity 420 CSU 5 December 2005 17 9 5 CSU 4 April 2006 17 9 5 NOAA 22 May 2006 13–16 8–10 4–6 CSU 31 May 2006 17 9 5 CSU 3 August 2006 15 7 3 NOAA 8 August 2006 12–15 7–9 3–4 CSU 1 September 2006 13 5 2 CSU 3 October 2006 11 6 2 Activity to date952

16. Current Attribution Challenges • How do we explain the regionality and the seasonality of US sfcT trends ?

17. Current Attribution Challenges • How do we explain the regionality and the seasonality of US sfcT trends ?

18. Current Attribution Challenges • How do we explain the regionality and the seasonality of US sfcT trends ?

19. Current Attribution Challenges • How do we explain the long-lead seasonal outlooks?

20. Current Attribution Challenges • How do we explain the long-lead seasonal outlooks?

21. Current Attribution Challenges • Is the risk of drought now increasing, and if so, why?

23. Drought Statistics: 1895-1950 Average Duration of PDSI<-3 Areal-Coverage of PDSI<-3

24. Drought Statistics: 1951-2005 Average Duration of PDSI<-3 Areal-Coverage of PDSI<-3

25. Explaining Changes in Extreme US Climate Events…….Jerry Meehl • Explaining US Precipitation and Temperature Trends….Imke Durre • Explaining Origins of North American Drought………….Richard Seager • Explaining Increases in Atlantic Hurricane Activity……Kevin Trenberth Overarching Challenge: Given the public perception of climate change and an increase in extreme events (e.g. droughts, heat waves, hurricanes), how well is our science community positioned to provide critical decision support information (e.g., answer to the questions what happened, why it happened, and what is likely to happen next) needed for planners to make decisions and manage risk?

26. Overarching Challenge: Given the public perception of climate change and an increase in extreme events (e.g. droughts, heat waves, hurricanes), how well is our science community positioned to provide critical decision support information (e.g., answer to the questions what happened, why it happened, and what is likely to happen next) needed for planners to make decisions and manage risk? Q1 What attribution questions are of high relevance to decision makers, e.g., in water resources planning, agriculture, energy, and policy making for sustainable development?

27. Overarching Challenge: Given the public perception of climate change and an increase in extreme events (e.g. droughts, heat waves, hurricanes), how well is our science community positioned to provide critical decision support information (e.g., answer to the questions what happened, why it happened, and what is likely to happen next) needed for planners to make decisions and manage risk? Q2 What is the contribution of natural variability to the U.S. warming since 1970s?

28. Overarching Challenge: Given the public perception of climate change and an increase in extreme events (e.g. droughts, heat waves, hurricanes), how well is our science community positioned to provide critical decision support information (e.g., answer to the questions what happened, why it happened, and what is likely to happen next) needed for planners to make decisions and manage risk? Q3 What is the explanation for regionality and seasonality of US temperature trends since the 1970s?

29. Overarching Challenge: Given the public perception of climate change and an increase in extreme events (e.g. droughts, heat waves, hurricanes), how well is our science community positioned to provide critical decision support information (e.g., answer to the questions what happened, why it happened, and what is likely to happen next) needed for planners to make decisions and manage risk? Q4 What is the documented evidence for trends in climate extremes over the US?

30. Overarching Challenge: Given the public perception of climate change and an increase in extreme events (e.g. droughts, heat waves, hurricanes), how well is our science community positioned to provide critical decision support information (e.g., answer to the questions what happened, why it happened, and what is likely to happen next) needed for planners to make decisions and manage risk? Q5 How do we explain the successes and failures of individual climate forecasts?

31. Overarching Challenge: Given the public perception of climate change and an increase in extreme events (e.g. droughts, heat waves, hurricanes), how well is our science community positioned to provide critical decision support information (e.g., answer to the questions what happened, why it happened, and what is likely to happen next) needed for planners to make decisions and manage risk? Q5 What is the reason for the controversy in explaining Atlantic Hurricane variability?