1. Climate Change Spring 2016 Kyle Imhoff

2. Let’s start with the big picture (climate forcings)…

3. Major Forces – Milankovitch Cycles

4. Major Forces – The Oceans

5. Major Forces – Volcanic Activity

6. Major Forces – The Sun

7. What Do We Know? 4 The previously mentioned forcing mechanisms are well-known, well- understood, and relatively accurately observed 4 These climate forcing mechanisms do not completely explain the current warming trend seen globally

8. The Greenhouse Effect..

9. Greenhouse Effect

10. Carbon Dioxide Output

11. Greenhouse Effect Courtesy of IPCC

12. Greenhouse Effect – Water Vapor

13. What Does This Mean For Global Temperatures?

14. Global Temperature Trend Courtesy of NASA Global Institute for Space Studies

15. Global Temperatures by Hemisphere

16. Comparison of Trends

17. The Hockey Stick

18. A modification of the ‘Stick’

19. Implications for the Mid-Atlantic

20. Sea Level Rise Predictions

21. Inland flooding because of increased moisture

22. So Why The Controversy?

23. Attribution and Projections 4 The actual temperatures at the surface globally are increasing – this is not in dispute scientifically 4 Why temperatures are rising is another story – “scientific consensus” is a bit misleading –Science is driven by skepticism and disproving previously held beliefs 4 The ability to quantify how much greenhouse gases (specifically CO 2 ) affect temperatures would require a nearly perfect understanding of how all other forcings affect temperatures –Very difficult to do with a high degree of confidence though datasets are getting better

24. Attribution and Projections 4 There is a statistical argument as well –We have ~150 years of GOOD meteorological observations at the surface –We can reconstruct temperatures back 1000s of years, but these are not as precise (tree rings, ice core data, etc.) –To give perspective to current warming trend is very difficult (too small of a sample size of good data) Is this warming unprecedented Has this kind of warming occurred in the past without other forcings present?

25. Attribution and Projections 4 Projection Accuracy –How accurate are climate models? –Weather models are known to have flaws/imperfections – climate models are not immune –Climate models are built to match historical information Historical information is imperfect and the future climate system may not react the way scientists think it “should” Think back to the atmosphere being a “chaotic” system by nature

26. Summary – The Three A’s.. 4 Accuracy – are the observations credible? –Yes, but only for sure in the most recent past –We can at least attempt to estimate errors in reconstruction datasets 4 Attribution – which part is natural variation and which part is due to anthroprogenic sources? –Some is most certainly caused by anthropogenic sources – but by how much –How much does natural variation play a role (do we understand this fully? 4 Adaptation – whatever the cause, we will need to adapt or mitigate… –Knowing that the Earth is warming is enough knowledge to require action in susceptible parts of the globe (coasts, drought-susceptible regions, etc.)