1. Evidence of Climate Change page 18 We all have heard the term ‘global warming’ but is there any evidence that our climate is changing?

2. 1. Melting Ice Many glaciers that have been getting smaller recently 1890 1990

3. parts of Antarctic ice sheet are breaking up 1988 2008

4. 2. Rising Sea Levels Higher sea levels means more flooding

5. The total number of storms has not varied over time BUT The number of short-duration SEVERE storms has increased 3. Storm Intensity

6. 4. Coral reef size Coral reefs have been shrinking in most places. Area covered by coral reefs in four parts of the Caribbean as measured over time.

9. What evidence is there that climate has been changing over longer periods? All of these changes have been recent, 100 years or so!

10. 5. Fossil records Fossil of a tree from Antarctica, an area far too cold for modern forests

11. 6. Tree Rings (or dendrochronology) relative growth of trees each year gives clues to climate conditions in the past

12. How far back does this record go? 1000 years?quite a few trees this old 5000 years?a few trees this old 10000 years?no trees this old but can use old dead trees to go back this far

13. The problem with tree rings is they only give us clues as to how well the tree grew at that time. They give us no other information about the other conditions at that time. Researchers want to see into the past and find more than just temperature data. Where can they look? What should they look for?

14. 7. Ice Core Data drill down into glaciers or ice sheets

15. Like trees, ice cores have ‘rings’ analysis of these ‘rings’ allows researchers to determine there is gas trapped in the ice  past atmosphere gases melt & freeze patterns and O 2 isotopes  past temperatures

16. [Antarctica] Results? temperature has varied over the past 400,000 years It has been up to 4 o C warmer and 8 o C cooler than now

17. CO 2 levels have also varied over the past 400,000 years The question is, are the variations related?

18. When CO 2 is low, temp is lowWhen CO 2 is high, temp is high

19. Have any other gases varied over time? Yes! Nitrous oxide (N 2 O) has increased a lot since 1800’s

20. methane (CH 4 ) has increased a lot since 1800’s

21. sulphate (SO 4 ) ions have increased a lot since 1800’s

22. Note that all four gases show similar patterns and all correlate to increases in temperature

23. Are all of these changes that we have seen related? ice melting,rising sea levels,more intense storms shrinking coral reefs All result from warmer temperatures CO 2, N 2 O, CH 4 and SO 4 gases are all natural greenhouse gases involved in Earth temperature Therefore the question now is what is causing all of these changes?