2 We all have heard the term ‘global warming’ but is there any evidence that our climate is changing?
3 1. Melting Ice18901990Many glaciers that have been getting smaller recently
4 parts of Antarctic ice sheet are breaking up 19882008
5 2. Rising sea LevelsHigher sea levels means more flooding
6 3. Storm IntensityThe total number of storms has not varied over time BUTThe number of short-duration SEVERE storms has increased
7 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.
8 All of these changes have been recent, 100 years or so! What evidence is there that climate has been changing over longer periods?
9 5. Fossil recordsFossil of a tree from Antarctica, an area far too cold for modern forests
10 6. Tree Rings (or dendrochronology) relative growth of trees each year gives clues to climate conditions in the past
11 How far back does this record go? 1000 years?quite a few trees this old5000 years?a few trees this old10000 years?no trees this oldbut can use old dead trees to go back this far
12 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?
13 7. Ice Core Datadrill down into glaciers or ice sheets
14 Like trees, ice cores have ‘rings’ analysis of these ‘rings’ allows researchers to determinemelt & freeze patterns and O2 isotopes past temperaturesthere is gas trapped in the ice past atmosphere gases
15 temperature has varied over the past 400,000 years [Antarctica]Results?temperature has varied over the past 400,000 yearsIt has been up to 4oC warmer and 8oC cooler than now
16 CO2 levels have also varied over the past 400,000 years The question is, are the variations related?
17 When CO2 is low, temp is low When CO2 is high, temp is high
18 Have any other gases varied over time? Yes!Nitrous oxide (NO) has increased a lot since 1800’s
20 sulphate (SO4) ions have increased a lot since 1800’s
21 Note that all four gases show similar patterns and all correlate to increases in temperature
22 Are all of these changes that we have seen related? ice melting,rising sea levels,more intense stormsshrinking coral reefsAll result from warmer temperaturesCO2, N2O, CH4 and SO4 gases are all natural greenhouse gases involved in Earth temperatureTherefore the question now is what is causing all of these changes?