1. Current Climate Change Ch. 17, Bush

2. Outline  Evidence for recent climate change  Are humans the cause?  Potential ecological effects of climate change

3. Outline  Evidence for recent climate change  Are humans the cause?  Potential effects of climate change

4. Evidence of Temperature Changes  Three main sources of data: –Direct measurements of temperature –Location of ice caps and tropical glaciers –Thickness of ice caps

5. Temperature records  We have accurate records only for the past 120 years  Most temperature readings taken at cities which are “heat islands”

6. Whaling and Polar Ice caps

7. Changes in extent of sea ice

8. Thickness of Ice Caps  Submarines make careful measurements of the distance between the ice and the bottom of the sea  Have estimated that the thickness of the ice caps have decreased from 3.1m to 1.8m

9. Tropical Glaciers are melting  All tropical glaciers are above 4800 m  At the current rate of temperature change, it is estimated that all will be gone in 50 years Kilimanjaro

10. The effect of melting ice caps  There is not enough water trapped in the ice caps to create “Waterworld”  The biggest effect of ice caps melting comes from the decrease in ALBEDO

11. Albedo = brightness

12. Ice caps have high albedo

13. Outline  Evidence for recent climate change  Are humans the cause?  Potential effects of climate change

14. Last glacial period ended 11,000 years ago  90% of last 2 million years has been glacial  For the last 10,000 years, plants and animals have been living in an unusually warm environment

15. Temperature changes over the years  The rate of climate change we are currently experiencing is only matched by the rapid warming at the end of the last ice age

16. Temperature changes in history  Between 1400-1700 the earth was a few degrees colder  Called “The Little Ice Age”  Influenced history: –Outcome of battles –Crops failing causing famine

17. Greenhouse effect  Light energy enters the atmosphere  Changes to heat energy  Light energy exits atmosphere but heat energy is trapped

18. The Greenhouse effect  The greenhouse effect is not all bad  Without the greenhouse effect, the earth would be, on average, -18  C

19. Creation of greenhouse gases  The burning of fossil fuels is increasing the greenhouse effect  Important greenhouse gases: –HCF’s, CFC’s –Methane –CO 2 –Water vapour

20. Relative contribution of greenhouse gases to predicted warming  Other chemicals are actually better at trapping heat but CO 2 contributes more to the greenhouse effect due to the fact that it is way more abundant

21. CO 2 and water vapour  CO 2 causes minor increase in temperature  Increase in temperature causes more water vapour via evaporation  Water vapour leads to further greenhouse effect and higher temperature

22. Carbon cycle  In the natural carbon cycle, respiration and decomposition increase CO 2  Photosynthesis decreases CO 2  Burning fossil fuels now contributes to CO 2 gain

23. Fossil fuels Fossil fuels are ancient organisms that did not decompose

24. The major culprits…

25. Carbon sinks  Each year humanity dumps roughly 8 billion metric tons of carbon into the atmosphere – 6.5 billion tons from fossil fuels and 1.5 billion from deforestation  But less than half that total, 3.2 billion tons, remains in the atmosphere to warm the planet  Forests, grasslands, and the waters of the oceans are acting as carbon sinks

26. Outline  Evidence for recent climate change  Are humans the cause?  Potential effects of climate change

27. Potential effects of CO 2 increase  Predicted changes in temperature  Changes to the natural world  Changes to human life

28. Recent increases in CO 2  Jagged line is caused by seasonal changes in photosynthesis; in summer N. Hemisphere plants use up more CO 2

29. Pollution can mitigate increases in temperature  Pollutants such as those from car exhaust are causing increases in cloud cover  Cloud cover increases albedo

30. Air pollution increases albedo

31. CO 2 and temperature changes  Simulations of temperature changes are becoming increasingly accurate

32. Predicted temperature change  Five principal research groups all produce climate models  Differences arise in the predictions made about social and political change  Medium estimate is that the average temperature on Earth will rise ~3.5  C

33. Increased photosynthesis

34. Planting trees to decrease temp  Deforestation causes decreases in CO 2 absorption  Planting trees will have the opposite effect ->decreases CO 2

35. C4 evolution changing atmospheres  C4 photosynthesis appears to have evolved at a time when O 2 was high and CO 2 was low and temperatures were high

36. The global distribution of C4 plants in today's world  C4 grasslands (orange) have evolved in the tropics and warm temperate regions where C3 forests (green) are excluded by seasonal drought and fire.  C3 grasses (yellow) remain dominant in cool temperate grasslands because C4 grasses are less productive at low temperatures.

37. Temperature and precipitation

38. Climate affects ecology

39. Deserts will spread

40. N. Hemi. plants will migrate north Predicted migration of beech and maple trees

41. Migration of species  Industrialization may impede the migration of many species  Temperate species (and island species) may have nowhere to migrate to  If migration can not occur then extinction will likely take place

42. Cold-adapted species

43. Implications to Conservation

44. Extinction and global warming  One study indicated that, by 2050, current warming trends could bring about extinction of 15 to 37 percent of the 1,103 species they studied  A mere 6 degrees of global warming was enough to wipe out up to 95 per cent of the species which were alive on earth at the end of the Permian period, 250 million years ago

45. Arable land will have new locations  Best conditions for farming will move towards poles  Will be at the latitude of the Canadian Shield  More irrigation needed as crop land will be drier  Expected 20% decrease in cultivatable land

46. Other reasons why global warming a threat to life on Earth?  Incidences of heat attacks, respiratory disease and stroke will increase  Disease and pests are more likely to spread  Tropical storms, tornadoes, landslides, heatwaves and droughts will both increase in number and intensity  Air quality will become poorer  coastal cities like Miami, New Orleans, Los Angeles and Bangkok will be flooded as ocean level rises due to melting glaciers  ocean levels rise, some inland drinking water sources will become contaminated by saltwater

47. Summary  The Earth is becoming increasingly warm  Recently, humans have contributed to this phenomenon  Temperature increases will have severe effects to the natural world