Global Warm

1. Unit 6: TheIssue of Global Warming 6.1 Causes “Sadly, it’smucheasiertocreate a desertthan a forest.”

2. Global Warming Global warming is the increase in the average temperature of Earth's near-surface air and oceans since the mid-20th century and its projected continuation. According to the 2007 Fourth Assessment Report by the Intergovernmental Panel on Climate Change (IPCC), global surface temperature increased 0.74 ± 0.18 °C (1.33 ± 0.32 °F) during the 20th century.

3. Global Warming Most of the observed temperature increase since the middle of the 20th century was caused by increasing concentrations of greenhouse gases, which results from human activity such as fossil fuel burning and deforestation.

4. Global dimming Global dimming, a result of increasing concentrations of atmospheric aerosols that block sunlight from reaching the surface, has partially countered the effects of greenhouse gas induced warming. Global dimming, a gradual reduction in the amount of global direct irradiance at the Earth's surface, has partially counteracted global warming from 1960 to the present.

5. Global dimming The main cause of this dimming is aerosols produced by volcanoes and pollutants. These aerosols exert a cooling effect by increasing the reflection of incoming sunlight. The effects of the products of fossil fuel combustion—CO2 and aerosols—have largely offset one another in recent decades, so that net warming has been due to the increase in non-CO2 greenhouse gases such as methane.

6. Global dimming Radioactive forcing due to aerosols is temporally limited due to wet deposition which causes aerosols to have an atmospheric lifetime of one week. Carbon dioxide has a lifetime of a century or more, and as such, changes in aerosol concentrations will only delay climate changes due to carbon dioxide.

8. Thecontroversy The only environmental issue to have caused as much debate and discussion as climate change was probably human population growth. But this is clearer to deal with since we can directly identify the effects of overpopulation.

9. Thecontroversy Climate change and global warming have become very important issues involving national and international politics, global economics and the fate of national econimics all bound up with scientific debate about the evidence and the cause and effect.

10. Facts There is a greenhouse effects. The greenhouse gas emissions are increasing due to human activities, which are increasing the greenhouse effect. There has been a arecent pattern of increased average global temperature.

11. But… There is not total agreement over the cause of the rise in temperature nor over what we should be doing about it. A small number of scientists question the cause and effect of the global warming, some citing the Earth’s ratational wobble, sunspot activity or that increased temperature is causing increased greehouse gases, not the other way around.

12. Whatshouldbe done??? Possible actions may be preventive (e.g. reduce burning of fossil fuels). Or lessen the impact of climate change (e.g. build flood barriers). Or we may take no action.

13. The IPCC The IPCC is the Intergovernmental Panel on Climate Change, it was set up by the UN Environment Programme and the World Metereological Organization in 1988 to look into this issue. The ICPP state that “the globally averaged net effect of human activities since 1750 has been one of warming.”

14. Thegreenhouseeffect The GHE is a good thing for life on Earth. Without it there would be no life as we know it. Without GHE the Earth’s average surface temperature would be 33°C colder than it is now. The effect is caused by gases in the atmosphere reducing heat losses by radiation back into space.

15. Thegreenhouseeffect These gases work be reducing convection currents in the air inside the greenhouse which is warmer than air outside. Greenhouse gasses absorb infrared radiation reradiated from the Earth’s surface and pass this as heat to the other atmospheric gasses.

19. Enhancedgreenhouseeffect As humans increase the emissions of some of the greenhouse gases, the greenhouse effcet is exagerated or enhanced. Most climatic scientist believe that this is causing global warming and climate change.

20. This figure shows the predicted distribution of temperature change due to global warming

21. Majorgreenhouse gases Carbon dioxide Water vapor Methane CFC’s HCFC’s Nitrous oxide Ozone

22. HW: Answer What is the effect or function of water vapor in relation to the greenhouse effect? What is the effect or function of CFC’s in relation to the greenhouse effect? What is radioactive forcing? How is the concentration of methane increased in the atmosphere? Name at least two sources.

23. Complete thetable: