Learning Unit 9: Climatic Change

1. Learning Unit 9: Climatic Change

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3. Learning Outcomes • Describe the various human activities affecting the atmosphere • Name the greenhouse gases and explain the greenhouse effect • Explain why the increasing concentrations of greenhouse gases in the atmosphere could lead to global warming • Describe the rising trend in atmospheric temperatures over the past 100 years • Explain how forecasts can be made about the impact of global warming on humankind and the environment • Discuss the possible impacts of global warming • Discuss the steps that are being taken on a global scale to address climatic change

4. Human impacts on the atmosphere Pages 240-244 in Middleton • Human activities associated with changes in the composition of the atmosphere: • Gas emissions • Modifications to the land surface – especially to vegetation cover and soil (deforestation) • Agriculture (irrigation) • Building of dams

5. Human impacts on the atmosphere • Deforestation can affect climatic conditions: • Change of land cover from trees to grass reduces leaf area index, increases the reflectivity (albedo) of the ground surface and alters root distribution • These changes affect surface water availability, which affects soil moisture and rainfall • Large-scale conversion of forests to pasture may create a warmer and drier climate • Tropical deforestation may also affect precipitation in middle and high latitudes

6. Greenhouse trace gases Pages 244-246 in Middleton • Carbon dioxide, methane and nitrous oxide are the main greenhouse gases • Greenhouse gases occur naturally in the atmosphere. However, the concentrations of some of these gases have increased dramatically due to human activities and new gases with greenhouse properties such as chlorofluorocarbons (CFCs) has been added to the atmosphere

7. Global warming Pages 247-249 in Middleton • Proxy evidence from ice-cores which show natural fluctuations in close harmony with global temperature changes over the past 150,000 years.

8. Global warming • The temperature has increased by 0,74ºC over the 100 years between 1906 and 2005. However, from 1850 to 2008, the temperature has increased by 0,8ºC and much of the warming occurred since 1975. Temperature increase was greater at the northern latitudes, land areas warmed faster than the oceans and a few parts of the world have not warmed at all. Areas that have cooled since 1979 include south-west China and parts of the southern hemisphere oceans

9. Impacts of climate change Pages 251-262 in Middleton Evidence of ecological changes

10. Impacts of climate change Rising sea levels – loss of sea ice • The rate of decline in Arctic sea ice has been faster than what was predicted • Sea ice has a high albedo, which reflects sunlight back into space • Reflection of sunlight has cooling effect • Expanding, darker areas of open water absorb sunlight and increases temperatures • Feedback contributes to the rapid loss of sea ice • Sea-level rise takes place due to thermal expansion of the oceans and input from melting sea ice • Sea-level rise in the 20th century was about 1,5-2,0 mm/year and this has accelerated in the 21st century • If the Greenland and Antarctic ice sheets melt completely, the sea level may rise with about 70m

11. Impacts of climate change Rising sea levels – loss of sea ice • Effects of sea level rise on people: • Increased flooding and inundation of low-lying settlements on coastal areas – including big cities (Bangkok, Kolkata, Lagos, London, New York, Rio de Janeiro, Shanghai and Tokyo) • Venice, Italy is particularly at risk, because most of the urban area is only 90cm above the mean sea level • Densely populated river deltas are among the most vulnerable flood-prone regions • Several small island developing states (SIDS) may lose significant proportions of their national territory

12. Impacts of climate change Small island developing states (SIDS) • Several small island developing states (SIDS) may lose significant proportions of their national territory such as: Tuvalu, Tonga, Kiribati, Marshall Islands and the Maldives • Larger islands, such as Fiji and Samoa could also face difficulties since most settlements and infrastructure are in the coastal zone, while inland regions may experience ecological changes. • Sea level rise may change coastal erosion rates • Meteorological (weather) hazards, such as tropical cyclones, may be exacerbated

13. Impacts of climate change Extreme weather events of the 21st century

14. Impacts of climate change

15. Responses to global climate change “No-regrets” initiatives under the Kyoto Protocol

16. Responses to global climate change Adaptive measures in the Maldives