Climate Change

1. Climate Change • Stratosphere made up of gases that trap radiation (heat) from earth’s surface, causing it to be warmer than otherwise • Acts like greenhouse, sunlight let in but not all radiation let out • Natural effect that is vital to human life

2. Increasing greenhouse gases are related to an estimated warming of the earth of 0.3 degrees (celsius) per decade. • This is much greater than estimate rate of change during previous periods of warming and cooling (0.05 degrees celsius)

3. Effects (Damage) of Climate Change • Sea levels expected to rise due to melting ice in polar regions • Coastal regions forced to adapt • Changes in agriculture; rising temperature may change location of crops • Many poor countries largely dependent on agriculture • Effects expected to be negative but actual changes are unknown • Changes in ocean current

4. Scientists link increase in greenhouse gases to human activity • Many human activities (such as exhaling) involve emission of greenhouse gases • Increase in greenhouse gases linked to economic activity involving burning of fossil fuels

5. Carbon Dioxide is the most important greenhouse gas in stratosphere • CO2 in the atmosphere has grown by 20% over the last 250 years • In the last 30 years alone it has grown 8%

6. Urbanization and Greenhouse Gases A large part of the human contribution to CO2 emissions: A. Household consumption B. Household transportation Activities involving consumption of energy (fossil fuels)

7. Household Consumption • Weather conditions responsible for substantial part of variation in household energy use A. Heating in winter B. Cooling in summer Household Transportation • Differences across urban areas in commuting distance is a large determinant of variation in household transportation

8. The Greenness of Cities: Carbon Dioxide Emissions and Urban Developmentby Glaeser and Kahn - examines how the location and form of US cities affect CO2 emissions

9. Relationship between transportation and CO2 comes mainly in form of burning gasoline • Using National Household Transportation Survey data, study finds gasoline consumption is: • positively related to household income and size • positively related to the household’s distance from the CBD • inversely related to the population density of the census tract the household is located in • inversely related to the density of the metropolitan area

10. Household Gasoline Consumption in Urban Areas Uses the average family with 2.62 members and income of $62,500 Predicts gasoline usage for the family in each urban area • Prediction derived from placing average family in each census tract in urban area and simulating gasoline use • Variation in predictions comes from differences in form of urban area Graph

11. Households and CO2 Emissions • Household use of natural gas, electricity estimated by urban area • Home heating, electricity influenced by climate • Relationships generated by placing the average household in the various urban areas Graph

12. Ranking Urban Areas • Western urban areas more likely to consume electricity from nuclear, hydro, wind • Conversion of household energy use to CO2 takes source and region into account • Gasoline consumption converted to 23.46 lb of CO2 per gallon consumed Table ranking urban areas