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Sac State GEOG 100 - Global Climate Change

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Class 14b: Global climate changeGreenhouse effectWhat is global warming?Climate researchIs global warming happening?Is global warming unusual?What’s causing global warming?Slide 8How much more warming?So what for the weather?So what for ecosystems?So what for the oceans?Slide 13So what for cities?So what for countries?Solutions to global warmingPolitics of global warmingSlide 18Slide 19Class 14b: Global climate change• Basics of global warming• Potential effects• Politics of global warmingGreenhouse effect•Natural warming effect•Keeps Earth habitable•Greenhouse gases (GHGs)–Let in short wavelengths–Trap long wavelengthsWhat is global warming?•Global = worldwide, not universal•“Global climate change” more accurate•Increase in average world temperature•Many varied regional effectsClimate research•How do we know about past climates?•Temperature records•Observations of seasons, crops•Pollen in lake sediments•Tree rings•Ice cores (trapped air)Is global warming happening?•1990s: warmest decade of millenium–7 warmest years on record•Increase of 1.4°F in 20th century•Temperate latitudes: 5° increase in 35 yearsIs global warming unusual?•Fastest rate of warming in 1,000 years•1°C away from warmest in 125,000 years•Highest CO2 in 420,000 years•Yes, it’s been this warm before•But that doesn’t mean it’s not serious!What’s causing global warming?•Sunspot cycles?–Not since 1980s•Earth’s changing orbit?–Recent changes don’t fit•End of an Ice Age?–Maybe a little•Carbon dioxide, water vapor, methane•Naturally occurring, but increase with human activity•Rising CO2 since Industrial Revolution•Product of fossil fuels•90-99% confidence (IPCC)What’s causing global warming?•2.5° - 10°F by 2100; 5.4°F at current emission rates•A 5°F drop led to the last ice age•Climate systems are nonlinear•Earth with a feverHow much more warming?•More climatic variability•More and stronger storms–Increase in extreme weather since 1970s–90% positive from global warming•More rain in some places, less in othersSo what for the weather?•Northward climate shift of 90-350 miles•Fastest species migrate at 1.2 miles/year•Need 0.9-3.4 miles/year•Penguins and polar bears?•More dead plants  more CO2 emissions•Good for mosquitoes! And diseasesSo what for ecosystems?•Thermal expansion of warmer water•Melting ice sheets, glaciers•Rise of 1.5-3 feet by 2100•Every foot up is 100 feet inland•Increased salinity in groundwaterSo what for the oceans?•Arctic Ocean ice sheet down 40% in 30 years•Could stop the Gulf Stream•Coral reefs very sensitive to temperature•Mass die-offs worldwide since 1979So what for the oceans?•More air pollution•More deadly heat waves•Mountain glaciers disappearing, too•Water supplies for millions in danger•Sea level rise: New York, London, Bangkok, Rio, etc.So what for cities?•Some positive effects in North•Greatest threats to poorest countries•Most emissions from wealthy countries•40 countries in danger of annihilationSo what for countries?•Mitigation: reduce effects–Carbon taxes–Emissions trading–Energy efficiency, alternative fuels•Adaptation: adapt to effects–Seawalls, irrigation, etc.–No matter the cause; but who pays?Solutions to global warming•Fossil-fuel producers: little to nothing–US, Australia, Saudi Arabia, etc.–US has 4% of population, 36% of CO2 emissions•Europe: has set binding targets•Developing countries: want to develop•Small island states: want to existPolitics of global warming•Kyoto Protocol (1997)–Ratified by Europe, Russia, not US–Cuts of 7% from 1990 levels–Est. 50-70% cuts needed to stabilize CO2•Est. cost: $270-450 billion for U.S.•About the same as mitigationPolitics of global


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Sac State GEOG 100 - Global Climate Change

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