Geography 5 Week 8 Lecture 13 05 22 12 The Science and Politics of Global Warming Earth Sun Relations Recent solar output variation too small to account for current climate changes o But has increased 25 over the last 4 billion years Milankovitch cycles o Variations in the Earth s orbit p lay a role in determining medium term climatic patterns o Axial tilt Changes from 22 1 to 24 5 on a 41 000 year cycle o Axial precession 26 000 year cycle Gyroscopic motion o Earth s Albedo Atmospheric interference Clouds dust can reflect solar radiation and lead to cooling Earth s surface Ice and high albedo surfaces reflect solar radiations The Green House Effect Radiation wavelengths o Hotter objects emit shorter wavelengths o Solar shorter v terrestrial radiation longwave The atmosphere and Green House Gasses GHGs o Water Vapor Carbon Dioxide CO2 Methane CH4 Nitrous Oxide N20 Ozone 03 o GHGs let in short wave radiation trap long wave radiation o GHGs contribute to the greenhouse effect Water vapor 36 72 CO2 9 26 Methane 4 9 very potent Ozone 3 7 o Where does it come from Break up of Pangaea Biological process in low oxygen environments swamps Release methane Burning fossil fuels natural fires Animal husbandry agriculture Field and forest clearing burning Carbon dioxide sinks Plants via photosynthesis The ocean Report by the intergovernmental panel on climate change 2007 Global scientific community consensus Rising temperatures o 95 06 among the warmest in the instrumental record since 1850 industrial revolution o Most drastic temperature changes will be in arctic because of the ice melting lowers the albedo Arctic melting faster than the Antarctic because the arctic is on top of water Cause of Recent Climate Change IPCC 2007 Most of the observed increase in global average temperatures since the mid 20th century is very likely due to the observed increase in the anthropogenic GHG concentration very likely 95 Observed increase in CO2 Concentrations Increases in release of Carbon Emission from Fossil Fuel burning Some Measureable Impacts IPCC 2007 Rises in global average sea level IPCC 2007 o 1 8 mm yr 1961 93 o 3 1mm yr 93 present decrease in ice Positive feed back systems may accelerate Climate Change Ex Ice Cap Melting o Higher temp melting ice reduced albedo greater absorption of energy higher temperature o E g melting permafrost Decay of peat moss releases methane IPCC Report Flaws E g claimed Himalayan Glaciers will disappear by 2035 o Since withdrawn admitted not adequately peerreviewed Impacts of Global Warming on CA Sea level rises flooding of coastal areas with populations o One meter rise in the bay area region o 33 and 55 inch rises in seal beach Huntington beach area o Saltwater intrusion into coastal aquifers o Reduced snowpack earlier snowmelt o Increased evapotranspiration Reduced reservoirs Increase water necessary for agriculture landscaping o Shifting of vegetative communities o Greater likely hood of prolonged droughts o Wildfire increase o Higher stream and reservoir temperatures and habitat change Increased demand for energy air conditioning