Transcript Document
Carbon & Climate Atmospheric Carbon Dioxide CO2 was measured in the atmosphere starting in the 1950’s at Mauna Loa, Hawaii CO2 concentrations have increased:315 ppm to 380 ppm Greenhouse gases and temperature Air trapped in ice cores give a record of past atmosphere CO2 was stable for past 1000 years at 280 ppm Current temperature increase a sharp change from past 1000 years The Current Atmosphere…. • Clear correlation between atmospheric CO2 and temperature over last 160,000 years • Current level of CO2 is outside bounds of natural variability •Rate of change of CO2 is also unprecedented Source: OSTP Greenhouse gases Some solar radiation is reflected by atmosphere and Earth Sun Atmosphere Earth More radiation is absorbed by Earth and warms it Infrared radiation (heat) is released from the Earth Some infrared radiation is absorbed by greenhouse gases warming Earth and lower atmosphere Greenhouse gases Greenhouse warming potential (GWP) -- takes into account the ability of a gas to absorb infrared radiation, and the lifetime of the gas in the atmosphere Gas carbon dioxide (CO2) methane (CH4) [conc] 360 ppm 1745 ppb GWP 1 23 nitrous oxide (N2O) CFC-11 314 ppb 268 ppt 296 4600 CFC-13 4 ppt 14000 Greenhouse gases Note about CFC’s: These gases affect the ozone layer in the stratosphere BUT, that is not related to their effect as a greenhouse gas in the troposphere Greenhouse gases Carbon dioxide is the largest single contributer to climate forcing Carbon dioxide contributes about half of total climate forcing from greenhouse gases Other important greenhouse gases include methane, nitrous oxide, CFCs whrc.org/carbon/ Carbon dioxide balance Atmospheric increase = Fossil fuel + Land Clearing - Ocean Dissolution Land Uptake Atmospheric Increase Fossil Fuel Land Clearing Ocean Atmosphere Flux Land Uptake 3.3 +5.4 +1.7 -1.9 -1.9 Pg? whrc.org/carbon/ Where’s the Carbon? Missing sink is large, unmeasured & thought to be uptake by terrestrial biomes 1. CO2 fertilization of temperate, tropical and boreal forests? 2. Regrowth of previously deforested areas? 3. Extension of growing season (warmer temp)? 4. Nitrogen fertilization of natural ecosystems? The Future Atmosphere…. Assuming ‘business-asusual’…. Atmosphere CO2 will be double that of preindustrial concentrations by 2050 By 2100 the atmosphere will be between 600 - 800 ppm Climate predictions General circulation models (GCM) are used to predict future climate Driven by physical processes that involve transfers of energy and water Used with different greenhouse gas ‘scenarios’ to predict climate in a future atmosphere Climate warming predicted 1.5 - 6 deg C High latitudes & and land surfaces warm most Washington DC now has 30 days over 90 deg F. Will have 85 days over 90F Changes in Arid zones may Wet tropics may precipitation are more become drier become wetter variable globally Model Prediction Depend on Future Scenarios Potential Climate Change Impacts Health Weather-related mortality Infectious diseases Air-quality respiratory illnesses Agriculture Climate Changes Temperature Precipitation Sea Level Rise Crop yields Irrigation demands Forests Change in forest composition Shift geographic range of forests Forest health and productivity Water Resources Changes in water supply Water quality Increased competition for water Coastal Areas Erosion of beaches Inundation of coastal lands Costs to protect coastal communities Species and Natural Areas Source: EPA Shift in ecological zones Loss of habitat and species Effects of Climate Change Effects of Climate Change Sea level rise due to ice cap melting on land Also due to thermal expansion of water. Water is less dense when warmer Effects of Climate Change Sea level change in FL Effects of Climate Change Low island nations (Tonga, Marshall islands) are a few meters above sea level Inhabitants of these islands may become the first ecorefugees as sea level rises Effects of Climate Change Forest edge will move north and be replaced by savanna and woodland Forest around Gainesville will become less dense with trees and grasses South Florida will become more dense tropical forest Effects of Climate Change Initially, an increase in crop production in US due to CO2 fertilization Canada and other northern countries become warmer with higher crop yield US, South America, Africa become warmer, drier with lower crop yield Stabilizing The Future Atmosphere Can we change our trajectory? Stable atmospheric CO2 depends on changing emission rate For all scenarios, final emission rates must equal natural uptake (very low) Stabilizing The Future Atmosphere Do we have the political will? Industrial countries must decrease emission rates by 5-8 % by 2012 (US not a participant) After 2012, no agreement, but other (developing) countries will have to decrease emissions How to Reduce Emission Rates? The hydrogen economy Managing forests as C sinks Engineering solutions: deep sea bedrock