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Global Climate Change

Global Climate Change

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Global Climate Change

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  1. Global Climate Change

  2. Our changing climate

  3. What is Climate Change? • Climate = long-term weather patterns (what you expect; weather is what you get!) • GCC = changes in long-term pattern of atmospheric conditions involving ∆T, precipitation, storm frequency & intensity • Global warming is one aspect

  4. Greenhouse Effect • Short-wave radiation absorbed by earth • Earth warms up, releases IR radiation • Tropospheric greenhouse gases (CO2, CH4, H20) absorb IR

  5. Greenhouse Effect • Due to abundance, CO2 is of primary concern • Current levels at their highest in 650,000 – 2,000,000 years • Fossil fuel burning, forest clearing and burning are the two main anthropogenic sources of increased CO2 levels

  6. Greenhouse Gases • Methane (from fossil fuel extraction, cattle, landfills, certain crops like rice) • N2O from feedlots, automobiles, agriculture • Tropospheric O3 • Halocarbons have decreased due to Montreal Protocol of 1987 • Aerosols may have short-term cooling effect

  7. Other Factors • Milankovitch cycles = changes in the earth’s rotation and orbit around the sun • Solar output and solar cycle • Ocean absorption of CO2

  8. Other Factors El Niño = • Equatorial winds weaken and allow warm water from western Pacific to move eastward • Prevents cold water from upwelling in eastern Pacific La Niña = • Cold surface waters extend far westward

  9. Other Factors • Thermohaline circulation = worldwide current system in which warmer fresher water moves along the surface; colder, saltier water moves down • North Atlantic Deep Water = warm surface water moves northward toward Europe; cooler water sinks and returns in other direction

  10. Studying climate change

  11. Proxy Indicators • Preserved gas bubbles in ice • Sediment beds beneath bodies of water • Coral reefs and tree rings • All are forms of indirect evidence

  12. Atmospheric Sampling • Started in 1958 – Charles Keeling of Scripps Institution of Oceanography – trends of CO2 concentrations • His data showed shows an increase of CO2 concentrations from 315 to 383 ppm

  13. Modeling • Coupled general circulation models (CGCMs) • Combine what is known about weather patterns, atmospheric circulation, atmosphere-ocean interactions, and feedback mechanisms to simulate climate processes • Over a dozen research labs world wide • A good approximation of relative effects of natural and anthropogenic influences

  14. Current & future impacts

  15. IPCC Report 2007 – summarized 1000s of reports Includes trends in sfc temp, rainfall patterns, snow & ice cover, sea levels, storm intensity, etc Included a series of possible climate change scenarios, including: • Temp increases (1.33oF in last century) • Increases in power and duration of storms • Changes in precipitation

  16. Muir Glacier: 1948 and Now

  17. IPCC Report • Polar ice melt • Glaciers disappearing (Since 1980 – glaciers have lost an average of 9.6 m vertical • This changes earth’s albedo • Rising sea levels (3.1 mm/y from 1993 – 2003) • A several inch vertical rise = many feet of horizontal incursion into coastal lands

  18. IPCC Report • Storm surges present a great risk to island nations • Rising sea levels will force people to choose between relocating or investing in costly protections • Ecosystems also affected • Timing of seasonal events are creating complex effects in ecosystems

  19. IPCC Report Societal impacts will also occur • Agriculture – cuts in productivity (drought & flood) • Forestry – insects, disease outbreaks, , invasive species, fires • Health – heat stress, tropical diseases, respiratory ailments, hunger • Economics – est. of 1 – 5% of GDP

  20. Responding to climate change

  21. Our Response Mitigation or adaptation? • Mitigation = actions that would reduce emissions of GHG • Adaptation = search for ways to soften the blow (building sea walls is an ex.) • Electricity generation is largest source of GHG in US • Conservation & efficiency

  22. Our Response • Natural gas has less impact • Carbon sequestration would allow current practices to continue • Transportation is 2nd largest source • Cars are highly inefficient (15%) • Alternative engines, driving less, public transportation are possibilities

  23. Our Response • Sustainable agriculture & land management • Reduce methane emissions from rice fields, cattle • Preserving forests; increase reforestation • Recovering methane from landfills, treating wastewater, energy from solid waste

  24. Our Response Kyoto Protocol • Began as the UN Framework Convention on Climate Change • Binding international treaty to reduce GHG emissions (US refused to sign) • In the 10 years after Rio conference (1992) – US increased GHG by 13%; Germany & UK decreased by 13 – 18%

  25. Our Response • Market mechanics – cap and trade • A carbon offset represents a reduction in emissions somewhere else - like a renewable energy or a reforestation project - to balance out the emissions you cannot reduce. • Reduce your own carbon footprint

  26. Ozone depletion

  27. UVA: λ = 320-400nm • Causes tanning • UVB: 290-320nm; burns, skin cancer • UVC: 10-290nm formation of ozone

  28. Research CFCs are persistent in the atmosphere • Rise into the stratosphere over 11-20 years • Break down under high-energy UV radiation • Halogens produced accelerate the breakdown of O3 to O2 • Each CFC molecule can last 65-385 years

  29. Reducing Effects • Stop producing all ozone-depleting chemicals • 60–100 years of recovery of the O3 layer • 1987: Montreal Protocol; 1992: Copenhagen Protocol • Ozone protocols: prevention is the key • Substitutes for CFCs are available

  30. Conclusion • Many factors, including human activities, can shape atmospheric composition and global climate. • Scientists and policymakers are beginning to understand anthropogenic climate change and its environmental impacts more fully. • Reducing greenhouse gas emissions and taking other actions to mitigate and adapt to climate change represents the foremost challenge for our society in the coming years.