BESC 201 11 18 2013 Lecture 32 Outline of Last Lecture I Indoor Air Pollution Outline of Current Lecture II Chapter 14 Central Case Study III Our Dynamic Climate IV Studying Climate Change V Current and Future Trends and Impacts Current Lecture 11 18 2013 Global Climate Change Central Case Study Rising Seas May Flood the Maldives The world s oceans rose 10 20 cm during the 20th century as warming temperatures expanded ocean water and as melting polar ice discharged water into the ocean Higher seas would flood large areas of the Maldives and cause salt water to contaminate drinking water supplies Storms intensified by warmer water temperatures are expected to erode beaches and damage the coral reefs The underwater cabinet meeting kicked off a global campaign to draw attention to the impacts of climate change Our Dynamic Climate What is climate change Climate an area s long term atmospheric conditions including temperature precipitation wind humidity barometric pressure solar radiation and other characteristics Global Climate Change modifications in aspects of Earth s climate Global Warming specifically to an increase in Earth s average surface temperature Three factors influence climate 1 The sun 2 The atmosphere 3 The oceans These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute Greenhouse gases warm the lower atmosphere Greenhouse Gases atmospheric gases with three or more atoms in their molecules tend to absorb infrared radiation very effectively A diverse group of mostly human made gases that includes chlorofluorocarbons Greenhouse Effect some reemitted energy travels back downward instead of being lost to space warming the atmosphere and the planet s surface Global warming potential refers to the relative ability of one molecule of a given greenhouse gas to contribute to warming Other factors warm or cool the surface Aerosols microscopic droplets and particles Radiative Forcing the amount of change in thermal energy that a given factor causes Climate caries naturally for several reasons Milankovitch Cycles over thousands of years our planet wobbles on its axis varies in the tilt of its axis and experiences changes in the shape of its orbit all in regular long term cycles of different lengths Alter the way solar radiation is distributed over Earth s surface Solar Output The variation in solar energy reaching our planet in recent centuries has not been great enough to drive significant temperature changes in Earth s surface Ocean Absorption The oceans hold 50 times more carbon than the atmosphere does Ocean Circulation Ocean water exchanges heat with the atmosphere and ocean currents move energy from place to place Studying Climate Change Proxy indicators tell us about the past Proxy Indicators types of indirect evidence that serve as proxies or substitutes for direct measurement and that shed light on past climate Models help us predict the future Climate Models programs that combine what is known about atmospheric circulation ocean circulation atmosphere ocean interactions and feedback cycles to stimulate climate processes Current and Future Trends and Impacts The IPCC summarizes evidence and predicts impacts Intergovernmental Panel on Climate Change IPCC consists of many hundreds of scientists and governmental representatives that reviews and summarizes immense amount if scientific information on climate change in periodic reports Fourth Assessment Report summarized many thousands of scientific studies and it documented observed trends in surface temperature precipitation patterns snow and ice cover sea levels storm intensity and other factors and also predicted future changes in these phenomena after considering a range of potential scenarios for future greenhouse gas emissions Temperatures continue to rise Average surface temperatures on Earth rose by an estimated 0 74 C in the century from 1906 to 2005 Precipitation is changing too A warmer atmosphere holds more water vapor but changes in precipitation patterns have been complex with some regions of the world receiving more rain and snow than usual and others receiving less Melting ice and snow have far reaching effects Mountaintop glaciers are disappearing As warming temperatures diminish mountain glaciers this will reduce summertime water supplies to millions of people Snow cover ice sheets and sea ice will continue to diminish near the poles Rising sea levels may affect hundreds of millions of people Storm Surge a temporary and localized rise in sea level brought on by the high tides and winds associated with storms If sea levels rise as predicted hundreds of millions of people will be displaced or will need to invest in costly efforts to protect against high tides and storm surges Climate change threatens coral reefs Ocean Acidification as ocean water absorbs atmospheric CO 2 it becomes more acidic and this impairs the ability of coral and other organisms to build exoskeletons of calcium carbonate Climate change affects organisms and ecosystems Biologists are recording spatial shifts in the ranges of organisms as plants and animals move toward the poles or upward in elevation If climate change decreases plant growth through drought fire or disease then carbon flux to the atmosphere could increase