Energy, Power and Climate Change The Greenhouse Effect Global Warming

The Greenhouse Effect: Physical Processes Short wavelength radiation from the sun heats the surface of the Earth Earth emits infrared radiation (longer wavelengths) Some of the the infrared radiation is absorbed by the gases in the atmosphere This is called The Greenhouse Effect

The Greenhouse Effect: Physical Processes Gases that absorb infrared radiation are called Greenhouse gases Upper atmosphere and Earth’s surface are warmed Temperature of the Earth’s surface will be constant if the rate at which the Earth absorbs energy equals the rate at which it radiated energy

Greenhouse Effect Greenhouse Effect is a natural process Without it, the Earth’s temperature would be much lower Average temperature of the moon’s surface is more than 30°C colder than the Earth

Greenhouse Effect

Greenhouse Gases Greenhouse gases are naturally occurring Balance in the atmosphere can be altered due to industry and technology

Main Greenhouse Gases Methane CH 4  Principal component of natural gas  Product of decay, decomposition or fermentation  Also produced by livestock and plants Water H 2 O  Water vapor in upper atmosphere (not the same as clouds, clouds are condensed water vapor)  Don’t alter greatly due to industry

Main Greenhouse Gases Carbon Dioxide CO 2  Released during combustion  Significantly increases greenhouse effect  Removed by plants from the atmosphere during photosynthesis (carbon fixation) Nitrous Oxide NO 2  Main sources are livestock and industry (e.g. the production of nylon)  Significant effect - can remain in the upper atmosphere for long periods of time

Other Greenhouse Gases Ozone O 3  Ozone layer absorbs harmful high energy UV photons  Adds to the greenhouse effect Chloroflourocarbons (CFCs)  Used as refrigerants, propellants, cleaning solvents  Deplete the ozone layer

Resonance and Greenhouse Gases Greenhouse gases absorb infrared radiation due to resonance Natural frequency of oscillating bonds within gas molecules is in the infrared region Amplitude of vibration increases, so temperature increases Absorption takes place at specific frequencies

Absorption Spectra of Greenhouse Gases

Global Warming

Causes of Global Warming Changes in the composition of greenhouse gases  Can be natural effects  Can be caused by human activities (enhanced greenhouse effect) Changes in the intensity of radiation emitted by the sun, for example, increased solar flare activity Cyclical changes in the Earth’s orbit and volcanic activity

Causes of Global Warming Generally accepted view is that the increased combustion of fossil fuels has released extra carbon dioxide into the atmosphere, enhancing the greenhouse effect

Evidence for Global Warming Ice core data - Antarctica Each year’s new snow fall adds another layer of ice Variations of temperature measured, and concentration of greenhouse gases trapped in air bubbles in ice also measured - variations of carbon dioxide and temperature correlate closely

Evidence for Global Warming

Mechanisms of Global Warming Reduces ice/snow cover, reducing albedo - increases rate of heat absorption Temperature increase reduces solubility of CO 2 in the sea, increasing CO 2 in the atmosphere Increases rate of evaporation and the ability of the atmosphere to hold water vapor

Mechanism of Global Warming (continued) Significant release of trapped CO 2 in tundra (frozen subsoil) areas Deforestation increases CO 2 in the atmosphere, and reduces carbon fixation

What is positive feedback? Mechanisms increase the rate of global warming when small temperature increases result in further temperature increases Some have suggested that negative feedback may occur and temperatures may fall in the future

Effects of Global Warming Most models suggest global warming will cause climate changes that will result in a rise is sea level Water decreases in volume when ice melts from 0°C to 4°C, so melting ice floating on sea water will decrease sea level (Arctic ice at the North Pole) BUT the ice melting on land will cause increases in sea level (glaciers, snow on mountains, Antarctic ice at South Pole)

Coefficient of Volume Expansion Records fractional change in volume per degree change in temperature

Global Warming Predictions Temperature will rise between 1.8 and 4°C or more by the end of the century Sea levels will rise between 18 and 59 cm by the end of the century, with 10 to 20 cm more possible due to melting  much of the world’s population is concentrated in coastal cities  a 10 cm increase would flood much of Southeast Asia

Global Warming Predictions (continued) Hot extremes, heat waves, heavy rains will become more frequent Hurricanes, droughts, wildfires will become commonplace Growth of deserts will cause food shortages Glaciers would melt, increasing sea level, and causing water shortages for those dependent on runoff for fresh water

Global Warming Predictions (continued) More than a million species face extinction due to disappearing habitats, changing ecosystems and acidifying oceans

Possible Solutions to Reduce Greenhouse Effect Reduction in use of fossil fuels Advances in technology  Improve efficiency  Decarbonizing exhaust gases from power plants (remove and store CO 2 )  Fusion reactors made operational Replacing use of coal and oil  Renewable energy sources and/or nuclear power to eliminate emissions

Possible Solutions to Reduce Greenhouse Effect Reduction of energy requirements  Improving thermal insulation in dwellings  Reducing journeys and using more energy efficient transport (hybrid cars)  Use of combined heating and power systems Planting new trees and maintaining existing forests

International Efforts Intergovernmental Panel on Climate Change (IPCC) - The World Meteorological Organization (WMO) and the United Nations Environment Program (UNEP) established the IPCC in 1988 Governmental scientific representatives worldwide assess international research on global warming and human induced climate change

International Efforts Kyoto Protocol - Amendment to the UN Framework Convention on Climate Change Countries agree to reduce greenhouse gas emissions Some countries haven’t signed (US, Australia) and others aren’t required to reduce emissions (China, India)

International Efforts Asia-Pacific Partnership on Clean Development and Climate (APPCDC) Six countries use 50% of world’s energy have agreed to work together to meet goals for energy security, reduction of air pollution, and climate change Australia, China, India, Japan, Korea, US