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EDU 711 Science and Technology Education Trimester 1 2014 Week 13 Lecturer : Mrs. Runaaz Sharma Global Warming Greenhouse Gases and Climate Is the climate becoming warmer and warmer? • According to the National Academy of Sciences, the Earth's surface temperature has risen by about 1 degree Fahrenheit in the past century, with accelerated warming during the past two decades. There is new and stronger evidence that most of the warming over the last 50 years is attributable to human activities. Human activities have altered the chemical composition of the atmosphere through the buildup of greenhouse gases – primarily carbon dioxide, methane, and nitrous oxide. The heattrapping property of these gases is undisputed although uncertainties exist about exactly how earth's climate responds to them. (source: US-EPA) The real greenhouse These two aspects make the greenhouse warmer than outside air temperature Another Example of the Greenhouse Effect The Sun’s energy passes through the car’s windshield. This energy (heat) is trapped inside the car and cannot pass back through the windshield, causing the inside of the car to warm up. Greenhouse Effect Natural Greenhouse effect The natural greenhouse effect causes the mean temperature of the Earth's surface to be about 33oC warmer than it would be if natural greenhouse gases were not present. Enhanced greenhouse effect When concentrations of greenhouse gases increase, more infrared radiation is returned toward the earth and the surface temperature rises. Greenhouse Effect & Global Warming • The “greenhouse effect” & global warming are not the same thing. – Global warming refers to a rise in the temperature of the surface of the earth • An increase in the concentration of greenhouse gases leads to an increase in the magnitude of the greenhouse effect. (Called enhanced greenhouse effect) – This results in global warming What are the major greenhouse gases? • H2O • CO2 • CH4 • N2O • O3 • CFCs • SF6 What determines the contribution of a greenhouse gas to global warming? • Concentrations ▫ H2O and CO2 are the two biggest contributors to the atmospheric warming because of their higher concentrations. • Lifetime ▫ The longer-live a gas is, the higher the contribution. e.g. N2O contribution > CH4 • Effectiveness as an infrared absorber ▫ For example, CFC-11 and CFC-12 Greenhouse Gases • The primary components of Earth’s atmosphere, N2 and O2 do not have absorption in the IR wavelength range, therefore, do not have a significant role in setting the surface temperature of the planet… • Greenhouse gas are efficient in absorbing IR light… The most important greenhouse gases are: ▫ H2O – Water vapor. ▫ CO2 – Carbon Dioxide ▫ CH4 – methane The most abundant greenhouse gas in Earth’s atmosphere is water vapor. Most of the greenhouse heating of Earth’s atmosphere is due to Water vapor absorption of IR radiation emitted by Earth, and then transferring the energy to the surrounding air molecule Consequences of global warming • Sea level rise ▫ Beach erosion ▫ Coastal wetland loss ▫ Loss of low-lying territories • Water resources change ▫ Precipitation pattern shift ▫ Increases instances of heavy precipitation ▫ New burdens on water capture, storage and distribution system to be expected. • Effects on agriculture ▫ Changes in the length of growing season ▫ Growth of undesirable plant species Consequences of global warming… • Effects on air quality ▫ Increase in reaction rates and concentrations of certain atmospheric species increase in O3 in urban areas ▫ More droughts widespread forest fire worsen air quality ▫ Change in how pollutants are dispersed. • Impacts on human health ▫ Changes in patterns of sickness and death. ▫ Respiratory problems affected by air quality change • Biodiversity ▫ Some species may grow too quick and overshoot their reproductive period (e.g. reef corals) ▫ Forest could be devastated if the rate of climate change outpaced the rate at which forest species could migrate. • Change in the pattern of ocean current Consequences of Global Warming Rising Sea Level Habitat Damage and Species Affected Increased Temperature Changes in Water Supply Melting ice and rising sea level Receding high mountain glaciers Ice shelves of the South Pole have partly separated and are collapsing. (NASA) What’s the proof that global warming is taking place? Portage Glacier • Alaska 1914 Photos: NOAA Photo Collection and Gary Braasch – WorldViewOfGlobalWarming.org 2004 Colorado River June 2002 Dec 2003 Global Atmospheric Concentration of CO2 Not everybody is convinced of the greenhouse gases - global warming theory • At this point, it appears that the warming itself is real – the surface temperature indeed becomes higher in the last few decades. • The question is – Is the warming caused by the greenhouse gases (especially CO2)? • Some groups, especially the IPCC members argue strongly for it. But there are other groups that are not convinced. The summary to the right is from Robinson et al. (1998). You can get IPCC reports at http://www.ipcc.ch/ Summary World leaders gathered in Kyoto, Japan, in December 1997 to consider a world treaty restricting emissions of ''greenhouse gases,'' chiefly carbon dioxide (CO2), that are thought to cause ''global warming'' severe increases in Earth's atmospheric and surface temperatures, with disastrous environmental consequences. Predictions of global warming are based on computer climate modeling, a branch of science still in its infancy. The empirical evidence actual measurements of Earth's temperature shows no manmade warming trend. Indeed, over the past two decades, when CO2 levels have been at their highest, global average temperatures have actually cooled slightly. You can get this from the following website http://www.oism.org/pproject/review.pdf Ozone Depletion Ozone Layer The ozone layer is found in the stratosphere ▫ It protects the Earth from ultraviolet rays emitted by the sun. ▫ The wavelengths of ultraviolet radiation are absorbed by the ozone molecules. Ozone absorbs uv-b radiation There is a natural cycle of formation and depletion of ozone What is the ozone layer? • The ozone layer is a layer of gas consisting of O3 molecules, called ozone, that forms when free Oxygen atoms bond to O2 molecules. Ultra-Violet Radiation • UV rays penetrate the Earth’s atmosphere at 3 slightly different wavelengths called UV-A, UV-B, and UV-C rays. So, why is the ozone layer important to life on Earth? • The stratospheric ozone layer completely stops the penetration of UV-C rays and eliminates most of the UV-B rays. • Therefore, the ozone layer protects life on Earth from the harmful effects of solar radiation on a daily basis. • Chlorofluoro carbons (CFC’s) and other halogenated hydrocarbons contribute to the destruction of stratospheric ozone. • Just one chlorine and bromine atom can catalyze the destruction of 100,000 ozone molecules • CFC’s (chlorofluorocarbons) • Other harmful compounds include HCFCs, halons, methyl bromide, carbon tetrachloride, NO2, and methyl chloroform. • CFCs were used in refrigerators, home insulation, aerosols, plastic foam, and throwaway food containers. Note: Both chlorine and bromine from halogenated hydrocarbons deplete the ozone. Ozone Depleting Chemicals • Chlorofluorocarbons (CFCs) • Methyl bromide • Halons • Methyl chloroform • Hydrogen chloride • Carbon tetrachloride • Linked to skin cancer – a deadly cancer • Linked to cataracts on the lens of the eye causing blindness So what might life be like without the ozone layer? UV light changes DNA in the skin, this can cause tumors, and can lead to cancer • Disruption of plant cycles and food chains ▫ May limit plant growth and change plant form, how nutrients are distributed, • Lowers levels of surface phytoplankton in the ocean • Damages the base of the ocean food chain • • • • • • • Limiting the use of CFC’s is difficult Ban the production and use of CFC’s Use CFC substitutes such as HCFC’s and HFC’s Recycling refrigerants Alternatives to gas-blown plastics Alternative propellants Alternatives to methyl bromide, a fungicide How does ozone depletion affect global warming and ultimately climate change? • As ozone levels in the stratosphere are depleted, more solar radiation penetrates the Earth’s atmosphere. • This affect results in an increase in solar radiation reaching the Earth’s surface adding to an increase in surface temperature. • In turn, global warming actually results in a warming of the troposphere, but a cooling of the stratosphere, hindering the ozone layer’s natural chemistry for repairs. • Montreal Protocol (1987): 30 countries agreed to reduce CFC, also encouraging other countries. ▫ Effectiveness: As a result of the Protocol, ozone-depleting gases have been reduced in recent years. Expected to be completely reduced by 2050. ▫ Countries are required to report annually on their consumption and emission of ozone depleting substances to the UNEP • London Convention (1990) • Copenhagen Protocol (1992) • Kyoto Protocol (1997) Research • What is the impact of climate change on pacific Island countries? How is Fiji affected? Has there been any research done to measure its impact? • Find out about : ▫ ▫ ▫ ▫ Montreal Protocol London Convention (1990) Copenhagen Protocol (1992) Kyoto Protocol (1997) (Is Fiji part of these initiatives ?)