2The Natural Greenhouse Effect Greenhouse gases prevent thermal energy from getting to Space.Radiation from the Sun passes through the Earth’s atmosphere and is absorbed by the Earth’s surfaceBecomes thermal energy and Earth warms upEarth’s warm surface emits lower-energy IR radiationGases in the atmosphere trap this radiationGHGs in atmosphere absorb radiation and some is sent back to Earth’s surfaceThis is called the Natural Greenhouse Effect
4Greenhouse GasesA greenhouse gas (GHG) is any gas in the atmosphere that absorbs lower-energy infrared radiationGreenhouse Gases:Water vapourCarbon dioxideMethaneOzoneNitrous oxides
5Water Vapour Most significant contributor to the natural greenhouse effectResponsible for 65 – 85% ofgreenhouse effectAdded by evaporation, human activityhas little impact.Relationship to temperature:Water evaporates more readily when it is warmerWarmer air can hold more water vapourTherefore, as Earth’s temperature rises, more liquid water becomes water vapourThe more water vapour there is, the warmer the earth becomes.This is called a positive feedback loop
6Carbon DioxideLiving things and the oceans are carbon sinks they absorb carbon dioxide from the atmosphere and store it in another formMain natural source is animal respiration and main human source is burning fossil fuels. Plants can clean this carbon dioxide from the air as part of the carbon cycle (photosynthesis), but the more deforestation and urbanization that occurs, the less plants there are to carry out this task.
7The effects of water and carbon dioxide amplify each other The effects of water and carbon dioxide amplify each other. If CO2 causes a temperature increase, there is more evaporation which then also causes more of a temperature increase. The same positive feedback loop applies to cooling.
8Methane Much less methane in atmosphere than CO2 in the atmosphere BUT… a methane molecule can absorb more thermal energy than that of CO2Bacteria that break down waste produce methane and these bacteria mainly exists in bogs and swamps. Human sources include landfills and oil processing sites.
9Ozone (O3)In the stratosphere, ozone acts to absorb UV radiation, protecting the EarthIn the troposphere,ozone acts as agreenhouse gas
10Ozone in the Stratosphere Ozone protects us from ultraviolet radiation and the atmospheric ozone layer in the stratosphere is declining.Chlorine destroys ozone and humans have released a lot of chlorine into the atmosphere from the use of chlorofluorocarbon (CFC) and Freon in many refrigerants and air conditioners, amongst other applications.These halocarbons stay in the atmosphere for a long time. Even though many nations banned their use in the late 80’s they are still present.
11Ozone in the Troposphere Ground level ozone is a significant personal health issue.Hydrocarbons and nitrous oxides create ground level ozone forming smog in major urban centres, like Toronto.The combination of ground level ozone and warm temperatures means health warnings are required because it is too hard to breath outside.
12Nitrous OxidesSmaller concentration in atmosphere, but more effective as a greenhouse gasNaturally produced by reactions between bacteria and the soil and waterNatural sources include tropical soil and oceans (recall the nitrogen cycle). Human sources include fertilizer, sewage treatment and car exhaust.
13Other factors effecting the Greenhouse effect Human activities!!
15The Anthropogenic Greenhouse Effect Anthropogenic means originating in human activity.
16Global WarmingScientists measure the amount of one substance that is mixed with another using concentration.For about the past 50 years scientists have been measuring the concentration of CO2 in the atmosphere.When we talk about the concentration of gases, we usually talk about parts per million (ppm).Example: CO2 levels in 1960 were 315 ppm. This means that there were 315 mg of CO2 for every kg of air. Another way of saying this is that for every million units of atmosphere there are 315 units of CO2. According to co2now.org, in December 2010 the concentration of CO2 was ppm.
17Anthropogenic Greenhouse Gases The anthropogenic greenhouse effect is the increased capacity of the atmosphere to absorb and trap thermal energy because of the increase in greenhouse gases caused by human activity.Processes that add greenhouse gases to the atmosphere are called sources. Processes that absorb greenhouse gases are called sinks. Figure 1 shows the human sources of carbon emissions and the sinks that carbon goes into.
19Humans and Methane METHANE: <20% of anthropogenic greenhouse effect Comes from:Agricultural activities such as rice farming and cattle ranchingDecay of organic material in landfills and sewage treatment plantsCoal mining and natural gas extraction release trapped methaneDeforestation
20Humans and Other Gases NITROUS OXIDE: <10% From livestock feed, waste management and fertilizersCFCsRefrigeration agents (in fridges and air conditioners)
21So What Can We Do?There are several ways for humans to reduce our greenhouse gas emissions. These include, but are not limited to:Conserving electricity: lights off and unplug those chargers!Improving home-heating efficiency: new furnaces, digital thermostats and sealing up windowsREDUCE, reuse and recycle: this applies to so many things! For starters – stop wasting paper! Print double sided and use narrow margins on your page. Print only once.
22HomeworkTake this energy quiz now and test your knowledge of energy use leading to greenhouse gas emissions. [Application]Come up with 3 simple things you can do in your own home to reduce the impact of your greenhouse gas emissions. These can include both decreasing sources and adding sinks. All three should be inexpensive and easy to implement. [Application]