Greenhouse Gases & Human Activitites

Greenhouse Gases & Human Activities Greenhouse gases in the atmosphere produce a warmer Earth. CO2 concentration has increased from 315 ppm in 1960 to 370 ppm in 2000. ppm = parts per million (parts of one substance for 1,000,000 parts of another)

Greenhouse Gases & Global Warming 99% of the atmosphere is made of N2 and O2, but neither are greenhouse gases! Greenhouse gases (GHGs) are gases that absorb and re-emit infrared radiation. Made up of 3 or more atoms Interact with radiation of different wavelengths Produce warming by absorbing and emitting energy Most abundant: carbon dioxide and water vapour

Sources & Sinks Processes that add greenhouse gases to the atmosphere are called sources. CO2 comes from natural sources such as animal respiration, and human causes such as combustion of fossil fuels and deforestation. Process that absorb greenhouse gases from the atmosphere are called sinks. Plants convert CO2 into stored carbon during photsynthesis, phytoplankton in the oceans absorb 30-50% of CO2 from burning of fossil fuels.

Composition of Earth’s Atmosphere

Water Vapour as a Greenhouse Gas Water vapour accounts for 65-85% of the greenhouse effect But… it is not caused by humans!!! The concentration of water vapour in the atmosphere at any one time is directly related to TEMPERATURE.

Interaction of Water Vapour & Carbon Dioxide The effect of one is added to the effect of the other Positive feedback loop

Sources of Methane (a GHG) Methane (CH4) is produced by bacteria that break down waste matter in oxygen-free environments: Wetlands (bogs, swamps) Rice paddies Digestive processes of termites and cattle Decomposing garbage in landfills Processing of coal and natural gas Tanks of liquid manure from livestock production

Unique Ways of Capturing Carbon from Methane Having cattle wear backpacks to capture methane, which could then be used as fuel Feeding cattle clover and alfalfa to reduce emissions by 25% Switch in human diets (stop eating beef)

Ozone Depletion & the Ozone “hole” Large region of declining ozone (O3) concentration since 1970 Due to addition to the atmosphere of human-made gases that contain chlorine Results in increase in amount of UV light that reaches Earth’s surface Positive feedback loop Causes stratosphere to cool  formation of polar stratospheric clouds  formation of free chlorine  reduction in ozone

Ground-Level Ozone Smog from reaction of sunlight and vehicle exhaust chemicals Can cause damage to lungs and heart Produces cracks in rubber and plastic Can trap thermal energy, contributing to global warming

Halocarbons Chemicals formed by industrial processes from carbon and one or more halogens Best-known: chlorofluorocarbons (CFCs) Solvents, cleaners, coolants Absorb infrared radiation Break apart ozone Banned in most developed nations since 1987

Anthropogenic Greenhouse Effect Increased capacity of the atmosphere to absorb and prevent the escape of thermal energy because of an increase in greenhouse gases introduced by human activities

Global Warming Potential (GWP) Ability of a substance to warm the atmosphere by absorbing thermal energy Depends on: Concentration of the gas in the atmosphere Ability of the gas to absorb heat Length of time the gas remains in the atmosphere

How Can We Reduce Greenhouse Gas Production? Conserve electricity Energy-efficient light bulbs and appliances Improve home heating efficiency Thermostat settings, insulation Reduce, re-use, recycle Garbage

Homework Pg. 326 #1-4 Pg. 329 Activity 8.3 Pg. 330 #5-8 Pg. 332 #1-8