THE GREENHOUSE EFFECT Greenhouse Gases: chemical compounds in the atmosphere that trap heat they retain a proportion of the sun’s heat through the greenhouse effect. 5 major greenhouse gases: Gas % of Greenhouse Effect water vapour (H2O) 36-70% carbon dioxide (CO2) 9-26% methane (CH4) 4-9% ozone (O3) 3-7% nitrous oxide (N20) 2-6%

Greenhouse Gases Nelson Science Water Vapour: ~ 60% of GG quantity of water vapour depends on the temperature of the atmosphere they are connected through a positive feedback loop

2. Carbon Dioxide ~ 25% of GG produced from natural and human sources volcanic eruptions, burning fossil fuels, cellular respiration in plants and animals and decomposition carbon sinks – oceans and plants that absorb carbon dioxide from atmosphere and store it in a different form

The Carbon Cycle

5. Nitrous Oxide (ha ha ha) 3. Methane 1 molecule of CH4 traps 23 times more GG than 1 molecule CO2 from plant decomposition in swamps and animal digestion 4. Ozone acts as GG in troposphere when it combines with exhaust creating smog 5. Nitrous Oxide (ha ha ha) 300 times more powerful GG than CO2 from natural and human sources released by bacteria in soil and water released in emissions from cars and factories

Anthropogenic GG GG always been part of our atmosphere major increase in past 200 years due to human activity called anthropogenic GG CO2 – burning fossil fuels, deforestation CH4 – agriculture, mining, landfills N2O – animal feed and wastes, fossil fuels

Short and Term Changes to Climate earth is 4.6 billion years old climate is constantly changing depending on how much of Sun’s energy gets absorbed Long Term Changes thousands/millions of years plate tectonics – continents drift changing wind and ocean patterns, collide forming new mtns

Ice Ages - past 800 000 years earth cycled between ice ages and warming periods

Causes: Eccentricity - Earth’s orbit varies from elliptical to circular, 100 000 yr cycle Tilt – tilts back and forth on axis, 41 000 yr cycle Wobble – slowly wobbles as it spins on its access, 23 000 yr cycle

Short Term Variations 100’s – 1000’s of years Volcanic Eruptions put dust and particles in air - blocks sunlight and cools earth Air and Ocean Currents thermohaline circulation affected by fresh water from melting glaciers El Nino/La Nina – change in direction of prevailing winds changing ocean currents, occurs every 3-7 yrs

Feedback Loops the problem creates and effect that impacts the original problem Positive Feedback – effect increases original problem Negative Feedback – effect decreases original problem. eg. thermostat controls temp

Water Vapour Feedback water vapour enters the atmosphere when the climate warms up. it’s a GG, so causes the climate to warm up even more. if the climate cools down, less water vapour forms and the climate cools further

Albedo Effect proportion of radiation reflected by a surface ice has a high albedo because it reflects back most UV rays If Earth’s average temperature drops slightly, more ice forms. reflects more of the Sun’s radiation, and Earth’s temperature decreases even more If Earth’s average temperature increases, more ice melts. More of the Sun’s radiation is absorbed, and Earth’s temperature increases more. Nelson Science