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 (H 2 O) 36-70% carbon dioxide (CO 2 )9-26% methane (CH 4 )4-9% ozone (O 3 )3-7% nitrous oxide (N 2 0)2-6%

Greenhouse Gases Nelson Science 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

3. Methane  1 molecule of CH 4 traps 23 times more GG than 1 molecule CO 2  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 CO 2  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  CO 2 – burning fossil fuels, deforestation  CH 4 – agriculture, mining, landfills  N 2 O – 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 1.Long Term Changes  thousands/millions of years  plate tectonics – continents drift changing wind and ocean patterns, collide forming new mtns

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

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

Short Term Variations  100’s – 1000’s of years 1.Volcanic Eruptions  put dust and particles in air - blocks sunlight and cools earth 2.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 Nelson Science