Greenhouse Effect

Greenhouse Effect Without climate system, Earth much colder than it is Climate system traps Sun’s energy; distributes heat around world Warming process called ‘Greenhouse Effect’ Recall: UV from sun; IR from ground Greenhouse gases in atmosphere absorb radiation from Earth’s surface and radiate it out in all directions Half of IR radiation sent back to Earth

Greenhouse Gases Air mostly N and O – don’t absorb radiation Gases that do absorb IR are called greenhouse gases (mostly H2O and CO2) Also methane (CH4) , ozone (O3) and nitrous oxide (N2O)

Carbon Dioxide Atmosphere contains 385ppm CO2 (0.0385% of gases) Estimated to cause up to a quarter of natural greenhouse effect on Earth – volcanoes, burning, cellular respiration of plants and animals

Carbon Cycle Movement of C through living things Oceans and living things remove CO2 from atmosphere and store C atoms in different form – called carbon sinks Eg. Plants use CO2 in photosynthesis; ocean sediment is solid calcium carbonate (like in seashells)

Water Vapour Causes roughly two-thirds of natural greenhouse effect Quantity depends on temperature – up to 4% Higher temp., more water vapour in atmosphere Relationship called a feedback loop

Greenhouse Effect How do greenhouse gases trap IR? N and O are diatomic atoms (2 of same atom); vibrate back and forth Water, carbon dioxide and methane have 3 or more atoms; wiggle in many ways and hit more energy waves