Why is the Earth 32°C warmer than the moon? Because the Earth has an atmosphere, and so a greenhouse effect.

The Greenhouse Effect

The Greenhouse Gases There are five main greenhouse gasses. Gas Concentration in atmosphere (ppm) Greenhouse gas? Nitrogen (N2) Oxygen (O2) Water vapour (H2O) Argon (Ar) Carbon dioxide (CO2) Neon (Ne) Helium (He) Methane (CH4) Krypton (Kr) Hydrogen (H2) Nitrous oxide (N2O) Carbon monoxide (CO) Xenon (Xe) CFCs 780,000 209,000 ~20,000 9,000 380 18.2 5.2 1.7 1.1 0.6 0.3 0.1 0.09 0.000 06    Greenhouse effect from Sumanas

The concentrations of many of the greenhouse gases have increased over the past 200 years. And so has the average global temperature.

Global temperature reconstructions We can reconstruct the Earth’s temperature from ice cores going back thousands of years. The Earth’s temperature is the highest it’s been for at least 1,000 years. Shaded regions = ice cores Solid line = direct measurements

The Enhanced Greenhouse Effect Recently the five greenhouse gases have been increasing due to human activities: Burning fossil fuels releases CO2, H2O and N2O Farming cows and rice releases CH4 due to methanogenic bacteria in the anaerobic conditions in cows’ rumens and flooded paddy fields. Deforestation releases CO2 and CH4. Industry makes CFCs (ChloroFluoroCarbons), synthetic chemicals used in fire extinguishers, aerosols and refrigerators. These changes are causing the enhanced greenhouse effect. Global warming from EPA

Global Warming This increase in greenhouse gases is causing a rise in mean temperature of a few ºC, called global warming. Global warming may cause: Changes in distribution of animals and plants as their habitats warm, so they migrate towards the poles. Extinction of animals and plants that can’t migrate. Rising sea levels and flooding as a result of melting ice caps and expansion of the oceans Changes in the water cycle, causing unpredictable and severe weather events. Changes in farming, as crops can’t grow or pests can survive.

Deforestation Deforestation is a triple whammy for the greenhouse effect: Photosynthesis by trees, which absorbs CO2, is reduced The felled trees are burned or left to decay, which both release CO2 The forests are often replaced by farms, which release CH4   In addition, deforestation causes other deleterious effects: Leaching. Without roots to absorb and cycle minerals, minerals are leached (washed) out of the soil into rivers to the sea. So the soil is less fertile for growing crops. Soil Erosion. Without roots to bind soil together, soil is carried away by rain (eroded). Water Cycle. Without trees to transpire, less water is evaporated from soil, so less water vapour is formed so less rain falls. Google maps

Deforestation for paper-making on the Indonesian island of Sumatra

Deforestation in Brazil's western state of Rondônia in 2000 http://earthobservatory.nasa.gov/Features/WorldOfChange/deforestation.php

Deforestation in Brazil's western state of Rondônia in 2010

Enhancing the Greenhouse Effect

White Lemuroid possum found in the cooler temperatures of the higher altitude rainforests of far north Queensland no sightings for three years 0.8ºC rise in average temperature responsible for its disappearance first mammal to become extinct due to man-made global warming “If they have died out it would be first example of something that has gone extinct purely because of global warming." Steve Jones, Researcher

United States Geological Survey scientists conservatively project that two-thirds of the polar bear population in the world could disappear by 2050, including all of Alaska's polar bears. Nature’s great events http://www.bbc.co.uk/naturesgreatevents/melt_timelapse.shtml BBC report on polar bears and global warming http://uk.truveo.com/climate-change-threat-to-polar-bears/id/1297270616