Climate Change

Greenhouse Gases

• greenhouse gases→gases found in the atmosphere such as water vapour, carbon dioxide, methane and nitrous oxides, that contribute to the greenhouse effect
• water vapour→water found in the atmosphere in a gaseous form. It is the most abundant greenhouse gas
• carbon dioxide→a gas found in the atmosphere that is a main greenhouse gas. carbon dioxide enters the atmosphere by respiration and decomposition as well as burning of biomass and combustion of fossil fuels. It is taken out of the atmosphere by the process of photosynthesis and absorption by water.
• for a gas to contribute to the greenhouse effect, it needs to be able to absorb a longer wavelength or infrared raditation.
• all greenhouse gasses combined make up less than 1% by volume of the Earth's atmosphere
• Certain gases in the atmosphere absorb radiation and retain heat, causing Earth's atmosphere to be warmed.

Sources of GHGs

Methane

• emmited from marshes and other waterlogged habitats
• landfill sites
• extraction of fossul fuels
• melting ice in polar regions

Nitrous Oxide

• released by bacteria in some habitats
• agriculture
• vehicle exhaust

Greenhouse Gases and the Wavelength of Radiation

• Summary of the four steps that explain the greenhouse effect:
• $Solar Radiation$
  • solar radiation from the sun passes through the ozone layer (the layer of the atmosphere which blocks UV radiation)
  • only short-wavelength radiation from the sun reaches the Earth's surface -
• $The Earth absorbs some of this shortwave radiation while some are reflected, which is then re-emitted as infrared (heat)/longwave radiation$
• $Greenhouse gases in the atmosphere absorb the longer wavelength radiation$
• $The greenhouse gases re-emit the absorbed light in all directions as heat.$
• $Some of this radiation is re-emitted towards the Earth, thus contributing to global warming.$
  • 
  • Without greenhouse gases, the Earth's temperature would be about -18 degrees Celsius.
• Greenhouse Gases: atmospheric concentrations
  • Implications of increase in global temperatures:
  • Climate change
  • rising sea levels
  • loss of habitat
  • biotic factors
  • frequent and stronger storms
  • precautionary principle→also known as the burden of proof, this principle states that even without concrete evidence of a causal relationship, precautionary measures should be taken to ensure that humans are not causing detrimental harm to the environment or human health.
• Carbon Dioxide and the Coral Reefs
  • coral reefs→a ridge in the ocean where living coral polyps attach and secrete calcium carbonate. Coral reefs are typically very diverse places found in warm shallow waters.
  • Due to the large amounts of carbon dioxide dissolved in oceans, the average pH level of oceans has decreased to about 0.11, causing ocean acidification.
  • Due to ocean acidification, the solubility of calcium carbonate increases (as it is soluble in acids/low pH solutions), decreasing the amount of calcium carbonate available to organisms.
  • marine organisms such as crustaceans, molluscs and corals require calcium carbonate to build their exoskeletons and shells, through calcification
  • without a sufficient supply of calcium carbonate, the speed at which coral reefs are built will slow down and they will also become more brittle, thus they become less resilient to other factors influencing their survival.
  • Many of the organisms affected by ocean acidification and a rise in temperature are important food sources for corals. Their destruction disrupts the food chain.
  • acidification of ocean > low carbonates > marine animals can't make exoskeleton > decrease in aquatic diversity