Global Change Notes

Global Change

  • Global change: Any chemical, biological, or physical property change of the planet.
  • Global climate change: Changes in the climate of the Earth.
  • Global warming: Warming of the oceans, land masses, and atmosphere.

The Greenhouse Effect

  • Incoming solar radiation:
    • 1/3 reflected back into space.
    • UV radiation absorbed by the ozone layer.
    • Strikes the Earth, converted to infrared radiation.
  • Infrared radiation absorbed by greenhouse gasses.
  • Greenhouse gasses radiate infrared radiation back to Earth.

Major Greenhouse Gases

  • Water vapor: Variable concentration, global warming potential <1, duration of 9 days.
  • Carbon dioxide: 390 ppm, global warming potential of 1, highly variable duration.
  • Methane: 1.8 ppm, global warming potential of 25, duration of 12 years.
  • Nitrous oxide: 0.3 ppm, global warming potential of 300, duration of 114 years.
  • Chlorofluorocarbons: 0.9 ppm, global warming potential of 1,600 to 13,000, duration of 55 to >500 years.

Sources of Greenhouse Gases

  • Natural:
    • Volcanic eruptions: mainly carbon dioxide.
    • Methane: from decomposition.
    • Nitrous oxide: from denitrification.
    • Water vapor.
  • Anthropogenic:
    • Burning of fossil fuels.
    • Agricultural practices.
    • Deforestation.
    • Landfills.
    • Industrial production (e.g., CFCs).

CO2 Levels

  • CO2 measurements started in 1958 by David Keeling

Temperature Changes

  • Since 1880, temperatures have increased by 0.8°C.

Measuring Past Temperatures

  • Changes in species compositions.
  • Chemical analyses of ice.

CO2 and Temperature Relationship

  • Increase in atmospheric CO2 leads to greater warming capacity.
  • Higher temperatures cause oceans to release CO2.

Consequences of Global Warming

  • Melting of polar ice caps, Greenland, and Antarctica.
  • Melting of glaciers and permafrost.
  • Rising sea levels.
  • Heat waves and cold spells.
  • Changes in precipitation patterns and storm intensity.
  • Shifts in ocean currents.
  • Impacts on plants, animals, and humans.

Controversy of Climate Change

  • The fundamental basis of climate change is not in dispute among the vast majority of scientists.
  • Uncertainty remains regarding the extent of temperature increase due to feedback loops.

IPCC Assessment

  • Assessment of global change by the Intergovernmental Panel on Climate Change (IPCC).

The Kyoto Protocol

  • In 1997, an agreement to reduce emissions of greenhouse gases from industrialized countries to 5.2% below their 1990 levels by 2012.
  • Developing nations did not have emission limits.

Carbon Sequestration

  • Involves removing CO2 from the atmosphere.
  • Methods include storing carbon in agricultural soils or land.
  • Capturing CO2 from power stations and emission sources for storage.