The sun radiates energy and is absorbed by the earth which re-emits infra-red radiation. Gases that stop infrared radiation escaping from the earth are greenhouse gases. This keeps the earth warm enough for life and is called the greenhouse effect.
- Methane is produced through anaerobic decay of organic matter, domestic waste in landfills, belching of animals and combustion of fossil fuels. As temperature increases, methane will be released from natural stores
- A rise of carbon dioxide levels in the atmosphere and global warming are linked, there is evidence supporting the theory. Carbon dioxide is increasing due to burning of fossil fuels, changes in the Earth’s orbit, solar radiation, volcanic eruptions and deforestation. Measured using ice core samples, bubbles trapped in ice contain carbon dioxide so levels can be measured.
- Aerosols are very small particles in the atmosphere
Other factors of climate change are:
- Degree of reflection from ice and snow
- Extent of cloud cover
- Changes in sun’s radiation
Extrapolation = extending a line on a graph – we assume there is enough data to establish the trend accurately and present trends continue. Extrapolation is often the basis for predictions.
Computer models can get it wrong because:
- Limited data or (computer) knowledge
- Failure to include all factors affecting the climate
- Changing trends in factors
Impacts of global warming:
Changes to species distribution
Climate change may cause a shift in plant distribution. Some may benefit and dominate while others may be lost from the community. As the average temperature rises, species migrate closer to the equator. Species may colonise new areas, out-competing existing species, making them extinct. Other factors affect species distribution such as change in rainfall pattern, soil moisture, winds and rising sea levels.
Changes to development
In many reptiles, temperature affects the sex – global warming could cause a change in sex ratios of these species.
Changes to life cycles
The rate of metabolic reactions will change. Insects may get through their life cycles quicker and be ready to feed on plants that are not yet mature. Plants may flower earlier or later.