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Evidence for Global Warming
(1) Temperature records
- Since the 1850’s, temperature has been measured around the world using thermometers.
- This is very reliable, but only a short term record of global temperature change.
(2) Dendochronology
- Using tree rings to work out how old a tree is.
- Most trees produce one ring within their trunks every year, and the thickness of the ring depends on the climate when the ring was formed, when it is warmer the rings are thicker.
- Scientists can then date each ring and see what the climate was like for each year.
- It cannot give very accurate results at all, just an estimate of the climate.
(3) Pollen in peat bogs
- Pollen can be preserved in peat bogs, and they accumulate in layers, so the age of the pollen increases with depth.
- Scientists can take cores and extract pollen grains to identify the species the pollen came from, and this can give an estimate of climates, as only mature trees would produce pollen, so the climate then would have to have been favourable for those trees.
(4) Frozen Isotopes
- Ice cores from the Antarctic is quite accurate.
- Air is trapped in the ice, and the proportions of isotopes in the ice reflect the air temperature at the time that the layer was laid down.
- This data can go back as far as 3000000 years.
Causes of Global Warming
When it comes to A2/A-level Biology, do you still remember the term "greenhouse effect"?
- Greenhouse gases, like carbon dioxide and methane contribute to the greenhouse effect.
- The greenhouse effect is when radiation from the sun is reflected back from the earth as infrared radiation, which is absorbed by the greenhouse gases in the atmosphere. Thus, maintaining the temperature at a higher level.
- With an increasing level of greenhouse gases, global temperatures are rising.
- Humans are enhancing the greenhouse effect by burning fossil fuels, which produces carbon dioxide, and destroying carbon sinks, like trees.
- Methane levels are also rising because of greater fossil fuel extraction, and more decaying waste, as well as greater amounts of cattle for food, which give of methane as a waste gas.
Effects of Global Warming
(1) Rising temperature
- This will affect the metabolism of all organisms as enzymes denature once past 40 decrees Celsius.
- It will also affect the distribution, as conditions in their habitat may change, and they may not be able to survive the change, so will have to move out of that area
(2) Changing rainfall patterns
- Some areas may get more rain, some may get less, this will affect the lifecyles of some plants and distribution of species, e.g deserts could increase in area because of decreases in rainfall.
(3) Changing seasonal cycles and life cycles
- E.g. mating periods start earlier for some organisms because of change in seasons meaning earlier availability of food.
- Distribution of organisms will change.
Reducing Global Warming
- Using biofuels, which are produced from biomass, so there is little net increase in carbon dioxide production, because of the amount taken in when the material was growing.
- Reforestation, planting new trees to take in carbon dioxide by photosynthesis.
- Renewable energy sources, such as wind turbines.
Extrapolation
- Past data can be extrapolated to make predictions about the future, using scenarios, such as emissions growing as they are now, emissions increasing, emissions being controlled by management strategies.
That's the end of the topic!
Drafted by Bonnie (Biology)