4.4 Climate change

4.4 Climate change

Lesson one- Understanding the link between global warming and the enhanced greenhouse effect

Objectives: Explain how the enhanced greenhouse effect can lead to global warming.

Keywords:

  • Global warming: An overall increase in global temperatures.
  • Greenhouse effect: the reabsorption of long-wave radiation (heat) by greenhouse gases.
  • Greenhouse gas: a gas than can re-absorb long-wave radiation and therefore contribute to the greenhouse effect.
  • Climate change: Changing of regional weather patterns.
  • Long-wave radiation: radiation with a relatively long wavelength (infra-red, or heat).
  • Short-wave radiation: radiation with a relatively short wavelength (visible light, ultra-violet light)

The greenhouse effect is a natural process which is important in maintaining a global average temperature which is suitable for life  (15 degrees C). Without the greenhouse effect, the average temperature would be a freezing -18 degrees C (according to NASA).

How does it work?

  1. A mixture of long and short-wave radiation from the sun reaches the Earth’s surface.
  2. Some of the short-wave radiation is reflected back into space.
  3. The radiation that reaches the Earth’s surface causes it to warm, and emit long-wave radiation
  4. Greenhouse gases re-absorb long-wave radiation, trapping it in the Earth’s atmosphere.
  5. This raises the Earth’s atmosphere to an average temperature which is suitable for life.

Simple explanation:

 

Another explanation:

 

The Enhanced Greenhouse Effect

It has been shown through studies of the Earth’s history that sometimes the average temperature of the Earth’s atmosphere can rise because of increased levels of greenhouse gases. The most important greenhouse gases have been carbon dioxide and water. Other greenhouse gases include methane, and oxides of nitrogen (eg.nitrous oxide NO2).

Although there are other factors that may also affect the changes in global temperature (eg. sunspot activity), there is currently a global concern that the climate is changing because of global warming, due to an enhanced greenhouse effect (more greenhouse effect), because of anthropogenic sources of atmospheric carbon dioxide and methane.

The two most important pieces of evidence for this are:

1) Manua Loa Observatory, Hawaii. 57 years of data on changes in atmospheric CO2

imagecredit:wikipedia

imagecredit:wikipedia

Q) Why is there a seasonal change (fluctuation?)

Q) What is the overall change?

Q) What evidence is there that this is causation?

 

2) Ice core data, such as the European project for ice coring, which combine northern atmosphere average temperature and carbon dioxide levels

image credit: British antarctic survey

image credit: British antarctic survey

Q.) Describe the trends shown in the data above

Q.) Evaluate this data as evidence of man-made global warming.

 Lesson two- Understanding the argument for global warming

Objectives: to evaluate counter-claims against the theory of man-made global warming. To learn that scientific arguments should be made using data from reliable sources, should not be biased, and should include uncertainties.

Keywords:

  • Global warming: An overall increase in global temperatures.
  • Climate change: Changing of regional weather patterns.
  • Ozone-layer depletion: A reduction in the amount of ozone at the stratospheric level. This is a separate issue to global warming

 

Activity A: Watch extracts from Al Gore’s film: the Inconvenient truth, and from the film ‘The great global warming swindle’. Try and list key claims made, and the evidence presented to support the claims. Try and have arguments from both sides.

Steps of a scientific argument:

1- Isolate the part of the claim relating to scientific theory

2-Discern the evidence backing the claim

3-Evaluate the source of the claim

Links:

The great global warming swindle https://www.youtube.com/watch?v=52Mx0_8YEtg

Debunking the great global warming swindle https://www.youtube.com/watch?v=p6rXVq_Y-PU

And this on the CO2 and temperature relationship https://www.youtube.com/watch?v=zQ3PzYU1N7A

The Effects Of Global Warming

Global warming means an average increase in atmospheric temperatures worldwide. This does not mean that the temperature will increase in every country however, the implications are far more complex and involve regional changes in climate (climate change).

Effects which have already been detected include:

-Melting of polar ice cap (Arctic)

-Melting of alpine glaciers (eg. Kilimanjaro). What are the global implications of this loss? (hint: see photo below)

-Rising sea levels

-Decreasing pH of surface layer of world’s oceans due to dissolving CO2. This has the effect of dissolving the carbonate skeleton of coral reefs

-Changing weather patterns (this can cause crop yields to improve or to decline in a specific area)

-Changes in migration behaviour eg. birds may not move in the way they used to during summer / winter

-Changes in species ranges ie. where species can live. Two examples of this would be that mosquitoes and other pests would be able to extend further north, and predators may be able to hunt further north than they used to.

-Species extinction eg. Golden Toad in Monteverde

– More extreme weather events eg. tsunamis, hurricanes. This is because of the relationship between energy flow between the atmosphere and the world’s oceans.

-Acidification of oceans, leading to decalcification and weakening of coral reefs

-Bleaching and die-off of coral reefs, due to temperature rises of more than 2 degrees C in the ocean.

 

Lesson 2 – Global warming simulation lab

 

Extra materials:

Revision powerpoint

 

 

Climate change and Global warming

this is a simple and colourful explanation of how the enhance greenhouse effect can lead to global warming. It comes from the documentary ‘An Inconvenient Truth’ by Al Gore.

 

 

The role of CO2 in global warming.

 

 

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