More on the Greenhouse Effect


Global Carbon Dioxide emissions

Government Failure and Private Progress

An excellent introduction to the Greenhouse Effect for children can be found on the North American Space Agency website:

The following excellent graphic can also be found, with additional material, on the website:

THE SUNS RAYS (INSOLATION, short-wave radiation) pass through the atmosphere and turns into heat energy when the light rays hit the ground. The ground is warmed and some of the heat radiates upwards into the atmosphere as heat energy (infra-red, long wave radiation). Some of this heat leaves the earth’s atmosphere but some of it is absorbed by greenhouse gases such as carbon dioxide, methane, nitrous oxide and also by water vapour.

Of the incoming radiation from the sun:

  • 26% is reflected back to space by the atmosphere and clouds.
  • 19% is absorbed by the atmosphere and clouds.
  • 55% reaches the earth’s surface where much is absorbed as heat.

Clouds, and areas of snow and ice, have a high albedo, which means they reflect back much incoming radiation. The reflected heat is absorbed by greenhouse gases. Their molecules start to vibrate and are warmed. This holds escaping heat in the atmosphere, where much is radiated back to ground or absorbed by other greenhouse gas molecules before, finally, escaping to space.

Carbon Dioxide is made of one atom of carbon and two of oxygen. CO2 molecules make up a small fraction of the atmosphere but have a large effect on climate. At the start of the 19th Century the carbon dioxide content of the atmosphere was 270 ppm. Today it is above 400 ppm. This causes a huge increase in the heat retaining properties of the atmosphere.

Methane has one carbon and 4 hydrogen atoms. It is a bigger molecule and can absorb even more heat than CO2. Although there are low concentrations in the atmosphere it has a big impact on warming.

Carbon dioxide has increased with the burning of fossil fuels, such as coal and oil. Methane is emitted from the digestive systems of farm animals, such as cows, goats and sheep, which release the gas which is produced during the digestion of grass and other plant matter. When cement is made from limestone, a huge amount of CO2 is released.

Higher concentrations of greenhouse gases keep more heat in the atmosphere and cause air and ground temperatures to rise.

The contribution of each gas to the greenhouse effect is:

  • Water vapour 36-70%
  • Carbon dioxide 9-26%
  • Methane 4-9%
  • Ozone 3-7%


Global Carbon Dioxide and Greenhouse Gas emissions

The graph below shows the huge rise in carbon dioxide and greenhouse gas concentrations in the atmosphere since 1700.


Record Emissions

  • CO2 concentrations are at their highest ever levels of 400ppm.
  • Global emissions of CO2 from human activities are over 36 billion tonnes per year and rising.
  • The contribution of other greenhouse gases, such as methane, has also grown rapidly.
  • There is a 100-fold difference in per capita emissions between the most polluting and the least polluting countries.
  • The largest annual emitters of CO2 at the present time are: China 25%, USA 15%, EU 10%, India 7% and Russia 5%.
  • The countries which have contributed most CO2 to the atmosphere since the industrial revolution began are: USA 25%, EU 22%, China 13%, Russia 6%, Japan 4%.
  • The world is not on track to meet its agreed target of limiting warming to 2 degrees C. Under current policies, the earth’s atmosphere is on track to heat by well-over 3 degrees (3.1-3.7 degrees).

Much of China’s emissions are made producing goods for consumers in other countries.
By getting goods produced in China countries are exporting carbon-based manufacture.


Government Failure and Private Progress

Failed Paris Agreement of 2015

To prevent another 1.5 degrees of warming the world needs to reduce carbon emissions by 7.6% every year until 2030. Every year we delay the greater the cutbacks have to be in future. At the Paris Agreement of 2015 of the UN Climate Change Convention governments would only agree to try to limit warming to 2 degrees – yet many scientists believe that countries will fail in even this modest goal and it will have devastating consequences for the Earth’s climate and ecology:

  • A 1.5°C rise will cause 70% of coral reefs in the oceans to die, but a 2-degree rise will wipe out most of the coral, which is a home and breeding ground for much ocean life.
    • There will be a dramatic decline in the insects that are vital for pollinating crops and plants.
    • The Arctic Sea ice will melt and disappear in the summers.
    •  A rise in sea levels and the flooding of coastal cities – which could affect up to 10 million people.
    • A rise in temperature of 2 rather than 1.5°C will cause sea level to rise an extra meter.
    • Extreme weather events will increase everywhere – more powerful storms, more torrential rain, more floods and, in between, longer periods of drought.
    • Crop failure will cause serious food shortages and famine in some areas.

Progress by Private Citizens

People across the world have become frustrated by the lack of progress by their governments and they are taking action themselves to reduce their carbon footprints. They are moving away from using carbon-based fuels, getting energy from renewable sources and reducing the total energy they consume:

  • Families are moving away from carbon-based energy sources by:
    • fitting solar photo-voltaic (PV) panels on their homes to generate clean electricity and selling any surplus they generate to their national electricity companies. (e.g. 800,000 homes in the UK)
    • Others are fitting solar thermal panels which generate hot water directly from the sun. (e.g. 250,000 homes in the UK)
    • Homes are drawing hot water for warming their homes from ground source heat pumps.
  • Households are choosing to buy electricity from companies that generate power from renewable, clean sources of energy, including
    • Hydro-Electric Power (HEP). Uganda generates most of its power by harnessing the force of water in the River Nile to produce electricity from turbines.
    • Wind Power. In windy parts of the world wind turbines are becoming important as a source of renewable energy. In the UK, for example, over 20% of electricity is generated from wind and the percentage is rising rapidly.
    • Bio-mass Power Stations – these are thermal stations that burn wood or animal dung to make electricity, but the wood comes from renewable sources, so the new growth removes all the carbon that is created by the thermal power station.
  • Industry and power stations are exploring the use of carbon capture, where carbon dioxide from combustion is pumped into underground storage sites, such as geological structures (anticlines) that once held petroleum.
  • More families and firms are buying electric cars and there is a plan in Europe to phase out all diesel and petrol cars and lorries between 2030 and 2040.
  • People are switching to energy-saving lights. Lights based on Light Emitting Diodes (LED) use 75% less energy and last 20 times as long.
  • More people are cutting the distances and times they travel by car, bus or by air and there is more car sharing by those making regular journeys.


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