What is causing warming of the earth?

Bloomberg has a great article showing why climate change deniers have it all wrong when they argue that the observed global warming is explained by natural causes. It just isn’t. The article is What’s Really Warming the World? Climate deniers blame natural factors; NASA data proves otherwise.

Here are the main points and graphics which compare the observed changes in earth’s temperature  with the changes expected from individual factors:

Natural factors

Changes in the earth’s orbit around the sun (blue line) have had a negligible effect on warming:

Sun

Changes in the sun’s temperature (orange line)have also had a negligible effect:

Solar

Volcanos influence the earth’s temperature, usually causing decreases,(red line) but cannot explain the observed warming:

Volcanic

Natural factors combined (earth’s orbit, sun temperature and volcanoes) (green line) cannot explain the observed warming:

Natural

Human factors

Changes in land use, like deforestation, (light green line) actually have a cooling effect:

Land-use

Ozone level changes (light blue line) have only a slight warming effect:

Ozone

Aerosol pollution (purple line) has had a marked cooling effect:

Aerosol

Greenhouse gas concentration increases (green line) have had a marked warming effect – it is clearly the main factor responsible for global warming:

Greenhouse-gases

When all the human factors, ozone, land use, aerosols and greenhouse gases, are combined the models (blue line) show a good agreement with observed temperature changes (black line):

Human

Natural and human factors combined

When all the natural and human factors are combined (red line) agreement between the modelling and observed earth temperatures is even better.

total

 

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