When fossil fuels are combusted, all the heat produced, used and wasted, ends up in the oceans, lakes, atmosphere and space. You may have noticed that weather temperatures near cities are warmer, because cities are ‘heat sinks’ of human activity, where waste heat is disposed of into the atmosphere. 

The heat wasted into the air by cities, agriculture, livestock, transport and by evaporation from water storages is large. If you live near a thermal power station, where river, lake or ocean water is used for cooling, you may have noticed the water is warmed up and can even cause fog at night. Alternatively, heat could be wasted from a cooling tower.

You may have been at an airport and felt warm ‘jet wash’, exhaust gases from a plane manoeuvring. 

There is evidence that human heat pollution is significant. By comparison with solar radiation received by Earth, the amount of thermal pollution is lower when the Sun is high, but at night thermal pollution contributes significantly to the daily heat balance, enough to cause global warming. I calculate that human-generated heat stays on Earth with an average residence time of 140 years. 

Substitution of solar, wind and hydro for fossil fuel combustion would not reduce thermal pollution and could increase it, if electrical output efficiency is lower and more heat is wasted and replaced from the Sun. 

The other theory, that global warming could be caused by heat entrapment by a tiny amount of carbon dioxide gas, is disputed in the literature, unnecessarily complex and without evidence. To reduce global warming, energy consumption must be reduced.

More information is in my book Animal Farm 2, on Amazon.

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