In order to understand discussions of global warming, you need a few basic scientific facts. I’m stripping them down so they’re easy to remember.
Thermodynamics is an imposing word that means “movement of heat.” Thermodynamics fundamentally establishes boundaries on what chemical reactions can take place and what other kinds of work can be done. Facts derived from thermodynamics cannot be bent or gotten around. Heat is a type of energy, so I’ll use the two words interchangeably here.
Fact #1: Carbon dioxide and water result from the production of energy by burning fossil fuels. In order to make them into something else, energy must be supplied. Not only that, but more energy must be supplied than was produced by burning, sometimes a lot more.
Any claim that a process can turn carbon dioxide back into fuels, or that water can supply hydrogen as a fuel, should be met with the question “Where does the energy come from?” If the answer is non-carbon power, the claim may be worth pursuing. If the claim says nothing about energy sources, more information is needed.
Fact #2: Separating something from a mixture requires energy. The lower the concentration, the more energy is required.
Carbon dioxide is about 400 parts per million in the atmosphere, or 0.04%. That is a very low concentration. Any claim of taking carbon dioxide out of the atmosphere should be met with that same question, “Where does the energy come from?”
Windmills get their energy from wind, solar cells from sunlight, and plants and algae from sunlight. Some of the schemes involving them may seem to counter Facts #1 and #2, but careful energy tracing will show that they do not.
Electricity and hydrogen, while clean in their immediate area, are only as clean as their sources. They are energy carriers rather than energy sources – they put a source of energy, say a nuclear reactor, into a form you can tuck into your car or home.
That’s all the thermodynamics you need to understand most of global warming.
Video from National Geographic.