If two things vary in parallel, that is a positive correlation.  But it does not prove that one causes the other. For example, wet roads always occur when it rains. But wet roads do not cause rain. Three things are required to prove that rain always causes wet roads. Firstly, no exceptions -- roads must get wet every time it rains.  They do. Secondly, the cause must come before the effect.  Rain comes before wet roads (apart from snow, floods, burst water-mains etc). Thirdly, we need a credible explanation of the mechanism.  We have it -- rain is composed of falling drops of water, and the water wets the road. The three conditions are satisfied -- therefore, rain does cause wet roads.  The theory becomes a law. Now, let's look at the theory that carbon dioxide (CO2) controls global temperature. Firstly, there is no consistent correlation -- CO2 has risen consistently for the last century, but global temperatures rise...(Read Full Post)