Board Thread:Questions and Answers/@comment-2600:387:5:803:0:0:0:90-20190713200400/@comment-38876330-20190723105523

Bit late but...

Pyrokinetics decompose air molecules and synthesize the parts into fuel bonded with oxygen molecules. They then increase the temperature of the fuel, which is a measure of its thermal energy (vibraitonal kinetic energy), until ignition is achieved. This would be the scientific rationale behind their skill, but energy is being violated in doing so because espers are supernatural, as implied by the previous respondant.