Energetics
Dissolution of most gases is exothermic. That is, when a gas dissolves in a liquid solvent, energy is released as heat, warming both the system (i.e. the solution) and the surroundings. The temperature of the solution then decreases to that of the surroundings. The equilibrium, between the gas as a separate phase and the gas in solution, will therefore (by Le Châtelier's principle) shift to favour the gas going into solution as the temperature is decreased. Thus, decreasing the temperature increases the solubility of a gas. When a saturated solution of a gas is heated, gas comes out of solution.
Read more about this topic: Enthalpy Change Of Solution