The chance of Global Thermo-Nuclear War, not "Global Geothermal Nuclear War" varies in this modern day world. The reason I say this is because world leaders are too good at their jobs to let this happen. "A nuclear war cannot be won and must never be fought." - Ronald Reagan. This observation is very accurate and somewhat profound. War is an extension of political policies, take for example the war in Iran as Tom has described well, it is motivated by political interest more than security. If war was to proceed without political purpose it would degenerate into purposeless destruction, or total war. Using Nuclear power to impose political position is an outrageous act, no person elected by a free nation would get away with such a threat to global security. the consequences of such choices are unthinkable. During the Cold War where Nuclear war was imminent, the concept of not firing your missiles was described as MAD, Mutually Assured Destruction. No one could make the step towards Nuclear war because the outcomes would be too frightening. In some cases though we have people with Nuclear capabilities who have not come to power by the election of their nation. These people are the biggest threat to capitalist world peace. It is not in the interest of the United States to have launch ready ICBM's in North Korea under unfriendly control. Sure if Iran was Nuclear capable it wouldn't be any worse than North Korea, but the North Korean situation is not a very good one. Iran at this time is more aggressive than North Korea which I suppose makes it a more dangerous situation. It is irrelevant as to whether Iran are Nuclear capable or not as it immediately becomes concerning to the Western World when there is even a chance of new Thermo-Nuclear Warheads. At the end of the day the threat of Thermo-Nuclear war is determined by the actions of those who have the same capabilities and those who oppose the enabling of Nuclear capabilities.