I think that it can safely be stated that an active volcano is generally regarded as one of your hotter environments. Even so the amount of heat that a volcano puts into the atmosphere is miniscule compared to the heat output of a developed nation such as America.

Robert Wright and Luke Flynn from the University of Hawaii in Honolulu are very interested in this topic and used a NASA satellite to measure the heat emitted by the world's 45 most active volcanoes, which are responsible for the majority of the Earth's volcanic heat. Over a 2 year period these volcanos put out enough energy to power New York for 2-3 months. Compared with the active volcanos it is estimated that America emits 1,000 times the energy into the atmosphere.

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