Is waste heat produced by human activities important for the climate?
No. In any given period of time, the sun provides almost 10,000 times as much energy to the Earth’s surface as we emit into the environment through industry, transport, housing, agriculture and other activities, providing 8.5 quatrillion Watts (8.5*1016W). The average heat flux of a human body, about 100 Joules per second (i.e. 100 Watts) represents only a few percent of the energy flux through our power supply systems, and is thus negligible on a global scale when compared to the energy received from the sun. We are not changing the global climate directly through the heat we produce.