Anthropogenic heat is a small influence on rural temperatures, and becomes more significant in dense urban areas. It is one contributor to urban heat islands. Other human-caused effects (such as changes to albedo, or loss of evaporative cooling) that might contribute to urban heat islands are not considered to be anthropogenic heat by this definition.
Anthropogenic heat is a much smaller contributor to global warming than greenhouse gases are. In 2005, anthropogenic waste heat flux globally accounted for only 1% of the energy flux created by anthropogenic greenhouse gases. The heat flux is not evenly distributed, with some regions higher than others, and significantly higher in certain urban areas. For example, global forcing from waste heat in 2005 was 0.028 W/m, but was +0.39 and +0.68 W/m for the continental United States and western Europe, respectively.
Although waste heat has been shown to have influence on regional climates, climate forcing from waste heat is not normally calculated in state-of-the-art global climate simulations. Equilibrium climate experiments show statistically significant continental-scale surface warming (0.4–0.9 °C) produced by one 2100 AHF scenario, but not by current or 2040 estimates. Simple global-scale estimates with different growth rates of anthropogenic heat that have been actualized recently show noticeable contributions to global warming, in the following centuries. For example, a 2% p.a. growth rate of waste heat resulted in a 3 degree increase as a lower limit for the year 2300. Meanwhile, this has been confirmed by more refined model calculations.
A 2008 scientific paper showed that if anthropogenic heat emissions continue to rise at the current rate, they will become a source of warming as strong as GHG emissions in the 21st century.