The planetary temperature formula contains a term representing the rate at which heat enters Earth’s “climate zone” from sources other than the Sun. Let’s look at how large those non-solar heat flows are.
For comparison, heat from sunlight is absorbed at a rate of about 240 W/m2, or 122 W = 122 petawatts = 122,000 TW, for the Earth as a whole.
- Geothermal energy: The geothermal heat flux reaching Earth’s surface is estimated to be 47±2 TW (0.09 W/m2).
- Heat released by human energy consumption: In 2022, global energy consumption by humans was 178,899 TWh. That equates to an average energy consumption rate of 20.4 TW (0.04 W/m2). It’s likely that most of this energy is eventually released into the environment as heat, though a percentage may be bound up as chemical energy in plastics. Thus, the number for energy consumption represents an upper bound on anthropogenic release of heat.
- Tidal heating: Tides heat Earth at a rate of 3.7 TW (0.0073 W/m2), of which 95% (3.5 TW or 0.0069 W/m2) is associated with ocean tides and 5% (0.2 TW or 0.0004 W/m2) is associated with Earth tides.
These values lead to an estimated value for non-solar heating of 71 TW (0.14 W/m2). This value is 0.06 percent as large as absorbed solar irradiance.
Based on recent climate data, energy currently contributes to temperature at a marginal rate of 0.300 ℃ W-1 m2. Thus, the term raises Earth’s temperature by about 0.04℃.
How fast is changing?
- Human energy consumption increased by 20,792 TWh from 2012 to 2022. That corresponds to an increase of 2.4 TW (0.005 W/m2) or 0.0015℃ over the course of a decade. This is nowhere near large enough to be a significant contributor to observed global warming.
- There is not any mechanism that would allow the geothermal energy flux or tidal heating to be changing significantly.
Even if was changing at a significant rate (and this was somehow not noticed), that could not explain observed climate changes. Such a change would show up in planetary climate data as a change in the planetary energy imbalance, , without any associated change in the measured greenhouse effect, . Yet, observations show that there has been a significant change in the greenhouse effect in recent decades.