How much does earth's core temperature affect earth's global surface temperature

Has anyone managed to read the (latest) full IPCC-report and do you know whether they have taken into account the Earth's core temperature in their models. Besides the IPCC-report, do we know how much the climate and temperature on Earth's surface is effected by it? As I'm guessing, the core temperature of the earth is an very important variable that the climate-models need to have.

• The internal heat flux is, on average, about 0.1 W/m$^2$, while the incoming solar radiation is about 340 W/m$^2$. So internal heat is not an important variable for climate models. See for example this answer: earthscience.stackexchange.com/a/431/18081 Aug 22, 2021 at 20:57
• @Jean-MariePrival It also does not change much in time, so it can be neglected in climate change calculations. I could not find an estimate of how many degrees warmer it makes the surface. Saturn is 32C warmer due to internal energy flux! Aug 22, 2021 at 21:40
• To be an important variable it needs to be shown it is varying; it is not ignored or neglected - just known to be both relatively small in total amounts of heat flow and known that the rate of heat flow hasn't been increasing. And a whole lot of valid science would have to be ignored or neglected or overturned for the causes of global warming to still be considered an unexplained mystery. Nov 17, 2021 at 21:27
• I have designed fracture stimulation treatments for 31 years and been involved in many very complex by nature jobs with data acquisition analysis from microseismic evaluation that I can say fracing has nothing to do with anything regarding heat transfer from the earths core! Every single description of fracking here is so off track it needs to be disregarded! May 4 at 17:43

It's not the earth's core temperature per se that matters, but rather the amount of heat that flows from the core to the surface. Just like holding a cup of hot coffee - if the mug is insulated, it's fine, but if it's just thin metal, then your fingers will get burnt. The flux of heat through the surface of the solid earth is less than ~0.5 W/m$$^{2}$$. The sun heats the surface of the earth at an average rate of ~200 W/m$$^{2}$$ (which varies with latitude). We can therefore conclude that the heat coming from the centre of the earth isn't a big factor for the surface temperature of the land.

This paper from 2001 discusses the impact of the geothermal heat flux on the ocean. They use an approximation of the coupling between the atmosphere

$$\frac{\partial T_{ocean}}{\partial t} = \lambda (T_{ocean} - T_{0})$$

that relaxes the ocean temperature, $$T_{ocean}$$, back towards a set temperature, $$T_{0}$$, at a rat of $$\lambda$$ W m$$^{-2}$$ K$$^{-1}$$. They use a value of 32 W m$$^{-2}$$ K$$^{-1}$$, so an extra heat flux of 0.5 W m$$^{-2}$$ leads to a change in surface temperature of $$1.5 \times 10^{-3}$$ K. Not really noticeable.

If we look at the deep ocean, 3,000 m and below, then their results suggest that this heat flux can make a small but discernible difference; in their model the deep ocean is about 0.2-0.3°C warmer because of the heat flux coming through the sea floor.

• Rather than just passing it off by relative scale, I'd think the Stefan Boltzmann Law may offer a fair thought of what small factor 0.5 $\frac{W}{m^2}$ really has, given its 4th root relationship from radiation to temperature? Aug 23, 2021 at 11:47
• This is a great answer. It's worth adding that the heat flux from core to surface is whatever it is. It doesn't lead to a heating or cooling of the atmosphere, it would simply contribute to keeping the temperature at the earth surface where it was historically. In other words, it's a constant contribution, unrelated to the climate change that the IPCC reports address. Aug 23, 2021 at 22:18
• Thank you for the answer. Then what's the heat flux from a volcano since I guess molten lava comes from the core from there? Are these volcanic things implemented into the average-computation of the total heat that flows from core to surface? Thanks. Aug 23, 2021 at 22:24
• @NaturalNumberGuy - estimates of geothermal heat flux includes heat from volcanic eruptions. Nov 17, 2021 at 21:31

This Skeptical Science article explains that geothermal is very small, $$0.09W/m^2$$, compared to radiant heat flows. It also does not change much in time, so it can be neglected in climate change calculations.

For an airless planet the equilibrium temperature $$T$$ can be calculated from $$F=\sigma T^4$$where $$F$$ is the average absorbed heat flux at the surface and $$\sigma$$ is the Stefan-Boltzmann constant. If there is an additional internal flux $$I$$, the equilibrium temperature is increased by $$\Delta$$: $$F+I=\sigma(T+\Delta)^4$$ For small $$I$$ this leads to $$\Delta \approx \frac{TI}{4F}$$ Without the atmosphere, $$I$$ is three orders of magnitude smaller than $$F$$, so $$\Delta$$ is a fraction of a degree. I don't think the atmosphere would amplify this effect.

There is no evidence of long term change to the rate of flow (flux) of Earth's internal heat to the surface; without evidence of variability it doesn't get treated as a variable. It doesn't get included in climate models because there is no evidence it is a climate forcing over the time scales for anthropogenic global warming, not because it has been overlooked.

Scientists have given consideration to every conceivable cause for climate to change, both in long term paleoclimate terms and specific to current observed warming. That includes use of temperature data from boreholes - which show warming (change) currently occurring from the surface down, diminishing as depth increases.

Climate scientists have looked at estimates and quantification of heat fluxes and evidence of underlying change, found them to be inconsequential to observed and predicted climate change.

I would like to give some food for thought here. I live in Louisiana where fracking is causing cracking deep below the surface of the earth. If you look at a map of fracking locations in the US you will be shocked at the number or amount of red dots that pinpoint fracking locations. One state is almost completely filled with red dots. There are hundreds and hundreds of thousands fracking locations from north to south part of the central US. While fracking miles below the earths surface then horizontally for over 5 miles in some cases fracking technique uses 6 explosions of like dynamite every 1’ of cutting into the rock. Yes, 6 dynamite explosions every 1’ in order to break the rock for the drill bits to drill through. Now use that calculation 6 explosions per foot along with the depths of the explosions times the number of the hundreds of thousands of fracking locations to determine how much the rock miles below ground that is closer to the earths core has been loosened. The broken and cracked rock below the earths surface that is an insulating factor that helps protect the earths surface has been broken and cracked in hundreds of thousands of locations due to fracking. The insulating rock below, the insulation, that protects the earths surface is being destroyed and weakened therefore heat from the earths core will find the path of least resistance and that my friends is through the broken and cracked rock caused by fracking miles below the earths surface.

Mixed toxic chemicals and fluids are made and concocted by non scientist that are used in fracking to cool down the fracking drill bits. It is very hot below where fracking takes place and the toxic chemicals being used may also be a contributing factor to the earths surface heating up.

• While it is true that the crust is insulating the surface from the heat of the mantle (which is why heat flux is higher where the crust is thinner, i.e. under the oceans), I don't think fracking can improve significantly the heat transfer from the Earth's interior. Heat will go through the crust by conduction anyway, regardless of the presence of faults/fractures. Moreover, most fracking is done at relatively shallow depths (< 5 km), while continental crust is 30 km thick on average. Such shallow fractures are far from reaching the mantle, thus cannot be used to transport its heat effectively. Jun 25, 2022 at 9:16
• (I'm not defending fracking, which clearly presents some environmental issues, but I don't think it can be responsible for heating the surface.) Jun 25, 2022 at 9:17