Tennesseein' is Tennebelievin'

[Title thanks to The Simpsons]

My brother-in-law Dave Willett sent me an op-ed from the Tennessean titled "Primary cause of global warming is force of gravity". Normally I hesitate to comment on science outside my expertise, but by attributing climate change to gravity, the author has brought this into my wheelhouse.

What's dangerous about this piece is that it mixes accurate information with unsupported conclusions. I thought the best way to tackle it would be a running commentary.

Climate change throughout planet earth is occurring and is observable, measurable, provable and, most importantly, unavoidable. Through numerous empirical methods the inexorable warming trend is being monitored and documented by researchers throughout the world. Thus mankind's influence on weather patterns and global warming is minuscule compared to the colossal heat-producing forces within the earth itself.

The main thing that bugs me about this passage is "thus". It suggests that the first part is in any way connected to the second, when in fact mankind's influence is painfully clear:

Wikipedia

Each line represents a different temperature-recording technique. Notice the massive uptick during the 19th and 20th centuries, strongly correlated with the advent of industrialization. This plot alone contradicts the author's thesis: Warming from the Earth's mantle would be a constant effect, with no connections to human history.

[...]
The earth itself is a heat-generating machine and is gradually warming, as is virtually every other planet, star and asteroid in our universe. The primary cause of this increase in global temperature is purely and simply the force of gravity. Due to the ubiquitous, ever-present force of gravity, our earth is gradually and inexorably shrinking. The force of gravity at the earth's surface is 9.80 m/sec/squared and increases greatly as it is measured closer and closer to the center of the earth. Gravitational pull increases the internal pressure in the earth itself and thus increases the internal temperature.

There's a lot wrong here, but one thing that's (almost) correct: The acceleration due to gravity is 9.8 meters/second^2 at the Earth's surface. Newton's Law of Gravity states

where a is the acceleration from gravity, G is Newton's constant, r is the distance to the center of mass, and M_enc is the total mass enclosed in that radius. If you plug in the radius and mass of the Earth as a whole, you will indeed get 9.8 m/s^2. However, as you descend into the Earth, not only will r get smaller, but so will M_enc. If the mass is equally distributed in a sphere, then the mass enclosed at a certain radius will be a ratio of the volumes:

where M_tot and R are the total mass and radius of the Earth, respectively. If we plug this into the equation above, we find as you descend into the Earth, the acceleration actually decreases:

This makes sense if you imagine being in the exact center of the Earth: Which way is gravity pulling you? The Earth is symmetric around you, so there can be no preferred direction, and the acceleration must be zero. It is true that the rest of the Earth is pushing in on you, creating pressure and heat, but that brings us to the next part.

The laws of thermodynamics teach us that heat is transferred by three methods: conduction, convection and radiation. Consider the colossal heat within a few thousand feet of the earth's surface and that this heat is transferred by all three phenomena, through conduction heat is transferred to the earth's surface through the tremendous dynamic circulation of the astronomical volume of molten metal and rock. Convection currents transfer heat to the earth's surface, and the radiation of the incredibly hot geological structures also raises the temperature of our environment.

Radiation of heat is an important point for climate change. Normally, heat created by the planet is radiated into space. The excess of CO2 and other greenhouse gasses, however, reflects this heat back to the surface. From here the author goes into effects of tectonic shifts, which I won't get into, because that's not my area of expertise! 

The author emphasizes the dangers of climate change, which is a great position to have, but without understanding the causes, it's impossible to arrive at a solution. As much as I mourn the decline in society's evaluation of science, worse is the misuse of science to arrive your own desired conclusion.