November 20, 2014

Just how does this Sun, Earth heating thing work anyway?

How does the whole climate scene, earth's temperature changes, the Sun's radiant heat, the green house gas effect and more work anyway? Why should we care to know?

For one thing, the physics of how and why our Earth has the temperature patterns that it has are not secret. They are actually not very complicated and they are not questionable. The physics is as well understood as the force of gravity. We understand, at our space agencies, gravity well enough that a small space craft could be launched ten years ago to meet up with a comet and go into orbit around it and even get a small lander onto that comet. The physics of our planet's temperature and the way our oceans and lands and atmosphere interact with the Sun's irradiant light are well understood from theoretical models as well as real observations to confirm that theory using satellite data. 

One of the best and complete explanations of how this works is found in the link below at NASA's Earth Observatory website. The illustrations are excellent, and anyone can feel the logic, the reality and the science reading all about it. Basically, it works likes like this: 

Visible light from the sun delivers a specific and known energy to every square meter (or square foot) of the outer edge of the atmosphere. Some energy is reflected by the atmosphere, and some adsorbed by the atmosphere and the land surface and the ocean surfaces. All these components, atmosphere, land, sea (but especially land) will soak up this light energy, become warm, and irradiate infra-red light (heat). Some of this infra-red light (heat, like you feel with your hand near a stove) can escape back into space, some does not escape but gets adsorbed by "green house gasses" such as CO2 (carbon dioxide). This warms the atmosphere, and some of this warmth is irradiated back into the ground and oceans. The amount of energy adsorbed by the land, oceans and atmosphere are not just theories, they are actually measured for real, by Earth observation satellites with instrumentation to map all of these energy transfers and balances over the entire Earth's surface. You can see the imaging data with your own eyes at the Nasa Earth Observatory link below. These are not guesses or opinions, they are physical measurements. 

So just like a pot on your stove, you are putting heat in (stove like the Sun) and some heat radiates out of the pot. When the heat leaving the pot matches the heat going in at the same rate, the temperature becomes constant at this balance of heat-in versus heat-out. Thus, as we boost the CO2 in our atmosphere we decrease the heat escaping back into space, so the Earth becomes a bit warmer. As materials heat up they will start to irradiate heat faster, so at some point the Earth settles in to a new warmer temperature as our green house gasses increase. 

Some of the same political forces that used to try to plant skepticism that smoking was bad for your health, are trying the same tactic with climate warming. But, such skepticism in the form of advertising is irrelevant because we know how much extra CO2 is added by mankind's industrial activity. Its been easy to plot, graph and measure, even measure with satellite instrumentation. 

Is most of the CO2 in the atmosphere from industry? No. But that does not matter, because we just need to increase the CO2 by a fraction of a percent to change the average temperature. A tiny percentage of our atmosphere (about 1%) is greenhouse gasses like CO2, but that 1% keeps our Earth warm enough to support life as we know it. If the tiny amount of CO2 we have now were removed, the United States would become an arctic climate as the average Earth temperature would become below freezing (minus -18 °C , or minus -0.4 ° F). Our Earth is over 50 degrees (F) warmer than Zero F, because of this tiny 1% of atmospheric gasses that adsorb infra-red heat radiated by the land and oceans. We only need to add 0.1% more CO2 to shift the average Earth temperature by a couple of degrees, and those degrees result in big effects.

I highly recommend reading the educational material below in "Earth's Energy Budget", for your personal understanding and teaching it to your friends or students. All the physics at play are well explained and the illustrations are excellent. 

As always, be your own scientist..

Sincerely Ken Mitton

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