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Carbon Cycles
Let’s start with the “Greenhouse Effect”. With any class of students, a simple box with a plastic wrap and a thermometer, you can show that light entering the box is absorbed and converted to heat, and the heat can’t get out through the plastic wrap as well as the light got in. This is the same method that allows people to extend the growing season for their crops in a large-scale greenhouse. It is why homes can be designed so that the low-angled light of winter can bypass a lattice structure to allow free solar heating, while the same lattice blocks the summer sun, which peaks at a higher angle. This is why your car overheats in the summer sun, and how it can be deadly for pets or children when the adult forgets this science lesson. This is not scientifically or politically controversial. The greenhouse effect is real, and if there are “greenhouse skeptics”, you could prove it to them with some simple experiments. * https://phet.colorado.edu/en/simulations/greenhouse-effect
Then we can move to some planetary atmospheric lessons. Our Moon has a weaker gravitational pull at the surface than the Earth, as does Mars, so their atmosphere is thinner. There is a dual purpose for spacesuits on both Mars and the Moon: to provide breathable air, and to keep the temperature regulated. For Apollo astronauts on the Moon, there was a temperature difference of over 400°F (232°C) between shade and sun. On Earth, the gases in the atmosphere absorb much of the electromagnetic spectrum of the sun’s rays, protecting us from UV- and X-rays that would be dangerous, while allowing most of the light from the sun to get through. Images from satellites can show how the universe looks across the electromagnetic spectrum, and how it looks to us after it passes through the atmosphere. There are also interesting simulations online showing how light passes through some gases unaffected, while infrared rays (say, from a heat lamp) are absorbed and scattered about. This is how the Earth’s atmosphere acts as a greenhouse, and protects life on Earth, both by trapping heat (so we don’t freeze at night) and by scattering UV-and X-rays (so our cells aren’t damaged, leading to cancer or organ failure). Again, none of this is scientifically or politically charged, and what classroom doesn’t benefit from lessons that talk about outer space? * https://phet.colorado.edu/en/simulations/molecules-and-light
Next up is some basic chemistry. What we call “natural gas” is a molecule with one carbon atom bonded to four hydrogen atoms; gasoline is a larger molecule with eight or so carbon atoms bonded to hydrogen. When we combine it with oxygen and give it a spark to separate the chemical bonds, the oxygen atoms combine with the hydrogen atoms to make water vapor, and the carbon atom combines with oxygen to make carbon dioxide, the same gas that keeps the heat on Earth from passing straight out into space. This is a more abstract lesson, since it involves atoms too small to see, but a molecular modeling kit can help, and the same reactions happen when a candle burns, so the presence of water and carbon dioxide can be shown experimentally. Again, there is no scientific or political controversy about this part of the lesson. * https://www.youtube.com/watch?v=9tkDK2mZlOo
Now we get into some more challenging material, but it is based upon the uncontroversial carbon cycle. The atmosphere is a mixture of many different gases, but it is the oxygen molecule that animals need to breathe in, and the carbon dioxide molecule is the one they need to breathe out. Plants, on the other hand, absorb the carbon dioxide and use the carbon to build their fibers, “breathing” out the extra oxygen. It is a beautiful cycle of life, and without a shred of scientific or political controversy. This balance has been maintained for millennia, with humans gaining carbon compounds (like sugar and starch) from plants, and exhaling the carbon dioxide that can go into the crops of the next season. We can show that carbon dioxide levels in the atmosphere go down during the growing season (because the plants are using the carbon atoms to grow) and go up during the fall (because the plants are dying and decaying). * https://www.youtube.com/watch?v=xtyieNg18O0
The climate change issue arises when we combine the idea that a natural growing/decaying cycle has been supplemented by the combustion of fossil fuels. The carbon atoms that make up these fossil fuels have been buried in the Earth for millenia, and we are now adding them to the atmosphere in the form of carbon dioxide. This fact, again, is beyond any scientific controversy. The controversy begins when we examine these hypotheses: that the carbon dioxide we are adding to the atmosphere cannot be absorbed quickly enough by plants, so the carbon dioxide levels will rise significantly, and that this excess carbon dioxide will trap enough heat to change the Earth’s climate.
In order to test this hypothesis, there needed to be a reliable way to measure the carbon dioxide in the Earth’s atmosphere, and to compare it to levels in pre-industrial eras, when fossil fuel consumption was unknown. Many decades of research has refined our measurements of carbon dioxide in the atmosphere, and ice core samples have allowed us to determine the levels of carbon dioxide in the atmosphere in the preindustrial era. Although it has taken time and diligent efforts to create this data, there is a near-universal consensus that the current levels of carbon dioxide in the atmosphere are unprecedented. I have not seen any “climate change skeptics” who question these findings. * https://climatedata.imf.org/pages/climatechange-data
The questions arise when we try to match carbon dioxide levels with planetary temperatures. It is hard to take the temperature of a planet. Because of the tilt of the Earth, half will experience winter, while the other experiences summer. Because of wind patterns, some areas will be hotter in the summer than others, and some will be colder in the winter than others. Still, after refining methods of measurements and averaging, it is a near-universal consensus that the planet is warming. Cold days in some places do not challenge this conclusion, since a planet’s temperature has to be averaged over time and space. When someone claims that the latest snowstorm disproves the climate change hypothesis, they are simply misunderstanding (or obscuring) the issue. The conclusion that the Earth is warming and the ice caps are shrinking is not a controversial claim.
