Daniels Family Sustainable Energy Foundation
WHY CURRENT GLOBAL HEATING IS NOT A "NATURAL" CYCLE
Here we explain what Milankovitch cycles are, and how greenhouse gases disrupted them
If you're on social media and you've ever looked up weather or climate, chances are that your apps are feeding you new viral videos with Neil DeGrasse Tyson interviewing astrophysicist Steve Soter. The scientists want to explain what causes ice ages, and at the same time, debunk common myths about the opposite phenomenon—global heating—which usually sound like "the sun is just burning hotter," or "we are in a natural cycle where the Earth is closer to the sun, and that's why temperatures are higher." The scientists go on to explain how these myths are wrong, even if they sound like they're based in scientific evidence. Here we'll save you 20 minutes and explain.
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As we all learn in elementary school, the Earth moves through space. It spins on itself (creating daytime and nighttime), it's tilted (responsible for seasonal changes), and it orbits around the sun, which takes 365 days, or a year. When we say "orbit" we imagine a path through space, shaped like a circle. Except the Earth's path around the sun is not exactly like a circle, but slightly oval, because the other planets' gravity pull at the Earth and move it slightly out of the perfect circle it wants to follow around the sun (known as "eccentricity").​
The changes to the orbit—making it more or less oval—mean that every 100,000 years we have a significant change in temperature, usually creating an ice age. The changes to the Earth's tilt and precession complicate this further, but the bottom line is this: the last ice age ended 20,000 years ago. We are currently between ice ages, and we're actually seeing the sun's activity declining (solar irradiance dropping in yellow in the graph).
So why is it getting hotter instead of cooler? The answer, as you probably guessed—and as Neil DeGrasse Tyson and Steve Soter explain—is the greenhouse effect. What is that? The greenhouse effect is what happens when gases like carbon dioxide and methane accumulate in the atmosphere.
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Schematic representation of the greenhouse effect. Source: Eddie Brinkman, Betase.
Sunlight arrives as a wave to the surface of the Earth, heats it up, and then the heat tries to leave the Earth in the form of infrared light (which we can't see, but can feel, just try to put your hand on hot pavement). Unfortunately, carbon dioxide and methane (among other gases) absorb infrared light, and then release it back to Earth as heat, essentially working like a blanket. If these gases were less present (if we had no blanket) the heat would escape to space, but because the blanket is there, it reflects heat back to us, just like a comforter prevents your body's heat from escaping your bed. That is the greenhouse effect. Here is a good explainer if you want to dive into the science.​
If there were no civilization, there would be a minimal, natural greenhouse effect caused by natural processes like plants breathing, the decomposition of leaves, wildfires and other natural activities that burn things naturally. Every time something burns, carbon dioxide is created.
In the last 2000 years, and especially the last 200 years, humans have burned a lot of fossil fuels—increasing carbon dioxide in the atmosphere—and produced a lot of methane through industrialized agriculture and animal farming. Methane is over 80 times more effective than carbon dioxide at warming the planet.
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The result is that we're warming the planet much faster, and instead of being in cooling phase (according to the Milankovitch cycles), due to the sun's activity declining, we're warming more and more every year, to levels that scientists say, have not been seen for millions of years.
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That is why we cannot simply think global heating is all just a "natural cycle." Increased heat threatens the health of the most vulnerable among us, children, the elderly and those who can't find ways to cool down because of where they live or the cost of energy.
Cooling with smart building materials, without the use of additional energy, is the key solution for the future.