You might have heard of the term “Milankovitch Cycles”. These are some of the most powerful forces in determining Earth’s climate.
The Three Milankovitch Cycles
Eccentricity is the most influential cycle for our climate. That is just how circular/elliptical the Earth’s orbit around that sun is. Over the course of 100,000 years, it cycles between circular (how it is now) to elliptical.
The next is called obliquity. This is earth’s tilt. It swings between 22.1 and 24.5 over a period of 41000 years. Currently, it is pretty much in the middle.
Finally we have precession. This one was hard for me to understand at first, but it’s pretty much how much Earth wobbles around it’s axis. It changes the timings of the seasons slightly. The phrase “precession of the equinoxes” is in reference to this. This cycle takes is 26000 years to complete. It goes between “Perihelion”, where the Northern Hemisphere’s Summer solstice occurs when Earth is closest to the sun, and “Aperhelion” when the Summer solstice is furthest from the sun.
Milankovitch Cycles On Our Climate
So what does this have to do with climate?
Each extreme end of these cycles makes our climate warmer or cooler. Sometimes these align and cause an ice age or interglacial period (what we’re in now).
| Milankovitch Cycle | Cold | Hot |
| Eccentricity | High eccentricity | Low eccentricity |
| Obliquity | High obliquity | Low obliquity |
| Precession | Aperihelion | Perihelion |
Eccentricity is by far the most influential Our almost circular journey around the sun keeps out climate fairly stable, our middle ground obliquity also contributes to our temperate climate. The Precession is not so influential, but it can contribute to the effects of the other cycles.
What Does This Mean For Us?
So where are we headed? These cycles happen over thousands of years, and a big change from these would not occur in a single life time, so it is nothing to worry about really. What IS concerning, is that according to the Milankovitch cycles, we are supposed to be heading towards cooling (very, very slowly). By this I mean a barely observable amount of cooling.
Not that it matters at all a human scale what the Milankovitch cycles are doing, and there is nothing we can do about it either since nothing short of a catastrophic meteor strike could alter the course of the Earth’s orbit (that would definitely cause the death of at least most of life on earth). But it is important to understand because one of the arguments against anthropic climate change that I hear is: “but it’s just a natural cycle”.
Yes, the Earth goes through cycles of being hot and cold to varying degrees. However, we are seeing a rate of warming never seen before in Earths history. And the natural cycles of Earth’s climate have nothing to do with it. In fact we are going the opposite direction to the natural cycles. Very quickly.
The Milankovitch cycles are interesting sources of information telling us based on how many years ago we might be investigating, we can pretty reliably estimate the global climate. Of course this would need to be confirmed with various sources of data like oxygen isotopes and the like for anomalies like if there happened to be large amounts of carbon in the atmosphere keeping the earth warmer than expected.
The Next Ice Age
Using the Milankovitch cycles, we can also predict what the climate will be like in the future. Since the cycles happen over a particular time frame, we can calculate when they will align to create the best conditions for the next ice age. This is predicted to be in about 10,000 years. But let me emphasise, in 10,000 years, the Milankovitch cycles will align for optimal ice age conditions. Not, there will be an ice age in 10,000 years.
We have pumped so much CO2 and other green house gasses, and we aren’t doing a super great job of slowing that down. There is a good chance that we will delay the onset of the next ice age by thousands of years. This is particularly hard to predict because we do not know what governments and businesses will do in the future regarding climate change. The have been many goals set and very few followed through on in terms of emission reduction.
Key Take Aways:
- The Milankovitch cycles are a collection of three cycles
- Eccentricity is the cycle of the Earth’s orbit going from circular to elliptical
- Obliquity is the cycle of Earth’s tilt going from 22.1 to 24.5 degrees
- Precession is the timing of the seasons.
- The Milankovitch cycles control Earth’s climate
- They have nothing to do with Earth’s current warming trend, and the Milankovitch cycles are (very, very) slowly (like over hundreds of thousands of years) moving towards making Earth colder
- They will align for the coldest conditions in the next 10,000 years
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