The Inconvenient Skeptic: The Comprehensive Guide to the Earth's Climate

by John Kehr

With the idea in mind that the Earth's climate will change, it is time to focus on the Earth as it is now. The main focus will primarily be on the last 135,000 years. This will cover two interglacials and one glacial period. Earlier I mentioned that the Earth has longer cycles besides the daily and the yearly ones. That 135,000 year period is the minimum amount of time needed to cover one of the longer cycles that I discussed earlier. I am going to call the longer cycle of the Earth the Climate Cycle. The climate cycle has seasons just like the yearly cycle does. The hardest part to understanding the climate cycle is simply the time scale that it takes for a cycle to happen. The yearly cycle lasts 365.25 days, or 365.25 times longer than the daily cycle. The last climate cycle lasted about 120,000 times longer than the yearly cycle. Thinking of natural cycles that take this long is a challenge, but that is how the Earth has been behaving for the past million years or so. The climate cycle does contain more noise than the yearly cycle, but the similarity between the two cycles is obvious. In the yearly cycle, each point is a single month. In the climate cycle each point is 1,000 years. They are two different cycles operating on very different time scales. It is clear that the Earth has just recently (~15,000 years ago) experienced it's 8th significant warming period in the past 720,000 years (34). Instead of summer in the climate cycle, there is an interglacial. Instead of ...

CLIMATE CYCLES Roughly 150,000 years in length.