Our planet is a beautiful complicated system, and that’s what makes it so interesting to study! (Source)

Human-caused climate change has become an overwhelmingly agreed-upon scientific truth. Many climate scientists have become worried about the impact that we are having on the atmosphere and how that is going to negatively affect us in the future. However, naysayers continue to come up with arguments to downplay humans' true role in the recent warming of our climate. One common dispute is something along the lines of “The climate has changed in the past, so why should we be worried now?”

Temperature records over the last 140 years show a clear warming trend (Source)

This tactic can be effective, and it actually gets at a deeper question within climate science. It’s true that Earth’s climate has changed in the past. These changes have a variety of different causes. Some of them emerge from the natural chaos of the climate system, and others are imposed by outside forces. The climate system has a lot of moving parts that are difficult to disentangle. This distinction is called internal vs external variability. Much of the work that climate scientists due is devoted to separating these two factors in current trends that are being observed.

Variability is a complex topic. There are entire textbooks devoted to studying and describing change in a chaotic system. Statistics provides us with many ways to describe variability and its magnitude. This becomes an especially difficult problem with a system as large and tough to observe as Earth’s climate. In this article, I’m going to talk about the difference between internal and external variability. I’ll also talk about how climate scientists distinguish between the two and how that is applied to human-caused climate change. Let’s dive in!

Much of the climate system fluctuates due to randomness within itself (Source)

Changes From Within

You may have heard the term internal variability before. This is a fancy phrase basically just used to say that the climate system is chaotic. It will fluctuate on its own without any outside forces. This is why the weather is so hard to predict, we have a rough idea of how it will develop but its internal variability will never let us get it…

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