Climate 411

This is the final installment of a five-part series by Bill Chameides on How We Know Humans Cause Global Warming.

1. A 175-year-old Puzzle
2. What Chemistry Tells Us
3. Causes of Past Climate Change
4. The Medieval Warming Period
5. The Only Explanation Left

Compared to 100 years ago, the temperature of the atmosphere is warmer. No one disputes that. And no one disputes that an extra source of heat must be causing it – that’s a basic law of physics. But how do we know that the source of the heat is increasing levels of greenhouse gases from burning fossil fuels and deforestation?

So far in this series I’ve described how the relationship between atmospheric carbon dioxide (CO₂) and global warming was discovered, how carbon isotopes prove that rising CO₂ concentrations are from the burning of fossil fuels, and how the orbital shifts that cause ice ages cannot explain our recent warming.

That certainly suggests that global warming is caused by increased CO₂ from burning fossil fuels, but how can we be sure?

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This is the fourth installment of a five-part series by Bill Chameides on How We Know Humans Cause Global Warming.

1. A 175-year-old Puzzle
2. What Chemistry Tells Us
3. Causes of Past Climate Change
4. The Medieval Warming Period
5. The Only Explanation Left

In my previous article in this series, I talked about climate change patterns over geologic time. I showed how today’s spike in temperature and carbon dioxide (CO₂) concentration breaks patterns and records going back 600,000 years.

This departure can be seen even more clearly when you look at just the last 1000 years (see graph in previous post). So what is this you hear about a Medieval Warming Period?

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This is the third installment of a five-part series by Bill Chameides on How We Know Humans Cause Global Warming.

1. A 175-year-old Puzzle
2. What Chemistry Tells Us
3. Causes of Past Climate Change
4. The Medieval Warming Period
5. The Only Explanation Left

An argument I hear frequently from climate change skeptics goes like this: "Climate has undergone warming and cooling cycles for millennia. This is no different. It’s just another naturally occurring warm cycle."

It’s true that climate has undergone warming and cooling cycles for millennia, but it’s not true that this is just another naturally occurring warm cycle. Here’s why.

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This is the second installment of a five-part series by Bill Chameides on How We Know Humans Cause Global Warming.

1. A 175-year-old Puzzle
2. What Chemistry Tells Us
3. Causes of Past Climate Change
4. The Medieval Warming Period
5. The Only Explanation Left

There’s no question that carbon dioxide (CO₂) is a greenhouse gas that warms the planet, and that CO₂ has been increasing. The graph below shows it vividly (the measurements were taken at Mauna Loa, Hawaii).

But how do we know that the increase is due to people burning fossil fuels? One way is by analyzing the chemistry of our atmosphere, since human activities leave an unmistakable "fingerprint".

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