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Why climate change is so important, in one chart

For decades now, data have shown our carbon dioxide levels and global average temperatures marching up due to human-induced climate change. As explained in this video, one simple chart helps clarify why that matters:

It's widely recognized now that the global climate is increasingly a product of human activities. But less understood is how human activities are a product of the global climate.

The chart below shows what life was like for much of human history. Using data from ice cores, it indicates how temperatures varied over time. Notice the relatively flat line over the past 10,000 years — that's when agriculture began:

temperatures past 100,000 years

Modern humans appeared around 200,000 years ago. 188,000 years later, they started farming, independently in at least four different parts of the world. Civilization followed shortly thereafter.

Was the timing coincidental? Not likely. According to one analysis by researchers at the California Institute of Technology, it was climate change that prevented the development of agricultural societies up until around 12,000 years ago:

[W]e find that between 50,000 years ago and ... ~ 11,600 years ago there was probably no time span as long as 2,000 years that was free of relatively large century scale variations.

In other words, we got lucky. Despite plenty of regional climate variations — some of which contributed to the fall of great civilizations — temperatures and sea levels have been stable enough for agriculture to lead to society and for society to eventually lead to industrialization, science, medicine, the internet, and the device you're using to read these words. Now, with man-made global warming, we are tossing that stability away.

Some might look at this chart and conclude, "Why worry about man-made global warming when natural climate change is inevitable?" But if an ice age is coming down the road, it might not be for thousands of years. The things that matter to us operate in a much narrower time scale. Electricity dates back only 130 years.

What do we want the coming decades and centuries to be like for the 11 billion people who will inhabit the planet by 2100? That much, at least, is up to us.


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