Claim: “Temperatures have been much higher in the past, especially if you go back millions of years.”
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True, but not much comfort. Some even go back as far as 485 million years, seemingly unaware that back then Earth’s land was barren rock and life was confined to the sea.
Humans have only existed for about 300,000 years, and all of civilisation, including farming, cities and stable coastlines, developed in a narrow, stable climate over the last 10,000 years or so. It’s not Earth that’s at risk from a hotter climate. It’s us, and all the nature that has adapted to today’s climate.
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Those hot periods were driven by CO₂. Over the past 485 million years, global temperatures have ranged from about 11°C to 36°C, compared with about 14°C before industrialisation. The same research found that carbon dioxide was the main driver throughout. When CO₂ was high, the planet was a hothouse. That’s a warning about what high CO₂ does, not reassurance.
Our civilisation grew up in a narrow band. Farming, cities and coastlines all developed with CO₂ at around 280 parts per million. We’ve pushed it above 420 ppm in under two centuries, a level not seen in millions of years.
Speed is the problem. Past natural changes typically unfolded over thousands or millions of years, giving species time to adapt or migrate. Even so, some caused mass extinctions. Today’s change is happening far faster than almost any natural change in Earth’s history.
The question isn’t whether Earth will survive. It will. The question is whether the food systems, cities, societies and natural world we depend on can cope with a change this fast.
