(Cross-posted from The Paragraph.)Today’s global warming is unique among the Earth’s warm periods. The rise in average world-wide temperature (0.7°C over the past 100 years) is much faster-paced than the warming after an ice age (4 – 7°C over 5000 years).⁹⁰ And the rise of carbon dioxide (CO2) in the atmosphere (80 parts per million (ppm) — up 27% — over the past 100 years) is much, much faster-paced than the rise of CO2 after an ice age (about 80 ppm in 5000 years). Since CO2 is the main greenhouse gas, and since there has not been much rise in solar radiation over the past 100 years, we are left with the greenhouse effect as the only explanation for today’s warming.⁹¹⁹² Scientific models show that the greenhouse effect has indeed caused today’s warming.⁹³⁹⁴ And data shows that the burning of fossil fuel has mainly caused the rise in CO2, giving another unique feature to today’s warm period: it is caused by the activity of an animal species — the human.⁹⁵

For comparison, here is a look back at other warm periods:⁹⁶

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