The current ice age is a geologically rare event, threatened by human activity. Emissions reduction won’t be enough to resolve climate change. Instead, we must learn from the ancient past to stabilize
In April of last year, the concentration of carbon dioxide in the Earth’s atmosphere reached 410 ppm. This is the highest in over 3 million years, and much higher than the pre-industrial average of 280 ppm. The last time CO2 levels were this high, in the middle Pliocene epoch, the average global temperature was around 3 °C greater than today, and sea levels were 25 meters higher. The time before that, in the middle Miocene, sea level was 40-50 meters higher.
Assuming “business as usual,” CO2 concentration is projected to be 600 to 800 ppm by the end of the century. Optimistic projections not involving sustained negative emissions starting at mid-century give an average of ~2°C warming by 2100. Even that is considered by authorities to be a problem, but it’s less than the paleoclimatic analog.