Are high CO2 levels harmless because they also occurred in the past?

While the Earth adapted to high carbon dioxide levels in the past, modern civilization cannot without major consequences.

Past periods of high CO2 brought about a climate vastly different from our own. During the Eocene “hothouse” period around 55 million years ago, CO2 concentrations peaked at 1,600 parts per million. That epoch saw ice-free poles and palm trees above the arctic circle.

The last time CO2 was as high as today was 3 million years ago. Global temperatures were as much as 7°F (4°C) warmer and sea levels were as much as 80 feet (25 meters) higher.

Given that 40% of the population lives around 60 miles (100 kilometers) from the coast, rising sea levels from CO2 emissions threaten a global climate refugee crisis.

The rapid CO2 rise today, compared to the gradual rise historically, compounds the danger, with our food systems and ecosystems already struggling to adapt.