NASA climate scientist James Hansen predicts we need to bring CO₂ levels down to the level we had in 1990 in order to maintain a climate similar to what we have had over the last 10,000 years. What is that 1990 CO₂ level?

Question

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The CO₂ level we had in 1990 was around 350 parts per million (ppm). Hansen suggests that bringing CO₂ levels down to this level is necessary to avoid the worst impacts of climate change and maintain a stable climate similar to what we have had over the last 10,000 years.

NASA Climate Scientist James Hansen Predicts We Need to Bring