Sustainable Alaska: Humans vs. Volcanoes

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By Sonia Nagorski

The current concentration of carbon dioxide in Earth’s atmosphere is higher than it’s been in at least 4 million years, but it’s certainly not the highest in Earth’s 4.5 billion year history. In fact, CO2 levels were often double current levels for much of the past 500 million years. As a result, our planet has experienced substantially warmer (and cooler) temperatures than what we are feeling now.

Before humans began burning fossil fuels prodigiously, volcanic eruptions were the main source of CO2 inputs to Earth’s atmosphere. Other factors that are important in regulating Earth’s climate over time include the strength of the sun’s radiation, continental weathering,

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