Scientists studying Antarctic ice cores that include more than 650,000 years of past climate history have never found CO2 levels even close to those of the present ones. Pre-Industrial Revolution levels, i.e., before the extensive burning of fossil fuels, were at 275 ppm, far below the current level of 387 ppm.
The CO2 level recorded prior to industrial fossil-fuel burning is that which trapped enough heat to maintain global temperatures to which life on Earth adapted. At the current elevated level of heat-trapping CO2, the Earth is showing signs of a planetary "fever".
Arctic sea is melting, sea levels are rising, and climate patterns around the globe are changing. Glaciers, the source of drinking water for hundreds of millions of people, are melting and disappearing. Disease-carrying mosquitoes that thrive in a warmer world are spreading to new places including south Texas. Drought is becoming more common, making food crops harder to grow in many regions.
Environmentalist and author, Bill McKibben, thinks that 350 is the most important number on Earth. In fact, he founded an international movement called simply 350, aiming to inform people around the world that 350 ppm is the level scientists have identified as the safe upper limit for CO2 in our atmosphere. Hopefully, this will help move international climate negotiations closer to science than they’ve been in the past.
McKibben aims to create a world-wide grassroots movement connected by the internet and to hold decision-makers accountable to producing a climate treaty that is strong, equitable, and grounded in the latest science, the science of 350. On October 24, 350.org is holding a Global Day of Climate Action to do just this. “We hope it represents a climactic moment in the climate movement to show that people around the world are watching the outcome in Copenhagen,” says May Boeve, an international 350 coordinator. “We need a strong treaty to get us to a safe level. We are ultimately building toward that point.”
So how do we reduce the CO2 level below 350?
- No more new coal plants, because although the world still has immense amounts of coal, it's immensely dirty.
- A cap on the amount of carbon the country can produce, with permits paid for by the upstream producer who mines, imports, or sells the fossil fuel .
- An international agreement, including China and India, to do the same thing around the world.
This weekend there were two conferences focused on that single number, 350. "Getting to 350" was held at Middlebury College in Vermont, and "The 350 Climate Conference" was held at Columbia University in New York. James Hansen spoke at Columbia and via video conference at Middlebury. Bill McKibben spoke at Middlebury via video conference from the other side of the planet in New Zealand, where he is spreading the word about the most important number on Earth.