My generation, the millennials, will never know a time when climate change wasn’t a grave threat.
Back in 1988, carbon dioxide in the atmosphere crossed the 350 parts per million level when I was still watching Sesame Street and digging up worms in the backyard. Scientists consider that mark the maximum threshold compatible with a stable climate and suitable for human life on Earth. That same year, NASA researcher James Hansen told the U.S. Senate he was 99 percent confident global warming was already taking place. The public started taking notice, but little was done to address the accelerating crisis.
Earlier this year, scientists in Hawaii and California confirmed that our planet’s level of atmospheric CO2 had surpassed 411 ppm. It’s at the highest concentration in human history — not just over the past 100 years or so of modern recordkeeping, or since the Industrial Revolution, or since the invention of agriculture around 9000 B.C. There’s more of the planet’s main greenhouse gas in the atmosphere since before our species evolved from our distant primate cousins millions of years ago.