According to an announcement from the National Oceanic and Atmospheric Administration (NOAA), a remote South Pole observatory passed a scary milestone in May.
The Antarctic station registered an average concentration of 400 carbon dioxide parts per million in the atmosphere, making it the last station on Earth to finally pass that critical threshold. As Julian Huguet explains in today's DNews report, the number suggests that elevated carbon dioxide levels have now thoroughly spread across the entirety of the planet's atmosphere.
That can't be good, right? Right: Planet Earth has not seen CO2 levels like these at the South Pole in four million years. But climate change deniers might read that factoid a little differently. If we had elevated levels like this millions of years ago, and everything turned out OK, then no need to worry, right?
Wrong: The critical difference between now and then is that CO2 concentrations are ramping up with deadly speed in the last few decades. When carbon dioxide levels peaked in epochs past, it took thousands of years for those levels to gradually rise. Back then, the biggest emitters of CO2 were volcanic explosions.
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Since the Industrial Revolution, we're measuring these spikes in tens of years instead of thousands of years. Over longer periods, rising CO2 levels -- and accompanying global temperature changes -- aren't as immediately dangerous. Organisms can change and adapt, and indeed few species went extinct during these historical periods.
Scientists who are watching our current climate change models are not so optimistic. With temperatures rising sharply and quickly, many organisms likely will not be able to survive. There's also the matter of the comedown. Even if humanity were to become net carbon neutral today, the natural processes that bring CO2 levels back down operate on a geologic time scale. The last major drop took around 150,000 years.
So while it's true that CO2 concentrations have been higher than they are now at various points in Earth's history, it's a dangerous soundbite to circulate out of context. That doesn't stop climate change deniers from circulating it anyway, so heads up.
-- Glenn McDonald
Live Science: Dinosaur Era Had 5 Times Today's CO2
Climate Central: Antarctic CO2 Hit 400ppm For First Time In 4 Million Years