Recently, Tim sent me an email with this subject line:
Significant climate tipping points have been passed.
I opened the email to find an article about the most recent “comments and projections” by James Hansen. Hansen, you may know, is perhaps the most famous NASA climate change scientist. He’s the man who testified before Congress twenty years ago that the planet was warming and that people were the source of that warming. He’s the man who was pressured by senior officials at NASA, at the behest of the current administration, to tone down his reports about the impacts of climate change. Thankfully he seems to have resisted that pressure.
I read the article and then I read a related article by Bill McKibben. Hansen says, and McKibben underscores, that there is a critical maximum number of parts per million of carbon dioxide in the atmosphere to heed to prevent climatic catastrophe. That number, he says, is between 300 and 350.
In earlier years of climate change awareness experts were shooting for limits of 450 to 550 ppm, with the hope that those were realistic limits we could manage. But now Hansen is saying the number is much lower, between 300 and 350, if we want to avert catastrophe. Things are melting and weather patterns are changing much faster than anyone has predicted. So we need to get even more serious about reducing the carbon in our atmosphere. Three hundred fifty is the number, the number everyone should know, says McKibben in the Washington Post. While nothing is sure, McKibben says, “at least we are honing in on the right number.”
So, now, we are looking at the right number. That’s good. We’re on the right track. Can you guess how many ppm of CO2 are in the atmosphere now? Slightly below 350? Slightly above?
We’re at 383 parts per million and counting, well past the number Hansen suggests is critical. We are past it by a lot. We were at 325 parts per million in 1970! Um, I don’t think we can just suck all that carbon back out, ask billions of people not to have been born, tear down all of those new suburban developments, return to non-fossil-based agriculture, and innocently pretend it’s thirty years ago.
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