How Much CO2 Is Too Much?
August 17, 2009
Being one of those analytical, left-brain, anal, dorky types, I hate it when people talk about the need to reduce greenhouse gas emissions without putting real numbers on the problem. Oh sure, there’s beginning to be some sort of wishy-washy jello-like sort of consensus on numbers like “80% reductions by 2030″ but that says very little about just how much CO2 and other greenhouse gases our battered atmosphere can take.
The number that many really smart people want us to know more about is 350. This, in climate scientists’ considered opinion, is the atmospheric concentration of CO2, in parts per million (ppm) that we need to be shooting for now if we’d like to avoid some pretty awful consequences.
Click on image for CO2 Simulation
One problem with this number is that, well, we’re at 390 ppm right now! And this concentration is growing at about 3% per year, so next year it will be about 400 ppm, and so on and so on.
So here’s the thing – and this is a thing that many many people truly don’t realize: We’re already past the danger level as far as CO2 concentration is concerned and EVEN IF WE STABILIZE CO2 EMISSIONS NOW THE CONCENTRATION WILL KEEP RISING.
There’s a good animation you can check out that does a good job of making this notion more obvious and clear. Click on the image in this post to see it. (The “danger” level that this animation uses is 450 ppm, a more politically palatable number…) For more on this animation, its designers and the science behind it, click HERE.
So why the more aggressive target of 350 ppm? This is how James Hansen puts it in his famous paper Target Atmospheric CO2: Where Should Humanity Aim? (he’s head of the NASA Goddard Institute for Space Studies and was the guy who famously warned the US Congress about climate change in 1988):
“Alpine glaciers are in near-global retreat [refs]. After a one-time added flush of fresh water, glacier demise will yield summers and autumns of frequently dry rivers, including rivers originating in the Himalayas, Andes and Rocky Mountains that now supply water to hundreds of millions of people. Present glacier retreat, and warming in the pipeline, indicate that 385 ppm CO2 is already a threat.
Equilibrium sea level rise for today’s 385 ppm CO2 is at least several meters, judging from paleoclimate history [refs]. Accelerating mass losses from Greenland [refs] and West Antarctica [refs] heighten concerns about ice sheet stability. An initial CO2 target of 350 ppm, to be reassessed as effects on ice sheet mass balance are observed, is suggested.”
Now these are just the 2 paragraphs where he sets this target of 350, but there’s a whole lot of science behind WHY this is so important. You can trust me on that, or you can read his paper. Come on, go read it. A half-hour well spent!
And then you’ll begin to understand who the crazy fools are: the tree-hugging greenies screaming about the need to DECARBONIZE our economy fast, or those business-as-usual types warning us to be cautious in our emissions goals in order to not adversely affect jobs…
Jacques LeCavalier & Associates Inc.
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That simulation really drives the message for me. From what I’ve been reading or listening to lately, the relationship between CO2 and climate change is more exponential than linear. I’m wondering how this could modify the simulation.
Thanks for the comment, Richard! You may be right that the trend is exponential rather than linear, but once we get beyond that two-degree rise in global average termperature, the experts seem to say that predictability goes out the window. Some mechanisms may then be set into motion that are quite rapid and that would make this simulation seem very gentle indeed.
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