Atmospheric CO2 at highest levels in 3 million years

The level of heat-trapping carbon in the atmosphere has passed the dangerous 400 part per million (ppm) global warming milestone.

Even though this is just an “odometer reading” event — like when your car goes from 99,999 miles to 100,000 — this global warming milestone is a big number and a big deal.  The earth has not seen levels like this in at least three million years.

The news: We just crossed 400 ppm atmospheric carbon dioxide

First the news from the New York Times (my emphasis and paragraphing):

The level of the most important heat-trapping gas in the atmosphere, carbon dioxide, has passed a long-feared milestone, scientists reported Friday, reaching a concentration not seen on the earth for millions of years.

Scientific instruments showed that the gas had reached an average daily level above 400 parts per million — just an odometer moment in one sense, but also a sobering reminder that decades of efforts to bring human-produced emissions under control are faltering. The best available evidence suggests the amount of the gas in the air has not been this high for at least three million years, before humans evolved, and scientists believe the rise portends large changes in the climate and the level of the sea. …

Carbon dioxide above 400 parts per million was first seen in the Arctic last year, and had also spiked above that level in hourly readings at Mauna Loa. But the average reading for an entire day surpassed that level at Mauna Loa for the first time in the 24 hours that ended at 8 p.m. Eastern Daylight Time on Thursday. …

Carbon dioxide rises and falls on a seasonal cycle, and the level will dip below 400 this summer as leaf growth in the Northern Hemisphere pulls about 10 billion tons of carbon out of the air. But experts say that will be a brief reprieve — the moment is approaching when no measurement of the ambient air anywhere on earth, in any season, will produce a reading below 400.

Here’s what that looks like starting from 1960 — this is the famous (to scientists) Keeling curve, in a snapshot taken just last month:


Ralph Keeling, in fact, is quoted in the Times article: “It means we are quickly losing the possibility of keeping the climate below what people thought were possibly tolerable thresholds.”

Do David Koch (or Barack Obama) care? Not so you’d notice. But maybe they’ll care later, after it’s too late.

The historical context

Here’s a taste of the context for this news, since the meaning of “400 ppm” is probably not immediately apparent. (I’m preparing a larger piece on the correlation between the gigatons of carbon (GtC) we’ve been emitting, the resultant concentration of CO2 (ppm), and historical temperature increases since 1800. All three measurements are used, and it can get confusing.)

According to the lastest IPCC Assessment Report (2007), pre-industrial (pre-1800) levels of atmospheric carbon were 280 ppm. The 2005 measurement was 380 ppm. “Today” we’re at 400 ppm according to the news above. In addition, the increase is accelerating — meaning the rate of growth is growing. Before 1995, the increase was about 1.4 ppm/yr. Now it’s about 1.9 ppm/yr.

The IPCC estimates that we’ll see 450 ppm in 2030, so that average growth rate of 1.9 ppm/yr is going to increase as well. And I’ll bet they’re way low, since these days the scientists are consistently way low. (Doubt me? Even the scientists admit that. Download the Copenhagen Diagnosis (pdf), an executive summary that updates the science from 2007 to 2009, and search for the phrase “faster than”.)

350 ppm is the maximum safe number

For comparison, 350 ppm is the highest level that James Hansen says (pdf) we can tolerate if we want to “preserve a planet similar to that on which civilization developed and to which life on Earth is adapted.” More Hansen (my emphasis):

If humanity wishes to preserve a planet similar to that on which civilization developed and to which life on Earth is adapted, paleoclimate evidence and ongoing climate change suggest that CO2 will need to be reduced from its current 385 ppm to at most 350 ppm, but likely less than that….

Decreasing CO2 was the main cause of a cooling trend that began 50 million years ago, the planet being nearly ice-free until CO2 fell to 450 ± 100 ppm; barring prompt policy changes, that critical level will be passed, in the opposite direction, within decades.

Here’s what that all looks like in a handy data table:

Year Atmos. Carbon Est. Warming In Pipeline?
1800 280 ppm 0°C
“Max safe” 350 ppm
2005 380 ppm 0.8°C
2013 400 ppm 0.9°C 1.5°–2°C
2030 450 ppm 2°C (maybe) 3.5°–4°C (maybe)

There are uncertainties here, and they don’t necessarily benefit us. First, note in Hansen’s quote above the figure “450 ± 100 ppm.” That’s a lot of plus or minus, and it could go either way. Second, in the third column (“Est. Warming”) of the table, the 2°C warming associated with 450 ppm is widely taken as a given, but as argues here, it shouldn’t be. There’s no guarantee that we’ll get only 2°C at 450 ppm. It could easily be worse.

And finally, it’s admitted everywhere that the carbon-temperature effect works both ways — each affects the other. From pdf p. 49 of the Copenhagen Diagnosis:

In climate history, didn’t CO2 change in response to temperature, rather than the other way round?
It works both ways: CO2 changes affect temperature due to the greenhouse effect, while temperature changes affect CO2 concentrations due to the carbon cycle response. This is what scientists call a feedback loop.

With that in mind, look again at that “in the pipeline” column. Most scientists agree that we’ll see warming of 1.5°C (a little under 3°F) regardless. Even if we stopped carbonizing the air completely today, we couldn’t stop that amount of warming. Some are now saying we’re beyond the 1.5°C point, and that 2°C (about 3.5°F) is now inevitable. That’s the range of current opinion, and that’s what the table expresses.

Me, I’m personally more pessimistic, since in the last 10 years, every prediction has been exceeded to the fast side. We’ve been consistently wrong to the slow side, and that needs to be taken into account (click to see my personal climate model).

So what happens when 450 ppm is indeed a fact? Do we get “just” 2°C warming (about 3.5°F) on the ground, or something worse? And at that point, what’s in the pipeline, unavoidable? Remember, as we noted here, according to the same James Hansen, 3°C forces a mass-extinction scenario, or as he said in the New York Times, “game over for the climate.”

For comparison, I think 3°C is a foregone conclusion (an “in the pipeline” number) in the next 5–10 years at the earliest unless we force our “leaders” to stop. A narrow window, but still, a window.

The good news

The good news — and there is good news — is that even the most pessimistic estimates say it’s not over yet. But we do have to move on this, and now. Time for a little action in the streets, and some civil disobedience? Chris Hayes for one says yes.


To follow or send links: @Gaius_Publius

Gaius Publius is a professional writer living on the West Coast of the United States.

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  • Drew2u

    Methane, another contributor via melting permafrost, turns to diamond
    dust at high temperature/pressure. Any way of using that technology at
    well, on a grand scale?

  • Drew2u

    That was the talking point some grandpa spewed, ironically, at a fossil site I visited that predated the ice ages.

  • My bet is on the cockroach!

  • Bill_Perdue

    I had hoped I wouldn’t live to see this.

  • “libertarian” GAAAAAAAAAAAAAAA! whew, almost as bad as religionists. :-)

  • Our mid-spring CA garden this year is blooming like July.

  • I don’t think that’s a sufficient answer. I mean, not all of these “sceptics” are Jesus freaks. At least one or two of the conservatives I’ve known, equally contemptuous of anything smacking of environmentalism, are of a different sort: young people in the high-tech field who have no use whatever for religion and who usually describe themselves as “libertarian” if asked.

  • My sense of it is that our tinkering with the ‘natural’ cycles and very genetic constructs

    of nature over the past century will cause a catastrophic and rapid decline once the tipping point unfolds.

  • Lets ask the Neanderthal, who existed for nearly 250,000 years before climate events destroyed the last of them.

  • “The closest I’ve ever seen to an answer is” It makes sense to me. These people believe in a magical bad tempered sky God man, who is simultaneously all loving. Others believe in virgin birth and insemination by a holy ghost. The list goes on. Meanwhile they yearn for Rapture and the death cult, while making sure it actually happens.

  • Dave of the Jungle

    Your overwhelming consensus news for today:

  • pappyvet

    Climatologist James Hansen of the NASA Goddard feels that we may have already gone beyond the tipping point. If thats the case,Mother Earth may be getting ready to spank her most abusive children.

    “The U.S. temperatures in the summer of 2012 are an example of a new trend of
    outlying seasonal extremes that are warmer than the hottest seasona ltemperatures of the mid 20th century,” .
    “The climate dice are now loaded. Some seasons still will be cooler than the
    long-term average, but the perceptive person should notice that the frequency of
    unusually warm extremes is increasing. It is the extremes that have the most impact on people and other life on the planet.”GISS director James E. Hansen

  • Ford Prefect

    Good point. Doing both makes sense. Using one as an excuse to continue the current bad practices doesn’t make sense.

  • Indigo

    What’s to disobey?

  • It’s the staggering belief that global warming is solely the invention of a cabal of Commie scientists that I find the most gobsmacking. As I’ve wondered before, how do the right-wingers imagine this conspiracy works, and why? How did it somehow extend to almost every atmospheric scientist anywhere in the world? What are they supposed to be getting out of perpetrating what’s claimed to be a gigantic lie? The closest I’ve ever seen to an answer is the ludicrous claim that it’s all a scam to get grant money.

    There’s a bit of projection going on here, I suspect. On the evidence, “conservative principles” are rather shaky and mutable things. Republicans say one thing when their guy is President, another when the Democrats hold office. So if you are just making up your “principles” as you go along, saying one thing and then another depending on who’s in power, you’re probably disposed to think that what anyone says, even a scientist, is just a calculated power play.

  • I can only refer you to the answer I made to C. Publius below. I’m not saying that we should look into carbon sequestration instead of trying to lower carbon dioxide emissions, only that we should consider it as a last-ditch, admittedly short-term way to keep global warming in check until longer-term measures are put into place.
    If they are put into place. The current state of progress isn’t encouraging, is it?

  • Oh, no question about it. Only a sharp reduction of the actual emission of carbon dioxide is the only viable answer in the long term. I’m just wondering though if there’s any way we can minimize the damage now. I’m sure you’re aware, because you seem to have an excellent grasp of the matter, that atmospheric carbon dioxide concentration is already so high that even with an absolute cessation of emissions we’re in for a rough ride. I’m certainly not proposing massive carbon sequestration as a substitute for reduction of carbon dioxide emission, only as a measure of desperation to minimize the damage that’s already been done.

  • Ford Prefect

    While I’m sympathetic to the idea of technical means for sequestration, it seems mostly a ruse for Big Carbon to continue with the status quo than anything else: “We don’t have to change the way we do things, because we’ll spend Trillions on this techno-fantasy and solve the problem!”

    The problems with this are manifold: 1) It involves developing non-existent technology, which will be extremely expensive and take a long time; 2) We don’t know if any such scheme could really work, especially if we don’t change our energy system to one that’s sustainable without causing a mass extinction event. We don’t even want to spend money on solar power, so where will the money come from to pay for something that doesn’t even exist now?

    It would be far cheaper to simply reduce emissions. It would be far cheaper to put solar panels on every building than create stuff that doesn’t exist now. Either way, the nature of the economy is going to change, so why not do so proactively on things that actually work in the here and now?

    Since the argument against energy transition is based mostly on cost (not to mention corporate hegemony), how can we justify vastly more expensive “solutions” that probably won’t even work?

  • Dave of the Jungle

    Big Oil controls the world and it’s all about $$$.

  • Mighty

    So long as conservatives, including those in both GOP and Dems, can filibuster it won’t matter “science” data you bring forth because science is nothing but lies from the pits of hell to these people. I don’t know if we deserve to continue as a species. Perhaps mother nature will start over with the platypus as a model.

  • GaiusPublius

    Not as a natural process. For example, the Amazon forest will soon go from a carbon sink to a carbon source as deforestation continues.

    I don’t discount the possibility of a science breakthrough in sequestration — I’m certain people are working on it. But even with a break-through, we’ll have to stop dumping. And to do that, we have to de-enrich people like the Exxon CEOs, the Koch Bros, etc. That class of people is the main obstacle.

    Good question though. Thanks for asking it.


  • Naja pallida

    So our atmosphere CO2 levels now predates the genus Homo. Just the natural cycles of the Earth. Nothing to see here. Move along. What could possibly go wrong?

  • Is there any hope in carbon sequestration, do you think? There have been a number of plans proposed for this, ranging from the reasonable (but slow) to the outlandish (but fast). For instance, the nutty idea of dumping some sort of nutrient into the Pacific to encourage the formation of algal blooms that would “fix” a lot of carbon dioxide in a hurry has been propounded. Chemical means have also been proposed to convert carbon dioxide into carbonate minerals. Other methods have been devised I’m sure. It seems to me that some such method is going to be necessary since merely halting production of carbon dioxide will not be sufficient to stave off a large temperature rise. Actual removal of carbon dioxide would accomplish more.

  • Drew2u

    What about turning the CO2 and methane gasses solid and storing those in deepwater trenches?

  • Mike Meyer

    LAUNCH DRY ICE TO THE MOON. Store that CO2 safely for the long term. Pay for it with a CARBON TAX.

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