"Modern-day levels of carbon dioxide were last reached about 15 million years ago"

Scientific American summarizes two new studies giving evidence that the earth’s climate is highly sensitive to the amount of carbon dioxide in it. One is a a Science article by Aradhna K. Tripati, Christopher D. Roberts, and Robert A. Eagle. David Biello writes:

‘ “Modern-day levels of carbon dioxide were last reached about 15 million years ago,” Tripati says, when sea levels were at least 25 meters higher and temperatures were at least 3 degrees C warmer on average. “During the middle Miocene, an [epoch] in Earth’s history when carbon dioxide levels were sustained at values similar to what they are today [330 to 500 ppm [parts per million]], the planet was much warmer, sea level was higher, there was substantially less ice at the poles, and the distribution of rainfall was very different.”

Further, “at no time in the last 20 million years have levels of carbon dioxide increased as rapidly as at present,” Tripati adds; CO2 concentrations have climbed from 280 ppm to 387 ppm in the past 200 years. And “our work indicates that moderate changes in carbon dioxide levels of 100 to 200 parts per million were associated with major climate transitions and large changes in temperature”—indicative of a very sensitive climate.’

As I note in Engaging the Muslim World,, James Hansen, director of the Goddard Institute for Space Sciences, testified in 2008 that twenty years earlier he and his colleagues had worried that 450 parts per million of carbon dioxide in the atmosphere would trigger catastrophic climate change. But by the time of his testimony last year, Dr. Hansen and colleagues had concluded that 387 ppm was already catastrophic and that the world had to be taken back to the 280 ppm of the pre-industrial era if global calamities were to be avoided.

Hansen’s reasoning assumes that the world’s climate is sensitive to the amount of carbon dioxide in the atmosphere and has little “give” in this regard. The research cited by SA supports the “sensitive” argument.

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6 Responses

  1. Saw Secretary of Energy David Chu at MIT last Spring and heard him say that we are already at 440 ppm in CO2 equivalent, when you include the greenhouse effect of the other emissions we release like methane and methyl bromide and others. First time I've heard somebody put it that way. MIT, by the way, is very reluctant to talk about anything other than 450 ppm CO2.

    October 24 is a day of international attention to this issue to think about 350 ppm as the upper limit of CO2 in the atmosphere, meaning that we must remove carbon from the air starting today. Here in Cambridge, MA we will demonstrate our commitment by weatherizing some houses, something we have been doing once a month for over a year. Weatherization is a political act and we recognize it as such.

    Personally, I'd like to see a weatherization barnraising on the White House with full court TV coverage and a group of celebrity remodelers.

  2. The White House would be a nice place to start the drive for more efficient government buildings. But I would also like to see the LARGE office buildings of our gov. to switch to solar-panel windows.

    My scientific question is this though: If we have an ozone hole, are we 'releasing' any of the built up co2? i.e. how do we reduce what is already there?

    Should we send a low orbit satellite to "collect" any co2, should we "push" the co2 out of the atmosphere? Or do we just sit back and wait?

    These are the questions I have always asked, but no one has a solution BESIDES – cut, cut, cut emissions. It's an honorable position, to cut emissions, but this should already be happening because of our scientific knowledge of waste, and how to reduce it.

    What new tech, or old tech is being used to REMOVE the CO2 that our parents, grandparents, and great grandparents put up there?

    Sure our world is sensitive, and the hole may actually be saving us from more worldwide calamities. Any evidence that our world can correct itself without wiping out the known lifeforms?

  3. This warming is not a repeat of historical events. It is new, and worse.

    Some of the problems:

    1) Warming will continue and most likely increase. Effects of warming will continue to increase in severity. Zombie/religious warming-deniers will become bigger problems even as the warming problem becomes more severe.

    2) Ocean rise is just now starting up. Just now starting. Most ocean rise to date has been expansion of the water mass. A sea level rise of one meter is certain within forty years. It is only the first meter that counts. The first meter will displace hundreds of millions which will trigger wars.

    3) Sea level rise due to expansion will increase, but erosion of grounded maritime ice sheets an unknown factor which was not included in the IPCC report FOR THE REASON it was not quantifiable, poses the threat of catastrophically rapid rise, i.e. feet per decade or worse. Wars, etc.

    4) Soil moisture in fertile areas will decrease. Famine.

    5) Desynchronization of insect and flowering plant cycles, and rapid warming will make species migration impossible.

    There's more but that's enough. Religious nuts expect God to save us. I think nature will cull us.

    A clue for those who would be informed: see what James Lovelock has to say.

  4. Having been aware of the problem for twenty years, it's hard to see what we can do to reduce the CO2 concentration in the near term. The amount of energy locked into this component of our atmosphere is enormous, which is why we are so fond of fossil fuels.

    Radical action (a prohibitive carbon tax) is absolutely required if we are to cut our overall energy consumption down to a small fraction of what it is today. Even with that, we had better brace for impact, and prepare to ride out 450 ppm if we can.

  5. I am not a scientist, but i had a dream that tree's were breathing in CO2 and breathing out yummy O2….but then humans started chopping down all the tree's, and then they found it hard to breath.

  6. I have been stewing about our atmosphere being trashed for a long time. I was relieved to find the 350 movement,an advocacy group attempting to raise public awareness about the upper limits of carbon dioxide. They chose the # 350 as a slogan which translates well around the globe. 350 refers to 350ppm the concentration of carbon dioxide at which we might avoid the worst effects climate change. As JCole's blog quoted the US air is presently close to 487ppm so we need to reign in the fossil fuels. There are some 1800 "350 actions" in different countries around the world on October 24th. I am organizing one of three public events in Central Ohio at my church. I have never done anything like this before and maybe the turn-out will be lousy.(Oct 24th is the Saturday of the OSU homecoming football game) But I had to try something. When I asked acquaintances about the UN climate summit in Copenhagen this December most gave me blank looks. We are on the brink of natural calamity yet people around me seem anesthetized. There are innovative paths to reduce our carbon burning even so our "way of life" might have to be altered to have life at all. The implications of climate change are huge. Why don't we see a proportional response by our media, our leaders? Rhetorical I know. Big oil and big coal rule the day but short term profits betray the future. Wish me luck on community impact. Visit 350.org.

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