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For a more rigorous, scientific and yet still thoroughly digestible talk I strongly recommend watching Dr. Richard Alley's talk "The Biggest Control Knob: Carbo

For a more rigorous, scientific and yet still thoroughly digestible talk I strongly recommend watching Dr. Richard Alley's talk "The Biggest Control Knob: Carbon Dioxide in Earth's Climate History" [0] As a Bayesian I particularly enjoy Alley's running theme that: while there certainly could be alternative explanations for what is happening, we simply cannot find anything that explains the data better than CO2. I see many skeptics pointing out tiny holes in the main AGW hypotheses, but the real Bayesian test is "how much better does one hypothesis explain the observed data than then other?". When you put all the pieces of the atmospheric CO2 argument together it seem to explain what we're observing dramatically better than a thousand "...but what about?" that don't fit together into a coherent counter hypothesis. As an example: Suppose I come home and see my front window broken, my door open and my laptop missing. I assume I have been robbed based on this evidence. You could say "but couldn't the window have been broken by some kid throwing rocks?", "maybe you left the door unlocked and the wind blew it open", "are you absolutely sure you didn't leave your laptop at work?" While individually each of these counter hypotheses may explain a single event just as well, together they don't work: P(window broke, door open, laptop missing | robbed) x P(robbed) >> P(window broke, door open, laptop missing | neighbor threw rock, left door unlocked and left laptop at work) x P(neighbor threw rock & left door unlocked & left laptop at work). [0] https://www.youtube.com/watch?v=RffPSrRpq_g https://www.youtube.com/watch?v=RffPSrRpq_g edit: forgot to add my priors in that last section

ABCLAW 10y ago
Thank you for the link. This is a fantastic lecture that presents a very accessible synthesis of geologic and atmospheric science. Starts off a bit slow, but I suggest sticking with it. It addresses a number of the arguments presented in this thread.
- graycat 10y ago
  I just watched it: It has a lot of interesting stuff on time scales of some millions or billions of years. Yup, in particular, there have been some huge swings in temperature and CO2 concentrations and big effects in weathering rocks, the pH of the oceans, what plants have to do differently in their breathing in response to big CO2 concentration changes, etc. He wants to claim "The Biggest Control Knob: Carbon Dioxide in Earth's Climate History". It does appear that he argued that CO2 is a big indicator of temperature changes. He brings in some surprising ideas that with big changes in temperature from whatever cause, CO2 turns out to be nearly necessarily an indicator. Okay. But, I'm not seeing that his interesting stuff says that CO2 is a control. He discusses two big causes of big temperature changes, and neither is CO2: His first cause is that some many millions of years ago, the sun gave the Earth about 30% less solar energy because the sun was cooler because it was burning more hydrogen, thus, converting it to helium and later got warmer because it had more helium. He does confess that we have poor data on how much cooler the sun was. But he goes on to say that it was clear that then the Earth had liquid water, and for this it needed to have the greenhouse effect of CO2 to keep the water from freezing. So, if believe that some many millions (some billions) of years ago the sun was significantly cooler, then maybe a CO2 greenhouse effect kept some of the water from freezing. Other ways to keep the water from freezing? Maybe volcanoes, radioactive decay of rocks, asteroid strikes, dust, water vapor, methane in the atmosphere, maybe more? But, okay, maybe in an extreme situation of a few billion years ago with an Earth atmosphere with a lot of CO2 (didn't yet have plants converting CO2 to O2), maybe also methane and water vapor, maybe clouds of dust, etc. the CO2 did help warm the Earth. But here the control was the cooler sun, not the CO2. His second cause was some effects of the Earth's orbit or some such. So, that effect caused several periods of global cooling that can be seen in the ice core samples going back 800,000 years. He states clearly that CO2 did not cause that cooling, that as he mentioned the orbit did. But then he goes on to explain how with the cooling there got to be more CO2 and, then, some warming he attributes to the extra CO2. But, again, the control was the orbit, not the CO2. His arguments are interesting, but his case is big swings in temperature and CO2 concentrations over millions of years with lots of big effects from the sun, the Earth's orbit, volcanoes, geology (weathering of rocks), pH of the oceans, huge changes in the oceans (e.g., lots of hydrogen sulfide), etc. He's not really talking about some significant effect of Joe's gasoline powered lawnmower on the temperature in NYC in year 2050 thus justifying carbon taxes on Joe's gasoline.
  - acqq 10y ago
    > He's not really talking about some significant effect of Joe's gasoline powered lawnmower on the temperature in NYC in year 2050 thus justifying carbon taxes on Joe's gasoline. Of course not. First "on the temperature in NYC" is wrong. The topic is the whole Earth. Second it's not "Joe's gasoline powered lawnmower" that we worry about, but the amount of CO2 pushed by the whole Earth, all actions of all humans, measured in billions of tonnes of carbon per year! Third the scientists don't do anything about the "carbon taxes" (at least not the climate scientists) that's what the politicians (and economists) claim "has sense." The scientists just say "don't push that much CO2, the results can be very bad." See: http://www.ipcc.ch/report/ar5/wg3/ http://www.ipcc.ch/report/ar5/wg3/ specifically "Summary for Policymakers and Technical Summary": http://ipcc.ch/pdf/assessment-report/ar5/wg3/ipcc_wg3_ar5_summary-for-policymakers.pdf http://ipcc.ch/pdf/assessment-report/ar5/wg3/ipcc_wg3_ar5_su... It has different "mitigations" analyzed but it's the politicians that do the things.
    - graycat 10y ago
      I suspect that we are mostly in agreement but are not reading English the same way. What I said about Joe, a generic guy, his lawnmower, a generic emitter of CO2, gasoline, a generic source of carbon to burn, and NYC, a generic city highly interested in CO2 and pushing carbon taxes, were all generic examples; looks like I should have had a prefix of "such as". But my main point was that the lecture was talking about wildly different scales than what we are seeing on Earth now or likely for, say, the rest of this century. Or, the lecture was talking about really extreme, very different, conditions -- due to a cooler sun and the earth's orbit -- over 800,000 years to many millions of years. Heavily he was discussing geology, that is, a science of really slow changes, from volcanoes, huge swings in the chemistry of the air and water of earth, etc. For your "billions of tonnes of carbon per year", I don't know what to think about that, that is, I don't know what to compare it with so don't know if that amount is, for all of the earth and sources of CO2, methane, etc. just a tiny, insignificant, nearly invisible drop in the total bucket or a major change. E.g., I have yet to see good data on how much CO2 and/or methane comes from volcanoes, on land and in the oceans, year by year. E.g., how much CO2 is dissolved in the upper, say, 2000 feet of the oceans, and if the temperature of that water is increased by, say, 1 degree C, how much of that CO2 will escape into the atmosphere? My point here is, I'm short on information to evaluate the quantities involved here, e.g., your "billions". It was an interesting talk, e.g., with lots of really cute chemistry -- I wish my chemistry courses had had that much depth. I can see how geologists, e.g., in the AGU, could get really involved. Or, the lecture should be really popular on some Web site like HN but GN for Geology News! But I see very little relevance in that lecture for the current intense discussions leading to carbon taxes, etc., which seem to be of high concern on HN. E.g., if the sun gets 30% cooler, then we might want to review the lecture, if anyone is still here! Or, if the earth has an orbit situation such as in the several cases of global cooling that show in the ice cores from 800,000 or so years ago, then maybe we should rush to add all the CO2 to the atmosphere we could and otherwise risk big ice sheets in Kansas, Texas, Panama, or some such? But these cases, along with the big asteroid hit of 65 million years ago, the huge volcanoes of the Russian traps, when India moved north, hit South Asia and pushed up the Himalayas, even when Yellowstone blew and put, IIRC, ash 1000 feet deep 1000 miles down wind, are super major biggie causes of disaster, and, of course, if a gamma ray burst popped off somewhere in our part of our galaxy, as far as I can tell, that make everything humans are doing now just an invisible, trivial nit. From all I've seen, if we want to talk about human sources of CO2 and their contributions to significant global warming for the rest of this century, then we have a lot of really hard work to do. Why? (1) A lot of work was done trying to predict what the realistic CO2 levels would do to global temperatures, and now we can see that nearly all the temperature predictions from that work were way, way too high. (2) In a sense, we know too much: E.g., we know that the fluid flows, both in the atmosphere and the oceans, satisfy the Navier-Stokes equations of fluid flow. So, first cut, we would have to solve those equations for the surface of the earth, on both land and the oceans. And we would have to include the effects of all the solar and infrared radiation involved. Then, even to get started, we would need the current initial conditions, e.g., what the volcanoes were doing, and we are a long way from knowing those. Then, we would be very short on a suitable computer. Sure, we'd like to take an approach easier than (2), but as in (1) that easier approach was nearly all wildly inaccurate. With (2), we are stuck, or stuck-o. But the lecture had some amazing geology and chemistry!

ABCLAW 10y ago

Thank you for the link. This is a fantastic lecture that presents a very accessible synthesis of geologic and atmospheric science. Starts off a bit slow, but I suggest sticking with it. It addresses a number of the arguments presented in this thread.

graycat 10y ago
I just watched it: It has a lot of interesting stuff on time scales of some millions or billions of years. Yup, in particular, there have been some huge swings in temperature and CO2 concentrations and big effects in weathering rocks, the pH of the oceans, what plants have to do differently in their breathing in response to big CO2 concentration changes, etc. He wants to claim "The Biggest Control Knob: Carbon Dioxide in Earth's Climate History". It does appear that he argued that CO2 is a big indicator of temperature changes. He brings in some surprising ideas that with big changes in temperature from whatever cause, CO2 turns out to be nearly necessarily an indicator. Okay. But, I'm not seeing that his interesting stuff says that CO2 is a control. He discusses two big causes of big temperature changes, and neither is CO2: His first cause is that some many millions of years ago, the sun gave the Earth about 30% less solar energy because the sun was cooler because it was burning more hydrogen, thus, converting it to helium and later got warmer because it had more helium. He does confess that we have poor data on how much cooler the sun was. But he goes on to say that it was clear that then the Earth had liquid water, and for this it needed to have the greenhouse effect of CO2 to keep the water from freezing. So, if believe that some many millions (some billions) of years ago the sun was significantly cooler, then maybe a CO2 greenhouse effect kept some of the water from freezing. Other ways to keep the water from freezing? Maybe volcanoes, radioactive decay of rocks, asteroid strikes, dust, water vapor, methane in the atmosphere, maybe more? But, okay, maybe in an extreme situation of a few billion years ago with an Earth atmosphere with a lot of CO2 (didn't yet have plants converting CO2 to O2), maybe also methane and water vapor, maybe clouds of dust, etc. the CO2 did help warm the Earth. But here the control was the cooler sun, not the CO2. His second cause was some effects of the Earth's orbit or some such. So, that effect caused several periods of global cooling that can be seen in the ice core samples going back 800,000 years. He states clearly that CO2 did not cause that cooling, that as he mentioned the orbit did. But then he goes on to explain how with the cooling there got to be more CO2 and, then, some warming he attributes to the extra CO2. But, again, the control was the orbit, not the CO2. His arguments are interesting, but his case is big swings in temperature and CO2 concentrations over millions of years with lots of big effects from the sun, the Earth's orbit, volcanoes, geology (weathering of rocks), pH of the oceans, huge changes in the oceans (e.g., lots of hydrogen sulfide), etc. He's not really talking about some significant effect of Joe's gasoline powered lawnmower on the temperature in NYC in year 2050 thus justifying carbon taxes on Joe's gasoline.
- acqq 10y ago
  > He's not really talking about some significant effect of Joe's gasoline powered lawnmower on the temperature in NYC in year 2050 thus justifying carbon taxes on Joe's gasoline. Of course not. First "on the temperature in NYC" is wrong. The topic is the whole Earth. Second it's not "Joe's gasoline powered lawnmower" that we worry about, but the amount of CO2 pushed by the whole Earth, all actions of all humans, measured in billions of tonnes of carbon per year! Third the scientists don't do anything about the "carbon taxes" (at least not the climate scientists) that's what the politicians (and economists) claim "has sense." The scientists just say "don't push that much CO2, the results can be very bad." See: http://www.ipcc.ch/report/ar5/wg3/ http://www.ipcc.ch/report/ar5/wg3/ specifically "Summary for Policymakers and Technical Summary": http://ipcc.ch/pdf/assessment-report/ar5/wg3/ipcc_wg3_ar5_summary-for-policymakers.pdf http://ipcc.ch/pdf/assessment-report/ar5/wg3/ipcc_wg3_ar5_su... It has different "mitigations" analyzed but it's the politicians that do the things.
  - graycat 10y ago
    I suspect that we are mostly in agreement but are not reading English the same way. What I said about Joe, a generic guy, his lawnmower, a generic emitter of CO2, gasoline, a generic source of carbon to burn, and NYC, a generic city highly interested in CO2 and pushing carbon taxes, were all generic examples; looks like I should have had a prefix of "such as". But my main point was that the lecture was talking about wildly different scales than what we are seeing on Earth now or likely for, say, the rest of this century. Or, the lecture was talking about really extreme, very different, conditions -- due to a cooler sun and the earth's orbit -- over 800,000 years to many millions of years. Heavily he was discussing geology, that is, a science of really slow changes, from volcanoes, huge swings in the chemistry of the air and water of earth, etc. For your "billions of tonnes of carbon per year", I don't know what to think about that, that is, I don't know what to compare it with so don't know if that amount is, for all of the earth and sources of CO2, methane, etc. just a tiny, insignificant, nearly invisible drop in the total bucket or a major change. E.g., I have yet to see good data on how much CO2 and/or methane comes from volcanoes, on land and in the oceans, year by year. E.g., how much CO2 is dissolved in the upper, say, 2000 feet of the oceans, and if the temperature of that water is increased by, say, 1 degree C, how much of that CO2 will escape into the atmosphere? My point here is, I'm short on information to evaluate the quantities involved here, e.g., your "billions". It was an interesting talk, e.g., with lots of really cute chemistry -- I wish my chemistry courses had had that much depth. I can see how geologists, e.g., in the AGU, could get really involved. Or, the lecture should be really popular on some Web site like HN but GN for Geology News! But I see very little relevance in that lecture for the current intense discussions leading to carbon taxes, etc., which seem to be of high concern on HN. E.g., if the sun gets 30% cooler, then we might want to review the lecture, if anyone is still here! Or, if the earth has an orbit situation such as in the several cases of global cooling that show in the ice cores from 800,000 or so years ago, then maybe we should rush to add all the CO2 to the atmosphere we could and otherwise risk big ice sheets in Kansas, Texas, Panama, or some such? But these cases, along with the big asteroid hit of 65 million years ago, the huge volcanoes of the Russian traps, when India moved north, hit South Asia and pushed up the Himalayas, even when Yellowstone blew and put, IIRC, ash 1000 feet deep 1000 miles down wind, are super major biggie causes of disaster, and, of course, if a gamma ray burst popped off somewhere in our part of our galaxy, as far as I can tell, that make everything humans are doing now just an invisible, trivial nit. From all I've seen, if we want to talk about human sources of CO2 and their contributions to significant global warming for the rest of this century, then we have a lot of really hard work to do. Why? (1) A lot of work was done trying to predict what the realistic CO2 levels would do to global temperatures, and now we can see that nearly all the temperature predictions from that work were way, way too high. (2) In a sense, we know too much: E.g., we know that the fluid flows, both in the atmosphere and the oceans, satisfy the Navier-Stokes equations of fluid flow. So, first cut, we would have to solve those equations for the surface of the earth, on both land and the oceans. And we would have to include the effects of all the solar and infrared radiation involved. Then, even to get started, we would need the current initial conditions, e.g., what the volcanoes were doing, and we are a long way from knowing those. Then, we would be very short on a suitable computer. Sure, we'd like to take an approach easier than (2), but as in (1) that easier approach was nearly all wildly inaccurate. With (2), we are stuck, or stuck-o. But the lecture had some amazing geology and chemistry!