Some of the CO2 feedback in climate models are wrong by up to 80%. The science is not settled. CO2 feedback recalculated : Nature Amplification of global warming by carbon-cycle feedback significantly less than thought, study suggests "In this week's Nature, David Frank and colleagues extend this empirical approach by comparing nine global-scale temperature reconstructions with CO2 data from three Antarctic ice cores over the period ad 1050-1800. The authors derive a likely range for the feedback strength of 1.7-21.4 p.p.m.v. CO2 per degree Celsius, with a median value of 7.7. The researchers conclude that the recent estimates of 40 p.p.m.v. CO2 per degree Celsius can be excluded with 95% confidence, suggesting significantly less amplification of current warming."
Science is never settled - we can always learn more (if we keep our minds open, and continue to research the facts). This is good news, but it seems to be nearly insignificant in comparison to the CO2 still being added from man-made sources - so you can still plan on a warming planet.
(and by "the facts", I mean ALL the facts, not just the ones you choose to post in support of your conspiracy-theories of a world-wide hoax by a coalition of thousands of experts from dozens of countries)
Some studies are using a doubling of CO2 in their models. Those results are now dubious. But my guess is that they will still be relied upon by policy makers and cheerleaders.
Facts that are in error, are not facts. Scientists who error by 80% are either stupid as hell,or influenced by $79,000,000,000.
"Using 200,000 data points, the study – believed by "Nature" to be the most comprehensive of its kind so far"
Re: #4, the CO2 doubling derives from projections of fossil fuel combustion, not from gamma (the bulk temperature sensitivity of net respiration of biospheric organic carbon). This is not a trivial distinction and I wish folks would to their best to grasp that. By no means is this gamma easy to pin down. The modeling done here helps, as do the many studies done on warming terrestrial ecosystems. This study is probably closer to my own research chasing carbon around forests, than any that have been discussed here. Therefore I feel quite confident to say that we will have to consider several factors beyond temperature before our understanding of gamma becomes clear. I hope opoonents to funding research on earth system science don't mind too much if that work continues. Thanks Meanwhile, Frank et al. used temperature reconstructions that would be called "Mann's hockey stick" rather than "Soon and Baliunas Medieval was warmer than now" here at PriusChat. It may not have been the OP's intention to emphasize that point, but I believe that it is well worth reflecting upon. We have discussed Medieval climate a lot here.
Knowing exactly where CO2 levels (and average temps) will be in 90 years is impossible. Masturbate the numbers all you want, you'll never hit it spot on. But the general direction is OBVIOUS.
Hi Tom, judging from your choice of verb in responding, I must have hurt your feelings. I apologize, it was not my intention. The CO2 emissions projections include uncertainties related to economic development and the growth of energy conservation and low-carbon energy technologies. The fraction of that CO2 that remains in the atmosphere depends on biological processes on land and at sea. It is currently about 50%, but we cannot be sure that fraction will persist unchanged. At sea, for example, both temperature and acidity changes would argue for lower uptake in the future. These are in addition to the gamma factor discussed earlier. One intent of the IPCC assessments (it seems to me) was to consider that full range of variation going forward. I reckon that neither of us would require exact knowledge of future CO2, to discuss the pluses and minuses of our various possible responses.
Let's do this one as a Q and A: Q: This "feedback", is that the effect of C02 on temperature? A: No, this is the tendency for a higher temperature to "cook" more carbon out of the biosphere into the atmosphere, when the atmosphere-biosphere carbon exchange is nearly in equilibrium. Q: But wait, isn't the biosphere absorbing carbon right now, not outgassing it, on net? A: Yes, about half the carbon we put into the atmosphere annually, now, gets absorbed, mostly by the ocean (hence, ocean adicification as C02 turns to carbonic acid). Q: So, this paper isn't talking about the man-made carbon emissions that drive warming today? A: No, in principle, this is talking about the extent to which nature, will, eventually, amplify manmade carbon emissions by off-gassing even more carbon. In practice, the way that works out in the IPCC simulations is, the higher the gamma, the sooner you expect the biosphere to slow down the rate at which it is absorbing carbon. (In other words, it doesn't outright outgas carbon no net, it just absorbs less carbon.) And so, the higher the expected atmospheric C02 in (say) the year 2100. Q: But wait, how can they say that the biosphere releases carbon when it warms, while we see the biosphere absorbing carbon, while it is warming? A: It's all about equilibrium. They looked at a period in which the atmosphere and biosphere were pretty close to being in equilibrium. Minor shifts in temperature would drive C02 into or out of the biosphere. (Another way to look at that is that if ONLY the temperature changes, you'll see those swings in C02 -- as during the orbitally-driven ice ages.) We, by contrast, live in an era where we've pumped up atmospheric C02 to a level that's about one-third above the equilibrium. We have higher temperatures AND far-above-equilibrium atmospheric carbon. So, the net effect we get is the combined impact of those two factors. So, on net, we're seeing atmospheric carbon being driven into the ocean. But what we see as the net effect of carbon moving from air to ocean is being affected by temperature. This gamma thingy, that's overlaid on top of the main effect that we are causing. It slows down the rate at which the biosphere is absorbing carbon. That's where this study may help inform the IPCC projections. Q: How did they estimate this feedback from temperature to atmospheric carbon? A: The took Mann-style temperature reconstructions for the past 1000 years, and related fluctuations in temperature to fluctuations in atmospheric C02, measured from antarctic ice cores. Q: So, no rational individual who bothered to read the (abstract of) the study would both post anti-Mann screeds and post this, would he? A: No, that would be logically inconsistent. You have to believe in Mann and similar analyses in order to give any credence to this one. Q: Ditto for anybody who doesn't believe the antarctic ice core records of atmospheric C02? A: Nope, the nutters who think C02 ping-ponged up and down just prior to the modern era (1950s) are also excused from believing this one. Q: But, wait. I thought we were expecting to see all kinds of carbon feedbacks that never occurred over the past milllenium. For example, we're now seeing the permafrost melt and offgas methane. We're seeing plumes of methane from ocean-floor clathrate deposits. We're seeing the acidity of the sea level rise at an unprecedented rate. We have models projecting that (e.g.) the US Southwest has a high probability of entering a permanent dustbowl state (thus releasing carbon stored in soil and plants there). How does this study account for those feedback mechanisms that were not in operation during the study period? A: Well, it doesn't. That study was very much a macro-level analysis of temperature and CO2 variations that occurred in the recent past. There was no attention to the details of the mechanisms that caused that feedback. The authors make a reasoned argument that, probably, changes will be small enough that, over the near term (next century) that their new, lower estimate of feedback is relevant to projecting temperatures through 2100. Q: But how can they know that? A: They can't. They made a reasoned argument. Let's face it: we're in uncharted territory, as far as global temperatures and atmospheric C02 levels go, and we're heading farther into the unknown. The earth hasn't seen C02 levels like these for at least hundreds of thousands of years (ice cores) and probably tens of millions of years (less direct evidence). The temperature appears unprecedented over the past 1000 years, and may be for a longer span. Q: Is the IPCC aware of all this uncertainty? A: Yes, of course. If you want to read up on it, chapter 10 of the physical science basis of the 2007 report discusses model projections with different assumptions about gamma. Here's what the executive summary of the carbon cycle analysis: AR4 WGI Chapter 10: Global Climate Projections - 10.ES.6 Carbon Cycle "There is unanimous agreement among the coupled climate-carbon cycle models driven by emission scenarios run so far that future climate change would reduce the efficiency of the Earth system (land and ocean) to absorb anthropogenic CO2. As a result, an increasingly large fraction of anthropogenic CO2 would stay airborne in the atmosphere under a warmer climate. For the A2 emission scenario, this positive feedback leads to additional atmospheric CO2 concentration varying between 20 and 220 ppm among the models by 2100. Atmospheric CO2 concentrations simulated by these coupled climate-carbon cycle models range between 730 and 1,020 ppm by 2100. Comparing these values with the standard value of 836 ppm (calculated beforehand by the Bern carbon cycle-climate model without an interactive carbon cycle) provides an indication of the uncertainty in global warming due to future changes in the carbon cycle. In the context of atmospheric CO2 concentration stabilisation scenarios, the positive climate-carbon cycle feedback reduces the land and ocean uptake of CO2, implying that it leads to a reduction of the compatible emissions required to achieve a given atmospheric CO2 stabilisation. The higher the stabilisation scenario, the larger the climate change, the larger the impact on the carbon cycle, and hence the larger the required emission reduction. " Q: So, we're cooked, with or without this result? A: Yes, that's how I read that. Our emissions are adequate to do that. But this remains an important question, because if the earth will continue to absorb carbon at a higher rate, we don't have to cut emissions as much to reach any particular C02 target. Q: Just to be perfectly clear, this "possible 80% overstatement" of the feedback, that doesn't mean that the IPCC overstated expected temperature increases by 80%, does it. A: No, not even close. Per above, the gamma factor is icing on the cake. Q: So this study is the last word on this, right? I mean, we can just scrap all other evidence in this area and take this as Gospel? A: No, it's an interesting piece of evidence, but not the only one. Basically, they had nine (I think that's right) temperature reconstructions, plus C02 measurements, over about a 1000 year period. It's not clear that this trumps all prior studies. But it is interesting new information.
