Hansen's Regression to Zero

While reading Hansen’s latest mailout I came upon an intriguing reference that I followed up. I suspect this paper is as important as Douglass et al. in describing an important way the models do not agree with the observations. It may be more important, in redefining the role of the Sun in recent warming.

His mailing contains a massive revision of his estimate of the rate of warming down from 0.2C per decade to 0.15C per decade. Near the end of his mailing he notes:

Solar irradiance has a non-negligible effect on global temperature [see, e.g., Reference 7, which empirically estimates a somewhat larger solar cycle effect than that estimated by others who have teased a solar effect out of data with different methods].

Reference 7, a paper by Tung, K.K., J. Zhou, C.D. Camp, Constraining model transient climate response using independent observations of solar-cycle forcing and response, recently published in Geophys. Res. Lett. in 2008 is freely available. It uses the geographical distribution of global temperature in response to the 11 yr solar cycle to isolate the transient climate response (TCR). Noting previously that the 19 IPCC models have a very large range in TCR, it compares the empirically derived TCR with the TCR of all the major IPCC climate models. The result is damning:

[14] The TCRs of 19 coupled atmosphere-ocean GCMs in IPCC AR4 listed in Table 1 fall within the rather low range of 1.2–2.2 K with the exception of one, and thus fail the lower constraint of 2.5 K determined by ERA-40, GISS and HadCRUT3. The only exception is the Japanese MIROC (hi-res), with a TCR of 2.6 K. All models fail the higher constraint of 3.6 K determined by the NCEP data.

The emphasis was added by the authors. As I understand it, they are saying that GCM’s have grossly underestimated solar forcing. Like the tropospheric ‘hotspot’ due to GHG’s in Douglass et al., they are not even in the right ballpark. The problem, it seems, is with the rate of transfer of heat into the ocean.

[16] It is seen that most of the current generation of general circulation models assessed by IPCC AR4 have too low a transient climate response as compared with the observed range. This is consistent with the independent finding by Forest et al. [2006] that these models simulate too large an ocean heat uptake as compared to observations of ocean temperature changes during the period 1961–2003. See Raper et al. [2002] and Meehl et al. [2004] for different views on how ocean heat uptake affects TCR. This excessive heat into the oceans tends to reduce the transient climate response for the atmosphere, but does not affect the modeled equilibrium climate sensitivity, which was calculated with a slab ocean in thermal equilibrium with the atmosphere.

The last sentence notwithstanding, there is an argument that underestimating TCR must lead to overestimating GHG forcing in the recent past. This would be a confirmation of the AGW skeptical view that recent response to solar forcing has been grossly underestimated, and GHG forcing exaggerated.

For the paper to be acknowledged by James Hansen himself is intriguing. Perhaps backpedaling is his way of avoiding jousting with jesters (climate skeptics).

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0 thoughts on “Hansen's Regression to Zero

  1. David – you’re off on the implications here: look at the definition of TCR (from the paper, first sentence in section 1):

    Transient Climate Response (TCR) is defined in
    IPCC 4th Assessment Report (AR4) as the global mean
    warming in response to 1% per year compound increase in
    CO2 at the time of its doubling.

    This paper is deducing from their analysis of the solar cycle that the climate is more sensitive to forcings – whether solar or CO2 – than has been previously estimated, where those forcings are defined relative to a given increase in CO2 levels, i.e. in terms of the GHG numbers, assumed given.

    Rather than your assumption that this proves “GHG forcing [has been] exaggerated”, this paper essentially argues the position that GHG forcing is whatever it is, but there are other negative forcings that have been underestimated to this point. The most likely candidate would be the large unknowns in aerosol numbers. This is small comfort, since we have no guarantee that those negative forcings will keep pace with increases in GHG’s, and this paper indicates the response to CO2 doubling would be on the order of their 3.6 K estimate, well past the high end of the IPCC estimates of 1.5 to 3 K for TCR). Not good for projections of warming this century, not good at all.

  2. David – you’re off on the implications here: look at the definition of TCR (from the paper, first sentence in section 1):

    Transient Climate Response (TCR) is defined in
    IPCC 4th Assessment Report (AR4) as the global mean
    warming in response to 1% per year compound increase in
    CO2 at the time of its doubling.

    This paper is deducing from their analysis of the solar cycle that the climate is more sensitive to forcings – whether solar or CO2 – than has been previously estimated, where those forcings are defined relative to a given increase in CO2 levels, i.e. in terms of the GHG numbers, assumed given.

    Rather than your assumption that this proves “GHG forcing [has been] exaggerated”, this paper essentially argues the position that GHG forcing is whatever it is, but there are other negative forcings that have been underestimated to this point. The most likely candidate would be the large unknowns in aerosol numbers. This is small comfort, since we have no guarantee that those negative forcings will keep pace with increases in GHG’s, and this paper indicates the response to CO2 doubling would be on the order of their 3.6 K estimate, well past the high end of the IPCC estimates of 1.5 to 3 K for TCR). Not good for projections of warming this century, not good at all.

  3. Arthur: Your interpretation doesn’t seem to gel with Hansen’s who said it “empirically estimates a somewhat larger solar cycle effect”. Is what you are saying in the paper? Are you saying that the paper says GCMs are out of the ballpark in overall sensitivity, on the low side?

  4. Arthur: Your interpretation doesn’t seem to gel with Hansen’s who said it “empirically estimates a somewhat larger solar cycle effect”. Is what you are saying in the paper? Are you saying that the paper says GCMs are out of the ballpark in overall sensitivity, on the low side?

  5. David – yes, the paper estimates a larger solar cycle effect, and consequently, since both solar forcing and GHG forcings are well known, a larger GHG effect as well.

  6. David – yes, the paper estimates a larger solar cycle effect, and consequently, since both solar forcing and GHG forcings are well known, a larger GHG effect as well.

  7. OK that is your logic, but where does the paper say that? It, and Hansen only refer to solar. What of the argument that the magnitude of GHG forcing has largely been estimated by ‘ dividing up the pie’ of total forcing, and in this zero sum, underestimating solar influence enhances other influences?

  8. OK that is your logic, but where does the paper say that? It, and Hansen only refer to solar. What of the argument that the magnitude of GHG forcing has largely been estimated by ‘ dividing up the pie’ of total forcing, and in this zero sum, underestimating solar influence enhances other influences?

  9. Yes, Arthur, you still have to absorb the change “…. contains a massive revision of his estimate of the rate of warming down from 0.2C per decade to 0.15C per decade. ” If there is more solar irradiance now than predicted, there must be less GHG effect.

    Besides, the ground and sea temperatures are so full of errors and wishful thiking that nothing of value can be calibrated against them.

  10. Yes, Arthur, you still have to absorb the change “…. contains a massive revision of his estimate of the rate of warming down from 0.2C per decade to 0.15C per decade. ” If there is more solar irradiance now than predicted, there must be less GHG effect.

    Besides, the ground and sea temperatures are so full of errors and wishful thiking that nothing of value can be calibrated against them.

  11. Arthur,

    I think I understand what you are trying to say. That is, the measurements of the actual change in sun output hasn’t changed, therefor the sensitivity of the earth system to that change must be increased to account for his findings.

    This may not be true, as mentioned above, as forcings are a zero sum game. If one is increased other(s) must be decreased to keep the result the same. The sum has been explicitly reduced by Dr. Hansen. That would imply an even greater decrease in the rest of the positive forcings, and/or, increase in negative forcings.

    You also seem to be ignoring the work by Dr. Spencer on water vapor negative forcing which is NOT going away anytime soon.

  12. Arthur,

    I think I understand what you are trying to say. That is, the measurements of the actual change in sun output hasn’t changed, therefor the sensitivity of the earth system to that change must be increased to account for his findings.

    This may not be true, as mentioned above, as forcings are a zero sum game. If one is increased other(s) must be decreased to keep the result the same. The sum has been explicitly reduced by Dr. Hansen. That would imply an even greater decrease in the rest of the positive forcings, and/or, increase in negative forcings.

    You also seem to be ignoring the work by Dr. Spencer on water vapor negative forcing which is NOT going away anytime soon.

  13. For me the telling statement in Tung et al is

    “Therefore the annual rate of increase in radiative
    forcing of the lower atmosphere during the five years from
    solar min to solar max happens to be equivalent to that from
    an average 1% per year increase in greenhouse gases, close
    to that used in TCR calculations.”

    which means to me that a prolonged solar minimum should bring GW to a halt, not reverse it. Tung does not challenge the IPCC AGW scenario (good for job security).

    On the other hand, if CO2 sensitivity is zero or very small we can expect temperatures to slide for about 20 years, as there is no such thing as one weak solar cycle. Time will tell.

  14. For me the telling statement in Tung et al is

    “Therefore the annual rate of increase in radiative
    forcing of the lower atmosphere during the five years from
    solar min to solar max happens to be equivalent to that from
    an average 1% per year increase in greenhouse gases, close
    to that used in TCR calculations.”

    which means to me that a prolonged solar minimum should bring GW to a halt, not reverse it. Tung does not challenge the IPCC AGW scenario (good for job security).

    On the other hand, if CO2 sensitivity is zero or very small we can expect temperatures to slide for about 20 years, as there is no such thing as one weak solar cycle. Time will tell.

  15. Arthur #1

    “….this paper essentially argues the position that GHG forcing is whatever it is, but there are other negative forcings that have been underestimated to this point. The most likely candidate would be the large unknowns in aerosol numbers. This is small comfort, since we have no guarantee that those negative forcings will keep pace with increases in GHG’s, and….”

    Actually, Arthur, I think you will find that there is a significant body of recent literature to suggest that:

    (1) by far the bulk of aerosols in the atmosphere are biogenic organic aerosols (isoprenes etc) and biogenic inorganic aerosols (sulfate from DMS etc) which are sourced from the continental (photosynthetic) living plant biomass and the oceanic cyanobacterial (also photosynthetic) biomass;

    (2) the size of these living biomasses is increasing with increased atmospheric CO2 (CO2 fertilization effect) i.e. trending upwards ; and

    (3) these aerosols not only have a negative forcing in their own right but also increase the rate of nucleation and opacity of clouds (water aerosols).

    Thus there are very good reasons to believe these negative forcings will keep pace with rising GHGs.

    Indeed the proven increased greening of the continents over the last 30 years or so and the increasing negative offset of CO2 levels over the 8 – 9 monitoring stations over the Southern Ocean from 30S to the South Pole below the global average CO2 suggests that these negative forcings will not only keep pace but are actually slowly increasing in magnitude. I have demonstrated this latter effect elsewhere from an analysis of official NOAA CO2 data 1982 – 2007 and could email you the data spreadsheet if you wish.

  16. Arthur #1

    “….this paper essentially argues the position that GHG forcing is whatever it is, but there are other negative forcings that have been underestimated to this point. The most likely candidate would be the large unknowns in aerosol numbers. This is small comfort, since we have no guarantee that those negative forcings will keep pace with increases in GHG’s, and….”

    Actually, Arthur, I think you will find that there is a significant body of recent literature to suggest that:

    (1) by far the bulk of aerosols in the atmosphere are biogenic organic aerosols (isoprenes etc) and biogenic inorganic aerosols (sulfate from DMS etc) which are sourced from the continental (photosynthetic) living plant biomass and the oceanic cyanobacterial (also photosynthetic) biomass;

    (2) the size of these living biomasses is increasing with increased atmospheric CO2 (CO2 fertilization effect) i.e. trending upwards ; and

    (3) these aerosols not only have a negative forcing in their own right but also increase the rate of nucleation and opacity of clouds (water aerosols).

    Thus there are very good reasons to believe these negative forcings will keep pace with rising GHGs.

    Indeed the proven increased greening of the continents over the last 30 years or so and the increasing negative offset of CO2 levels over the 8 – 9 monitoring stations over the Southern Ocean from 30S to the South Pole below the global average CO2 suggests that these negative forcings will not only keep pace but are actually slowly increasing in magnitude. I have demonstrated this latter effect elsewhere from an analysis of official NOAA CO2 data 1982 – 2007 and could email you the data spreadsheet if you wish.

  17. From the mail out:

    Indeed, subsurface and surface tropical ocean temperatures suggest that the system is “recharged”, i.e., poised, for the next El Nino, so there is a good chance that one may occur in 2009.

    Data here from NOAA suggests another La Nina is in the offing. By the way the composite figure for SON quarter has been adjusted up from -0.1 to 0.0 since last month.

  18. From the mail out:

    Indeed, subsurface and surface tropical ocean temperatures suggest that the system is “recharged”, i.e., poised, for the next El Nino, so there is a good chance that one may occur in 2009.

    Data here from NOAA suggests another La Nina is in the offing. By the way the composite figure for SON quarter has been adjusted up from -0.1 to 0.0 since last month.

  19. David: I tend to agree with you but we wouldn’t want to be accused of being unscientific so do you think there might be strong statistical support for that?;)

  20. David: I tend to agree with you but we wouldn’t want to be accused of being unscientific so do you think there might be strong statistical support for that?;)

  21. Jan: Or partisan. Perhaps you could call it a left-wing sentiment indicator. I think the left are wrong all of the time 😉 (but the right are wrong only most of the time).

  22. Jan: Or partisan. Perhaps you could call it a left-wing sentiment indicator. I think the left are wrong all of the time 😉 (but the right are wrong only most of the time).

  23. Lief Svalgaard (the infatigable solar debunker) is sceptical of the Camp&Tung paper. He points out that the solar TSI forcings changes by 100 times as much as the earth goes from solstice to solstice. If the direct effect of TSI explains the correlation that Camp&Tung found then it should be possible to find a seasonal signal that must 100 times as large (Leif claims the season signal does not exist).

    I am also sceptical of Camp&Tung’s findings because if you compare the solar cycle to ENSO you will see that minimums have La Ninas and the rising edge of the maxs have El Ninos. This means that Camp&Tung could be picking up the ENSO signal.

    Of course, it could mean that there is a link between ENSO and the solar cycle but that would be an entirely new mechanism and would invalidate all of the modelling work done to date.

  24. Lief Svalgaard (the infatigable solar debunker) is sceptical of the Camp&Tung paper. He points out that the solar TSI forcings changes by 100 times as much as the earth goes from solstice to solstice. If the direct effect of TSI explains the correlation that Camp&Tung found then it should be possible to find a seasonal signal that must 100 times as large (Leif claims the season signal does not exist).

    I am also sceptical of Camp&Tung’s findings because if you compare the solar cycle to ENSO you will see that minimums have La Ninas and the rising edge of the maxs have El Ninos. This means that Camp&Tung could be picking up the ENSO signal.

    Of course, it could mean that there is a link between ENSO and the solar cycle but that would be an entirely new mechanism and would invalidate all of the modelling work done to date.

  25. Raven: That makes sense. The thing that worried me about the paper was it sounded too simple. In the real world factors can’t be isolated so easily.

  26. The funny thing is if you google Camp&Tung Svalgaard you will find a post on tamino where the AGW boosters are agreeing that Svalgaard is right and Camp&Tung must be picking up a spurious signal. I wonder what they would say now that the Oracle has decided that Camp&Tung is required to avoid admiting the models are flawed.

  27. The funny thing is if you google Camp&Tung Svalgaard you will find a post on tamino where the AGW boosters are agreeing that Svalgaard is right and Camp&Tung must be picking up a spurious signal. I wonder what they would say now that the Oracle has decided that Camp&Tung is required to avoid admiting the models are flawed.

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