Re: [climate-change-forum] Re: Siberian permafrost thaw warning sparked by cave data
- On 28 February 2013 13:47, Mitchell J <oski00@...> wrote:> No, I didn't read this paper, which is a description of the model. I don't> need to read this paper to look at Fig. 3 and see that MAGICC6 isI see that they do have a projected 5'K increase or so projected for 2100 (from pre-industrial). This is more accurate than others that I have seen, certainly not the 2'K that I thought they were working with. They also project a 10'K rise by 2200 but who's counting past 2 generations around here right?
> projecting more warming than the CMIP5 models.
So what you mean is they project a worst case of 10 degrees by 2200 as the worst case sensitivity to worst case emissions scenario.
In general, your confidence that you know what the climate sensitivity is (and I refer to the wording of your assertion that 5 K is "more accurate") is very hard to understand.
The uncertainty in climate sensitivity has remained stubbornly in the range 1.5 - 4.5 K since the 1979 Charney Report, and the uncertainty is unlikely to come down any time soon. While there are differences of opinion on what the most likely value is, it's fair to say that there are few published PDFs that don't assign highest probability to the values around 2.5 - 3. Lately, of course, there has been a slew of papers assigning highest probability to values much lower - and I meant in the range of 2 - 2.5. And, there are papers arguing for values less than 2. As the RealClimate article I posted showed, there is at least one paper arguing for 4 K.
Thus, there is not a shred of support for your preferred value of over 4.5 K. Please show me a single recent paper that argues for a sensitivity so high. Meanwhile, regardless of all evidence, you seem to "know" this is the "truth". How can do this and still maintain in yourself a sense of intellectual coherence?
Polar amplification will accelerate as albedo shifts. The AR5 does not include the "sea change" that the loss of multi-year sea ice in 2012 brought on.
Okay, I haven't finished reading it. Can you show me a published paper that quantifies the effect of the sea change?
> > Now the high end of the SvD12 permafrost sensitivity requires the high endThis is one that we can (and do) certainly disagree on. However you attempt to measure it, the positive climate feedbacks brought on in this new period of the Anthropocene has absolutely no reference or similarity to paleoclimate analysis. All one needs to do is look to the arctic and realize that we are now experiencing runaway acceleration of feedbacks.
> > > of the model's climate sensitivity - something over 4.5 C / doubling of
> > CO2
> > > - which is as good as impossible.
This is not true.
Durian the Eemian period in the last interglacial it is very likely that the Arctic was summer ice free. If there were feedbacks waiting to "runaway" as soon as the summer ice melted, then we wouldn't be here discussing it. Correct?
> > not if you include all of the feedbacks. Remember, we already have locked
> > in over 2.5'C today (if you simply correct for Aerosols but don't include
> > arctic albedo and permafrost emissions.)
> Your aerosol beliefs, I hoped we could agree, are simply wrong.
> Subsequent to our discussion, I found something very interesting in the AR5
> SOD. You might also be interested in Table 8.7.
perhaps one of the hazards of quoting from a document that is still in review?
No, you are evidently misunderstanding Fig. 7.19. If you turn to the Chapter 7 executive summary:
The radiative and adjusted forcings due to aerosol-cloud interactions (RFaci and AFaci) are assessed to be –0.3 (–0.7 to 0) W m–2 and –0.4 (–0.9 to 0) W m–2. The AFaci is estimated as the residual between AFari+aci and AFari. These ranges reflect our understanding of aerosol-cloud interactions in liquid and ice clouds, in particular from observations and large-eddy simulations, which reveal some compensating effects. However they remain somewhat inconsistent with available estimates from climate models, which do not capture all of the relevant processes and tend to simulate more negative forcings. [7.5.2, 7.5.3, Figure 7.19]
That value is the same as given in Table 8.7.
Meanwhile, fig. 7.19 shows us that the actual satellite measurements (squares) have converged on a much smaller value for RFaci than predicted in earlier assessment reports by GCMs.
In summary, there is no observational support for your beliefs in higher than expected aerosol forcing. Your appeal to Fig. 7.19 suggests that only way you one can cling onto high values for AFaci and AFari is to ignore all the actual observational evidence and in favour of now-refuted GCM predictions.
This is due to self-censorship and the attempt to appear credible in the face of blatant (but admittedly effective) disinformation http://www.guardian.co.uk/environment/2013/feb/14/funding-climate-change-denial-thinktanks-network
> The important point is that scientists actually publishing papers are not
> sure about what's going to happen. It is strange therefore that you seem
> so sure where everyone else is unsure. So unsure is all this stuff that
> the AR5 has apparently chosen to stay completely silent.
Alright, and once you bring in the unfalsifiable Oreskes conspiracy theory, I'm not sure what you expect me to say. It's kind of like playing the race or gender card - a surefire way to shut down any rational discussion. Ockam's Razor would have it that if all publishing scientists assert they are unsure, the likeliest explanation for their assertions is that they really are unsure.> > > Alright, and there you go again essentially just making up your own data.And here is the crux of our communications difficulty. How many years of calculus and science-degree physics were you required to take for your degree? Do you have a "science-based" background or a "policy-based" background?
> > > If you can't support these numbers with reference to the peer reviewed
> > > literature it is highly misleading to assert them as facts, the way you
> > > always do.
> > http://www.nature.com/nature/journal/v361/n6412/abs/361520a0.html
> > http://www.esajournals.org/doi/pdf/10.1890/08-2025.1
> > http://www.nsf.gov/news/news_videos.jsp?cntn_id=114865&media_id=65190
> > and still these do not include the effect of a summer solstice ice free
> > arctic by 2027
> None of these refs support your numbers, which is the point.
> Also, let's suppose the Arctic does become ice free by 2027. That will
> mean that there is a much-weakened ice-albedo feedback for the period
> 2027-2100. Since we are interested in the warming caused by the permafrost
> feedback at 2100 it is not obvious to me that it makes any difference if
> the Arctic becomes summer ice free in 2027.
I am not a mathematician. I have a computer science and history and philosophy of science degree.
please try to understand what the cumulative effects of +5 W/m^2 of regional warming in the arctic during the summer months beginning in 2027 (vs say, 2080) and continuing through 2100 (and beyond) will do to that region, the polar amplification will easily be 5-7 times global mean surface temperature by this time. My estimates of an ice free arctic in the summer of 2027 are conservative.
And where did this factor of 5-7 come from? As above, the fact that the Arctic has been ice free before suggests that an ice free Arctic does not send the earth into a runaway postive feedback death spiral. My thoughts on what 5 W m-2 will do is it will raise the temperature during summer but it's not going to melt any ice if the ice is already melted.
Finally, the decimation of regional northern hemispheric grain production and the resultant flooding of population centers by this time will already make your arguments moot. We don't need another 1'K temperature increase (which by the way, is still what the removal of 35-80% of *current* SO2 emissions would produce) to find this out. It is already happening due to the arctic temperature shift and the Hadley Cell migration.
Okay, and as with the above, if you say so. You want your own unpublished private version of the science.
- --- In firstname.lastname@example.org, Alex Harvey <alexharv074@...> wrote:
>Read it again Alex,
> On 10 March 2013 08:46, Mitchell J <oski00@...> wrote:
> > **
> > Conclusions. Our analysis suggests that a sea-ice bifurcation
> > > > threshold (or "tipping point") caused by the icealbedo feedback
> > > > is not expected to occur in the transition from current perennial
> > > > sea ice conditions to a seasonally ice-free Arctic Ocean, but that
> > > > a bifurcation threshold associated with the sudden loss of the
> > > > remaining seasonal ice cover may occur in response to further
> > > > heating.
> > Eisenman and Wettlaufer, 2009
> And that is contradicted by Tietsche who do *not* find evidence for "*a
> bifurcation threshold associated with the sudden loss of the remaining
> seasonal ice cover*". You seem to be amazingly good at averting your gaze
> from statements that contradict your thinking.
E&W09 says, "a sea-ice bifurcation threshold (or "tipping point") caused by the icealbedo feedback is not expected to occur"
They are in agreement.
They are also in agreement with my original point:
The step level change in surface air temperature I was speaking of is only during the summer months after the sea ice is gone and is modeled in both papers. In E&W they model a 5-7K increase, in Teitsche '12 they model an 11K increase but only when sea ice is gone by june 1 in the seasonal cycle.
I assert to you that this extra step increase in arctic temperatures will wreak havoc with the currently weakening polar jet and lead to massive heat transport into the arctic of mid-latitude moisture (as well as push the Hadley cell further north and possibly lead to a complete collapse of the Arctic cell into the Ferrell cell (though that might not happen until the arctic reaches a mesothermic state between 2065 and 2100.