There's a short news article in Nature this week - but it's free to read, so please reward their generosity by having a look. The author presumably went over to Hawaii to cover the big CMIP5 workshop that we briefly popped in to. However, the first quote goes to Gavin who steers things neatly in the direction of his workshop that was held the previous week. And Masa Kageyama gets her say too. Poor Jerry Meehl and Karl Taylor are relegated to relative afterthoughts at the bottom of the page. Yes, there is a petabyte of data to look at, and several colleagues are tearing their hair out trying to access it. Apparently the system will be all peachy in a few more months, by which time they will have got it already :-)
To be fair, IMO probably the most exciting thing about the CMIP5 experiments has been the official inclusion of paleoclimate simulations - these have been done before of course, but only as a separate and rather lower-key project. Though this opinion is obviously not shared by many of the modelling groups who haven't actually done the paleo simulations in time for the IPCC report deadlines.
11 comments:
What sort of paleoclimate data would best help constrain your models?
Stuff that is (a) accurate and (b) relates to times when the climate is most closely related to what we expect to see in the future.
Unfortunately there isn't much in either category let alone their intersection! If you could accurately tell me the temperature (map) and CO2 level during the mid-pliocene, that would be very helpful. Thanks awfully.
Hi James,
I presume you've seen this?
Pagani et al. 2009, High Earth-system climate sensitivity determined from Pliocene carbon dioxide concentrations
http://www.nature.com/ngeo/journal/v3/n1/abs/ngeo724.html
Has pCO2 estimates from 'the stable carbon isotope compositions of the di-unsaturated C37 methyl ketone'
Enjoyed your talk in Hawaii, sorry we didn't have a chance to chat.
cheers,
Kevin
Hi James,
I presume you have seen this too:
Lunt, D.J., A.M. Haywood, G.A. Schmidt, U. Salzmann, P.J. Valdes, and H.J. Dowsett, 2010: Earth system sensitivity inferred from Pliocene modelling and data. Nature Geosci., 3, 60-64, doi:10.1038/NGEO706.
Daniel Lunt did his PhD on the Pliocene, so if you haven't it might be worth while getting in touch with him.
James, is it fair to assume that your point is that the mid-Pliocene data, notwithstanding the recent advances in understanding reflected in the noted references, still lacks anything like the precision of data for the HTM and LGM?
Also, AIUI there's an apples and oranges issue with regard to fast feedback sensitivity (the GCMs) versus Earth system sensitivity (the two cited papers).
But I'm largely ignorant about all of this, and would appreciate elucidation.
Yes, I know Dan (from some years back, in fact) and specifically mentioned the pliocene due to this project (see also here) which is associated with pmip.
The problem is, they don't know the boundary conditions with much precision, and the agreement between model results and proxy data is so poor (at least in terms of spatial pattern, the global mean temp change can be fixed by adjusting the CO2) that ISTM that at least one thing must be badly wrong.
Steve, many of the proxies are plant-based, but I don't think soft fruit features particularly - it is things more like pollen types :-) But your prior comment hit the mark :-)
and if someone asks, 'hey, what's the worst that could happen' here's an estimate: http://www.sciencedirect.com/science/article/pii/S0360544210003816
The crepuscular planet. A model for the exhausted atmosphere and hydrosphere
"The Crepuscular Earth presented here is a guess reference model of the planet in which all mineral resources have been extracted and dispersed and fossil fuels have been burnt. It serves as a realistic limit of resources to assess the Earth’s non-renewable exergy capital.
Under such conditions we estimate a state of the atmosphere and hydrosphere using updated fossil fuels stocks (1925 GtC for proven reserves, rising to about 16,224 GtC when including estimated additional reserves) and emissions projections in a simple model of the carbon cycle. We consider the BAU-I scenario as the most likely to occur, corresponding to an atmospheric injection of about 2000 GtC. Accordingly, we propose a crepuscular atmosphere having a carbon dioxide content of 683 ppm, a mean surface temperature of 17 °C (peak carbon dioxide induced warming of 3.7 °C above pre-industrial temperatures), a pressure of 1.021 bar, and a composition in volume basis of 78.8% N2, 20.92% O2, 0.93% Ar, and 0.0015% of trace gases. Considering that oceans account for 97.5% of the whole hydrosphere, the crepuscular hydrosphere is assumed to have the current chemical composition of the oceans at an average temperature of 17 °C."
(I wonder about that ocean chemistry)
Neukum et al. 2010 Southern South America reconstruction seems to be a good one to consider. It is hard to have much confidence in the local temperatures, but it seems to reasonable track the instrument era. Kinda indicates that the Antarctic surface temperatures or off pretty bad though.
Anyway, congrats!
Hank, I think Tim did much better than that, with 6000ppm CO2 (which I also blogged about at the time, it also featured in the "overselling climate change" program).
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