I think the problem of modelling climate change is more fundamental than it is too complex or even how large the biases are.
Our understanding of complex systems like the earth's climate is that they involve feedbacks like the melting of the ice caps that expose darker surfaces that are more adsorbing that increase the warming or the release of methane . In addition complex systems are organized around chaotic attractors and while deterministic one cannot determine how a variable, let's say sea level rise , in one chaotic attractor organization will map to another. So from this perspective modeling the earth's climate within one chaotic attractor has to deal with the inherent nonlinear nature of the climate system but most important is that catastrophic climate change involves the transition from one chaotic attractor to another which while deterministic is not predictable. One the other hand, modeling can help identify the most important feedbacks that could drive the system to reorganize and focus our observations on them to determine whether they show evidences of nonlinear growth. In fact the under prediction of the rate of climate change is in my opinion the result of such nonlinearities which in turn means catastrophic climate change has begun. This is a very important, most important, finding for decision makers. By focusing our discussions instead on detail predictions and comparisons between models we are not only certainly going to fail but we weaken the most important finding that not only is climate change upon us but we are observing that catastrophic climate change has begun. The earths climate has an equivalent of inertia,the rate at a which it reorganizes, called the Liapunov exponent. Our hope is that if we globally organize , mobilize, now we can act faster. Of course that in turn means we have to reorganize the complex human system to address it . As a side comment the above analysis would need to also be applied to the risks of geoengineering efforts because at a high level they all are changing many feedbacks. Reasons like solar variations do occur without catastrophic consequences have to be reconsidered in terms of the current climate already being reorganized. On Thu, Sep 22, 2022 at 8:18 AM Govindasamy Bala <[email protected]> wrote: > I am not at all surprised by the regional bias of this magnitude in the > previous generation of models. The paper says this bias is reduced in CMIP6 > models to about 10 Wm-2. These biases are related to how global models > "represent" cloud properties such as cloud liquid water, liquid cloud > fraction, and total cloud fraction which have biases of about 10-20%. I > would never expect global models with a resolution of about 100 km to > reproduce accurately these subgrid-scale variables. GCMs were not designed > to "simulate" clouds which are "represented" through parameterizations > using various "assumptions". GCMs are designed to only simulate large-scale > (~ 1000 km) features well. Models are only our attempt to explain the real > world and no model exists today in any branch of science that can explain > everything in that branch of science. > > There is nothing here to admire or find fault with modellers. It is just > that the problem is too complex with too many degrees of freedom. In fact, > I am happy we have made unbelievable progress in the last 3-4 decades. It > is a work in progress (like modelling in any branch of science) and I do > not expect an end game anytime soon. > Cheers, > Bala > > On Thu, Sep 22, 2022 at 8:11 PM Stephen Salter <[email protected]> wrote: > >> Hi All >> >> A paper at >> https://link.springer.com/content/pdf/10.1007/s00376-022-2036-z.pdf >> >> says that there are significant biases in simulated cloud physical >> properties over the Southern Ocean. >> >> Section 5 mentions a mean bias of “more than 30 Watts per square metre” >> lots more than I thought was the problem. >> >> However it is not clear, at least to an engineer, whether it means plus >> or minus 30 watts per square metre. >> >> This does not increase my admiration for climate modellers. Please help. >> >> Stephen >> >> *Professor of Engineering Design* >> >> *School of Engineering* >> >> *University of Edinburgh* >> >> *Mayfield Road* >> >> *Edinburgh EH9 3DW* >> >> *Scotland* >> >> *0131 650 5704 or 662 1180* >> >> >> The University of Edinburgh is a charitable body, registered in Scotland, >> with registration number SC005336. Is e buidheann carthannais a th’ ann an >> Oilthigh Dhùn Èideann, clàraichte an Alba, àireamh clàraidh SC005336. >> >> -- >> You received this message because you are subscribed to the Google Groups >> "geoengineering" group. >> To unsubscribe from this group and stop receiving emails from it, send an >> email to [email protected]. >> To view this discussion on the web visit >> https://groups.google.com/d/msgid/geoengineering/DB7PR05MB56927D3815DCF39B23757FA8A74E9%40DB7PR05MB5692.eurprd05.prod.outlook.com >> <https://groups.google.com/d/msgid/geoengineering/DB7PR05MB56927D3815DCF39B23757FA8A74E9%40DB7PR05MB5692.eurprd05.prod.outlook.com?utm_medium=email&utm_source=footer> >> . >> > > > -- > With Best Wishes, > > ------------------------------------------------------------------- > G. Bala > Professor > Center for Atmospheric and Oceanic Sciences > Indian Institute of Science > Bangalore - 560 012 > India > > Tel: +91 80 2293 3428; +91 80 2293 2505 > Fax: +91 80 2360 0865; +91 80 2293 3425 > Email: [email protected]; [email protected] > Google Scholar <https://scholar.google.com/citations?user=eurjQPwAAAAJ> > ------------------------------------------------------------------- > > -- > You received this message because you are subscribed to the Google Groups > "geoengineering" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > To view this discussion on the web visit > https://groups.google.com/d/msgid/geoengineering/CAD7fhVn83ZMtFWHZ%2BdToRZRst_1g7bekeqCJs%3D9ga29Am0PRuw%40mail.gmail.com > <https://groups.google.com/d/msgid/geoengineering/CAD7fhVn83ZMtFWHZ%2BdToRZRst_1g7bekeqCJs%3D9ga29Am0PRuw%40mail.gmail.com?utm_medium=email&utm_source=footer> > . > -- CONFIDENTIAL INFORMATION: This email message and all attachments contain confidential and privileged information that are for the sole use of the intended recipients, which if appropriate applies under the terms of the non-disclosure agreement between the parties. -- You received this message because you are subscribed to the Google Groups "geoengineering" group. 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