Dear Bala That helps a bit. But even if we do not know the starting point accurately, can we deduce the size of the change we have to make by doing some geoengineering? I thought from Julia Slingo that the problem was 1.7 watts per square metre out of a mean solar input of 340 so we only had to do 0.5%. Stephen
From: Govindasamy Bala <[email protected]> Sent: 22 September 2022 16:26 To: Stephen Salter <[email protected]> Cc: [email protected]; [email protected] Subject: Re: [geo] Climate model bias This email was sent to you by someone outside the University. You should only click on links or attachments if you are certain that the email is genuine and the content is safe. 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]<mailto:[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]<mailto:[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]<mailto:[email protected]>; bala.gov<http://bala.gov>@gmail.com<http://gmail.com> 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/DB7PR05MB56921275E3F6E8B51335E7BBA74E9%40DB7PR05MB5692.eurprd05.prod.outlook.com.
