This review from 2018 looks at four different theories explaining the physical climatic causes of ENSO, and might partly answer your question Stephen?
https://academic.oup.com/nsr/article/5/6/813/5126370 All four certainly appear to be proper "oscillations" in the physical/engineering sense, as you can see in the proposed (idealized) equations in that paper. I suppose one could test your theory that direct cooling via SRM of some kind could act as a dampening force, depending on the phase. I'd hesitate to even suggest dampening of ENSO as a hypothetical aim for climate intervention though. ENSO is a pretty important part of the climate system, and despite the negative impacts from El Nino (particularly the enhanced ones we're seeing with global warming), I'm not sure the ecological and societal impacts of dampening it would be justifiable. On Friday, 7 July 2023 at 11:08:30 pm UTC+10 Stephen Salter wrote: > Dear Dr Diao > > > > To engineers the word ‘oscillation’ means the alternating exchange between > two forms of energy, for example between kinetic and potential energy in a > swinging pendulum. Control engineers know that a very small amount of > positive damping (a force opposing velocity) can have a large effect on the > amplitude of oscillations and quite small amounts can kill oscillations > completely. But a small amount of negative damping, a force *in phase* > with velocity, increases amplitudes without limit. > > > > I have asked several eminent climate scientists if the El Niño/La Niña > cycle is an oscillation in the engineering sense or if they are using the > word for a repeating sequence of events with no energy recycling. I was not > able to understand replies and not sure that they could understand my > question. If El Niño events are an engineering-type oscillation we might > be able to moderate them with a very small amount of geoengineering but the > phase of the correction is of vital importance. A cooling treatment in > phase with the temperature change will act like a stiffer spring. This > would increase the frequency of the oscillation and might increase its > amplitude depending on whether it is above or below the natural ‘resonant’ > frequency. But if the cooling treatment depended on the *rate of change* > of temperature then it would behave like a damping. Very small amounts of > damping can kill resonance. Sadly many people do not understand phase. > > > > Stephen Salter > > Ocean Cooling Technology Ltd. > > 27 Blackford Road > > Edinburgh EH9 2DT > > Scotland. > > Jamie Taylor Power for change. > > > > > > > > > > > > > > > > *From:* [email protected] <[email protected]> *On > Behalf Of *Geoengineering News > *Sent:* 07 July 2023 12:49 > *To:* [email protected] > *Subject:* [geo] Influence of ENSO on stratospheric sulfur dioxide > injection in the CESM2 ARISE-SAI-1.5 simulations > > > > *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. > > https://www.authorea.com/doi/full/10.22541/essoar.168748397.70100642 > > > > · *Authors * > > · > > · *Chenrui Diao,* > > · *Elizabeth A. Barnes,* > > · *James Wilson Hurrell* > > > Peer review timeline > > 22 Jun 2023*Submitted to ESS Open Archive * > > *23 Jun 2023**Published in ESS Open Archive* > > > Abstract > > Climate and Earth system models are important tools to assess the benefits > and risks of stratospheric aerosol injection (SAI) relative to those > associated with anthropogenic climate change. A “controller” algorithm has > been used to specify injection amounts of sulfur dioxide in SAI experiments > performed with the Community Earth System Model (CESM). The experiments are > designed to maintain specific temperature targets, such as limiting global > mean temperature to 1.5ºC above the pre-industrial level. However, the > influence of natural climate variability on the injection amount has not > been extensively documented. Our study reveals that more than 70% of the > year-to-year variation in the total injection amount (excluding the > long-term trend) in CESM SAI experiments is attributed to the El > Niño-Southern Oscillation (ENSO). A simplified statistical model further > suggests that the intrinsic, lagged response of the controller to the > climate can increase the variance of global mean temperature in the model > simulations. > > *Cite as: *Chenrui Diao, Elizabeth A. Barnes, James Wilson > Hurrell. Influence of ENSO on stratospheric sulfur dioxide injection in the > CESM2 ARISE-SAI-1.5 simulations. *Authorea.* June 23, 2023. > *DOI: 10.22541/essoar.168748397.70100642/v1 > <https://doi.org/10.22541/essoar.168748397.70100642/v1>* > > *Source: AUTHOREA* > > -- > 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/CAHJsh99FhpDKGHOWL32M8aai3BLSxyfRpBTR_e2_FFbpsvZr1Q%40mail.gmail.com > > <https://groups.google.com/d/msgid/geoengineering/CAHJsh99FhpDKGHOWL32M8aai3BLSxyfRpBTR_e2_FFbpsvZr1Q%40mail.gmail.com?utm_medium=email&utm_source=footer> > . > 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/ecbc57e9-29c3-4b2b-a195-d38d6dc389f9n%40googlegroups.com.
