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 2023Submitted to ESS Open Archive 23 Jun 2023Published 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]<mailto:[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/PAXPR05MB80485C9DFF7C694B86F9CF45A72DA%40PAXPR05MB8048.eurprd05.prod.outlook.com.
