Phase question CESM2 ARISE-SAI-1.5 simulations
Stephen Salter
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.
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Subject: [geo] Influence of ENSO on stratospheric sulfur dioxide injection in the CESM2 ARISE-SAI-1.5 simulations
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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
Source: AUTHOREA
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Adrian Hindes
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.