Impulse Response Functions for Nonlinear, Nonstationary, and Heterogeneous Systems, Estimated by Deconvolution and Demixing of Noisy Time Series

Kirchner, James W.

doi:10.3390/s22093291

“…they considered the nonlinearity of only the "CO 2 chemistry in ocean water, CO 2 fertilization of land biota", i.e., the method is selective in its treatment. Kirchner's approach [76] seems to be a promising alternative. We instead appeal to a well-founded and universally applicable approach [77], one that determines a Volterra series [34,78]:…”

Section: Nonlinearity Of the Carbon Cycle Responsementioning

confidence: 99%

The minimal geoengineering problem concerning the Paris 2015 agreement

Bodai,

Lembo,

Aneesh

et al. 2024

Preprint

0

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There is a palpable shift in mainstream attitude towards geoengineering technologies, seen now as potential parts of a climate policy mix. Still, concerning solar radiation management (SRM) in particular, because of the known and unknown undesirable side-effects of various engineering implementations of theirs, it is important to know what is the minimal intervention that can achieve a certain goal. Such questions lead mathematically to inverse problems. Solving them is feasible only with lightweight models of the climate system, various types of which are nowadays often referred to as emulators – some more accurate than others. Here we develop an emulator using linear and nonlinear response theory and apply it to the minimal SRM problem concerning the Paris 2015 climate agreement, say, with the aim of constraining the global mean surface temperature below a certain limit. Our results suggest that SRM geoengineering, most commonly envisaged as sulfate aerosol injection, will likely have to be part of our climate policy mix, because realistic CO2 abatement effort to come alone cannot restrict global temperatures below the coveted 1.5 ◦C change or below even higher levels of change. Minimal sulfate use for the 1.5 ◦C limit is very likely to dictate immediate and rather abrupt deployment. However, SRM would be no use to achieve such a goal if the geoengineeringfree “asymptotic” temperature is not below the target limit, as it would then need – in the absence of CDR – maintaining SRM “indefinitely”. The latter could be the case even if the temperature response to an anthropogenic CO2 emission pulse is nonmonotonic, and it would be certainly the case if it is monotonic. We show that the model that we use is near the boundary in parameter space between monotonic and nonmonotoninc temperature responses. In the unfortunate case of monotonicity concerning the real Earth system, the only use of SRM would be “buying time” to develop CDR.

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“…they considered the nonlinearity of only the "CO 2 chemistry in ocean water, CO 2 fertilization of land biota", i.e., the method is selective in its treatment. Kirchner's approach [78] seems to be a promising alternative. We instead appeal to a well-founded and universally applicable approach [69], one that determines a Volterra series [35,79]:…”

Section: Nonlinearity Of the Carbon Cycle Responsementioning

confidence: 99%

The minimal geoengineering problem concerning the Paris 2015 agreement

Bodai,

Lembo,

Aneesh

et al. 2024

Preprint

0

View full text Add to dashboard Cite

There is a palpable shift in mainstream attitude towards geoengineering technologies, seen now as potential parts of a climate policy mix. Still, concerning solar radiation management (SRM) in particular, because of the known and unknown undesirable side-effects of various engineering implementations of theirs, it is important to know what is the minimal intervention that can achieve a certain goal. Such questions lead mathematically to inverse problems. Solving them is feasible only with lightweight models of the climate system, various types of which are nowadays often referred to as emulators – some more accurate than others. Here we develop an emulator using linear and nonlinear response theory and apply it to the minimal SRM problem concerning the Paris 2015 climate agreement, say, with the aim of constraining the global mean surface temperature below a certain limit. Our results suggest that SRM geoengineering, most commonly envisaged as sulfate aerosol injection, will likely have to be part of our climate policy mix, because realistic CO2 abatement effort to come alone cannot restrict global temperatures below the coveted 1.5 ◦C change or below even higher levels of change. Minimal sulfate use for the 1.5 ◦C limit is very likely to dictate immediate and rather abrupt deployment. However, SRM would be no use to achieve such a goal if the geoengineeringfree “asymptotic” temperature is not below the target limit, as it would then need – in the absence of CDR – maintaining SRM “indefinitely”. The latter could be the case even if the temperature response to an anthropogenic CO2 emission pulse is nonmonotonic, and it would be certainly the case if it is monotonic. We show that the model that we use is near the boundary in parameter space between monotonic and nonmonotoninc temperature responses. In the unfortunate case of monotonicity concerning the real Earth system, the only use of SRM would be “buying time” to develop CDR.

show abstract

“…they considered the nonlinearity of only the "CO 2 chemistry in ocean water, CO 2 fertilization of land biota", i.e., the method is selective in its treatment. Kirchner's approach [75] seems to be a promising alternative. We instead appeal to a well-founded and universally applicable approach [76], one that determines a Volterra series [77,78]:…”

Section: Nonlinearity Of the Carbon Cycle Responsementioning

confidence: 99%

Inverse problems for climate policy mixes including geoengineering

Bodai,

Lembo,

Aneesh

et al. 2023

Preprint

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There is a palpable shift in mainstream attitude towards geoengineering, seen now as a potential part of a climate policy mix. Still, no-one wants to get on a slippery slope, compounding the risks, and, therefore, we should ask ourselves what is the minimal geoengineering that we can get away with. Such questions lead mathematically to inverse problems. Solving them is feasible only with lightweight models of the climate system, various types of which are nowadays often referred to as emulators – some more accurate than others. Here we develop an emulator using nonlinear response theory and apply it to two paradigmatic inverse problems relevant to climate policy. First, we investigate the attainability of the coveted Paris15 temperature targets. Second, through a simple multi-stable model, we determine what it takes to save the Greenland ice sheet (GrIS) as we know it. Our results suggest, first, that solar radiation management (SRM) geoengineering, most commonly envisaged as sulfate aerosol injection, will likely have to be part of our climate policy mix, because realistic CO2 abatement effort to come alone cannot restrict global temperatures below 1.5 ◦C change or below even higher levels of change. Minimal sulfate use for a threshold target is achieved by immediate and abrupt deployment. Second, we demonstrate also the importance of precisely knowing not only the stable but also the unstable so-called Melancholia states of climate tipping elements, such as the GrIS, as miscalculations can lead to acting too late – whether it is CO2 abatement on the short term or SRM geoengineering deployed in the far future.

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Impulse Response Functions for Nonlinear, Nonstationary, and Heterogeneous Systems, Estimated by Deconvolution and Demixing of Noisy Time Series

Cited by 12 publications

References 22 publications

The minimal geoengineering problem concerning the Paris 2015 agreement

The minimal geoengineering problem concerning the Paris 2015 agreement

The minimal geoengineering problem concerning the Paris 2015 agreement

Inverse problems for climate policy mixes including geoengineering

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