Tropical rainforest response to marine sky brightening climate engineering

Muri, Helene; Niemeier, Ulrike; Kristjánsson, Jón Egill

doi:10.1002/2015gl063363

Cited by 26 publications

(20 citation statements)

References 57 publications

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“…However, recent studies such as Eliseev (2012) or Keith et al (2017) suggest that SRM might be understood as a form of carbon dioxide removal (CDR) technique because of its impacts on the global carbon cycle. This statement is also supported by former studies (Eliseev, 2012;Govindasamy et al, 2002;Keller et al, 2014;Lauvset et al, 2017;Matthews & Caldeira, 2007;Muri et al, 2015;Sonntag et al, 2018) which suggest that SRM is likely to strengthen carbon uptake by both ocean and terrestrial ecosystems. This finding is also supported by the modeled response of the carbon cycle to major volcanic eruptions (Brovkin et al, 2010;MacMartin et al, 2016;Rothenberg et al, 2012;Tjiputra & Otterå, 2011).…”

Section: Introductionsupporting

confidence: 75%

“…It results as a consequence to a wide range of responses: from around 19 GtC (Tjiputra et al, 2016) to 251 GtC (Keller et al, 2014) after~80 years of continuous SRM (see Table 1). The persistence of carbon uptake by both land and ocean or the potential rebound effect of the global carbon cycle after stopping SRM remains largely uncertain and poorly assessed in the literature (e.g., Matthews & Caldeira, 2007;Muri et al, 2015).…”

Section: Introductionmentioning

confidence: 99%

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Impact of Solar Radiation Modification on Allowable CO₂ Emissions: What Can We Learn From Multimodel Simulations?

2019

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Solar radiation modification (SRM) is known to strengthen both land and ocean carbon uptake because of its impacts on surface temperature, solar radiation, and other potential drivers of the global carbon cycle. However, the magnitude and timing of the response of both land and ocean carbon uptake to SRM and its consequence on allowable CO2 emissions remain poorly understood. Here we use the results of six Earth system models simulating a continuous stratospheric injection of 5 Tg of sulfur dioxide per year between 2020 and 2069 under the representative concentration pathways 4.5 to investigate the impact of SRM on land and ocean carbon uptake. We find that 50 years of SRM under this protocol increases the allowable CO2 emissions by 40 ± 19 GtC; 85% of this additional uptake of carbon is stored in the land biosphere and 15% in the ocean. This increase in allowable CO2 emissions is however not sustainable after the stoppage of SRM. Earth system models predict a mean release of 8 ± 11 GtC of the carbon back to the atmosphere 20 years after the stoppage which is dominated by large uncertainties in the response of the simulated land carbon cycle to rising temperature and solar radiation. We demonstrate that the time scales of carbon dioxide removal (CDR) potential of SRM are smaller than the time scales of the geological storage assumed in well‐established CDR options. This shows that the CDR potential of SRM should be compared to well‐established CDR options with caution.

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Section: Introductionsupporting

confidence: 75%

Section: Introductionmentioning

confidence: 99%

Impact of Solar Radiation Modification on Allowable CO₂ Emissions: What Can We Learn From Multimodel Simulations?

2019

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“…The size of the injected particles in this study is in the same size range as most previous ESM studies on sea spray climate engineering that simulate the aerosol injection (e.g. Alterskjaer et al, 2012Jones and Haywood, 2012;Korhonen et al, 2010;Muri et al, 2015;and Wang et al, 2011). It should also be mentioned that extensive measurements show that organics contribute substantially to the composition of sea spray aerosol, and in many areas is even the dominant constituent (e.g.…”

Section: Methodsmentioning

confidence: 48%

“…However, more recent studies have included the sea salt injection process and the activation of the injected particles to cloud droplets, thereby taking into account radiative effects of both activated cloud droplets and non-activated particles (Jones and Haywood, 2012;Partanen et al, 2012;. As a result, sea spray climate engineering is now sometimes referred to as marine sky brightening (Muri et al, 2015), as it may include radiative impacts of injected particles both through cloud brightening (the aerosol indirect effect) and due to increased scattering of solar radiation outside clouds (the aerosol direct effect). One of the more recent modelling studies on sea spray climate engineering applied emission patterns to maximize either the direct or the indirect radiative effect of the injected particles, limiting the emission area in both cases to 10 % of the ocean (Jones and Haywood, 2012).…”

Section: Introductionmentioning

confidence: 99%

Marine cloud brightening – as effective without clouds

et al. 2017

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Abstract. Marine cloud brightening through sea spray injection has been proposed as a climate engineering method for avoiding the most severe consequences of global warming. A limitation of most of the previous modelling studies on marine cloud brightening is that they have either considered individual models or only investigated the effects of a specific increase in the number of cloud droplets. Here we present results from coordinated simulations with three Earth system models (ESMs) participating in the Geoengineering Model Intercomparison Project (GeoMIP) G4sea-salt experiment. Injection rates of accumulation-mode sea spray aerosol particles over ocean between 30 • N and 30 • S are set in each model to generate a global-mean effective radiative forcing (ERF) of −2.0 W m −2 at the top of the atmosphere. We find that the injection increases the cloud droplet number concentration in lower layers, reduces the cloud-top effective droplet radius, and increases the cloud optical depth over the injection area. We also find, however, that the global-mean clear-sky ERF by the injected particles is as large as the corresponding total ERF in all three ESMs, indicating a large potential of the aerosol direct effect in regions of low cloudiness. The largest enhancement in ERF due to the presence of clouds occur as expected in the subtropical stratocumulus regions off the west coasts of the American and African continents. However, outside these regions, the ERF is in general equally large in cloudy and clear-sky conditions. These findings suggest a more important role of the aerosol direct effect in sea spray climate engineering than previously thought.

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“…Other issues such as governance, ethical, and societal perception of CE also need to be carefully assessed. There are also other CE techniques, for instance, ocean fertilization, enhanced mineral weathering, and marine cloud brightening [e.g., Ilyina et al , ; Scott et al , ; Keller et al , ; Muri et al , ]. These techniques will have different impacts on the Earth system, and if deployed together, their accumulated impact is unlikely to be linear.…”

Section: Discussionmentioning

confidence: 99%

Impact of idealized future stratospheric aerosol injection on the large‐scale ocean and land carbon cycles

2016

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Using an Earth system model, we simulate stratospheric aerosol injection (SAI) on top of the Representative Concentration Pathways 8.5 future scenario. Our idealized method prescribes aerosol concentration, linearly increasing from 2020 to 2100, and thereafter remaining constant until 2200. In the aggressive scenario, the model projects a cooling trend toward 2100 despite warming that persists in the high latitudes. Following SAI termination in 2100, a rapid global warming of 0.35 K yr−1 is simulated in the subsequent 10 years, and the global mean temperature returns to levels close to the reference state, though roughly 0.5 K cooler. In contrast to earlier findings, we show a weak response in the terrestrial carbon sink during SAI implementation in the 21st century, which we attribute to nitrogen limitation. The SAI increases the land carbon uptake in the temperate forest‐, grassland‐, and shrub‐dominated regions. The resultant lower temperatures lead to a reduction in the heterotrophic respiration rate and increase soil carbon retention. Changes in precipitation patterns are key drivers for variability in vegetation carbon. Upon SAI termination, the level of vegetation carbon storage returns to the reference case, whereas the soil carbon remains high. The ocean absorbs nearly 10% more carbon in the geoengineered simulation than in the reference simulation, leading to a ∼15 ppm lower atmospheric CO2 concentration in 2100. The largest enhancement in uptake occurs in the North Atlantic. In both hemispheres' polar regions, SAI delays the sea ice melting and, consequently, export production remains low. In the deep water of North Atlantic, SAI‐induced circulation changes accelerate the ocean acidification rate and broaden the affected area.

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Tropical rainforest response to marine sky brightening climate engineering

Cited by 26 publications

References 57 publications

Impact of Solar Radiation Modification on Allowable CO₂ Emissions: What Can We Learn From Multimodel Simulations?

Impact of Solar Radiation Modification on Allowable CO₂ Emissions: What Can We Learn From Multimodel Simulations?

Marine cloud brightening – as effective without clouds

Impact of idealized future stratospheric aerosol injection on the large‐scale ocean and land carbon cycles

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Tropical rainforest response to marine sky brightening climate engineering

Cited by 26 publications

References 57 publications

Impact of Solar Radiation Modification on Allowable CO2 Emissions: What Can We Learn From Multimodel Simulations?

Impact of Solar Radiation Modification on Allowable CO2 Emissions: What Can We Learn From Multimodel Simulations?

Marine cloud brightening – as effective without clouds

Impact of idealized future stratospheric aerosol injection on the large‐scale ocean and land carbon cycles

Contact Info

Product

Resources

About

Impact of Solar Radiation Modification on Allowable CO₂ Emissions: What Can We Learn From Multimodel Simulations?

Impact of Solar Radiation Modification on Allowable CO₂ Emissions: What Can We Learn From Multimodel Simulations?