---
tags: Science, Papers
lang: en-GB
---

# State-of-the-art: volcanic impact of Earth's climate

[](https://hackmd.io/j4L-EIhRQqGdl5KmiIZ-_w)
[](https://github.com/engeir/hack-md-notes/blob/main/volcano-papers.md)

> **_Overview of papers._** [color=#907bf7]

:::info
Potential simulations from MIPs (although I haven't found any realizations of them yet)
are: '**[volc-cluster-ctrl]**' (VolMIP tier 2), '**[volc-cluster-mill]**' (VolMIP tier
3) and '**[past1000-volc-cluster]**' (PMIP tier 3, this includes all external drivers).
(Full VolMIP tier overview can be found
[here](https://view.es-doc.org/?renderMethod=id&project=cmip6&id=b2368e99-26ae-4bf5-915e-504a702b1f4f&version=1&client=esdoc-search).)
:::

## Literature

### 1998 — Lindzen, Giannitsis: On the climatic implications of volcanic cooling

> DOI:
> [10.1029/98JD00125](https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/98JD00125)

- Uses 3-box EBM to look at the response to volcanoes under different sensitivities by
adjusting the coupling between ocean-atmosphere (high sensitivity → weak coupling.)
- In more sensitive climates, the ocean plays a more important role in leading the
system back to equilibrium.
- Sensitivity matter less in the first year or two, then larger sensitivity gives a
slower recovery to equilibrium than the weak sensitivity case.

### 2005 — Hansen et al.: Efficacy of climate forcings

> DOI: [10.1029/2005JD005776](https://doi.org/10.1029/2005JD005776)

- Wishes to compare the efficacy of different climate forcings, where ideally they all
have the same efficacy of one
- The efficacy is defined as the global temperature response per unit forcing relative
to the response to CO2 forcing

### 2005 — Jones et al.: An AOGCM simulation of the climate response to a volcanic super-eruption

> DOI: [10.1007/s00382-005-0066-8](https://doi.org/10.1007/s00382-005-0066-8)

- The first coupled model simulation of a generic volcanic super-eruption
- Examined the response to a maximum stratospheric loading of $1.4\,\mathrm{Gt}$
($=1400\,\mathrm{Mt}=1400\,\mathrm{Tg}$) of sulphate aerosols
- AOD of $\sim 15$, similar in size to Toba 72ky ago (two orders of magnitude larger
than Mount Pinatubo, i.e., Pinatubo volcanic aerosol times 100).
- Maximum radiation TOA imbalance of $-60\,\mathrm{Wm^{-2}}$
- A maximum temperature fall of $10.7\,\mathrm{K}$, $9.4\,\mathrm{K}$ for the maximum
annual mean
- Albedo increase from $0.3$ to $0.7$
- They used HadCM3, with the optical depth values input into the model as monthly
quarterspheric values
- Within the model, the sulphuric acid mass was calculated and distributed evenly above
the model tropopause
- Since they use aerosol concentrations of $100\times$Pinatubo, any non-linear chemical
processes that may occur will not be included
- For example, the highest level in HadCM3 is $5\,\mathrm{hPa}$ ($\sim
30\,\mathrm{km}$), but a plume from a super-eruption could possibly reach above
$40\,\mathrm{km}$
- ==Encourage more work on expanding our knowledge of past volcanic eruptions and their
impact on the environment==

### 2008 — Gao et al.: Volcanic forcing of climate over the past 1500 years: An improved ice core-based index for climate models

> DOI: [10.1029/2008JD010239](https://doi.org/10.1029/2008JD010239)

- Gives an updated time series of the last 1500 years of volcanic forcing
- The output is made to be _total stratospheric volcanic sulphate aerosol injection_, in
units of Tg, Terra gram
- ==Converting from $\mathrm{Tg}$ to $\mathrm{W/m^2}$, i.e., what is usually used as
forcing==: (paragraph 17)
1. Divide the loading by $1.5\times 10^{14}\,\mathrm{Tg}$ to obtain optical depth
2. Multiply optical depth by $20$ to obtain the radiative forcing in $\mathrm{W/m^2}$

### 2009 — Timmreck et al.: Limited temperature response to the very large AD 1258 volcanic eruption

> DOI: [10.1029/2009GL040083](https://doi.org/10.1029/2009GL040083)

- ==Examines the climate response as a function of aerosol size==
- The 1258 eruption had ten times as much stratospheric sulphate load as Pinatubo, but
the temperature response does not compare
- Larger particles scatter less visible light and absorb more efficiently in the near-
and far-infrared
- Uses the MPI-M model
- Forcing is AOD at 550 nm specified on four equal-area latitude bands
- The find no significant difference in the greenhouse effect, but the albedo effect is
strongly modulated
- Larger particles are removed more quickly (due to gravity), but an opposing effect
that might occur is that OH radicals are depleted and the conversion rate from SO~2~
to sulphuric acid vapour is reduced, which would impede (get in the way of; hinder)
the growth of aerosol particles and prolong their atmospheric lifetime

### 2010 — Timmreck et al.: Aerosol size confines climate response to volcanic super‐eruptions

> DOI: [10.1029/2010GL045464](https://doi.org/10.1029/2010GL045464)

**Take away:** Global mean temperature anomalies (from YTT) are three times weaker than
previously suggested.

- Two more recent simulations with coupled atmosphere-ocean models calculated a decade
of severe cooling of up to $-10\,\mathrm{K}$ (global mean) for a Toba simulation
comparable to 100 times Pinatubo.
- _For estimating the climatic consequences of large volcanic eruptions, the
stratospheric sulphur (S) emission of the erupting magma is of central importance._
(Estimates vary with more than one order of magnitude.)
- Immediately after the eruption:
1. SO~2~ is oxidized into condensable H~2~SO~4~ vapour (SO~2~ oxidation is delayed
when compared with the evolution after the much weaker 1991 Pinatubo eruption due
to the limiting factor of OH-abundance)
2. After the maximum size is reached (about one year after the eruption), rapid
sedimentation of large aerosol particles occurs, so AOD is already at background
levels by year four (smaller than the lifetime given by Bekki of ten years)
- In all ensemble members, maximum cooling is much smaller and of considerably shorter
duration than reported in former model studies. Previous studies have:
- $-3.5\,\mathrm{K}$ cooling but a prolonged cooling response
- $-10\,\mathrm{K}$ cooling but back to normal well within a decade
- Advection of mild moist air from the Atlantic overrides the effect of radiative
cooling in this region (northern Eurasia), something that has been observed after most
historic volcanic eruptions
- A more complete treatment of stratospheric aerosol formation and growth lead to much
weaker radiative forcing due to larger particle sizes and faster removal rate
- The global distribution of temperature anomalies is highly dependent on the initial
state of the Pacific

### 2012 — Rypdal, K., Global temperature response to radiative forcing: Solar cycle versus volcanic eruptions

> DOI: [10.1029/2011JD017283](https://doi.org/10.1029/2011JD017283)

**Take away:** An overview of simple EBMs and how well-suited they are to represent the
GMST from 1880 to 2010.

- $-\lambda^{-1}\Delta T$ (he uses $\lambda=S_\mathrm{eq}$) represents the change of
flux of infrared radiation in response to the temperature change $\Delta T$
- The parameter $\lambda$ measures how much the equilibrium temperature $\Delta
T_\mathrm{eq}$ changes in response to a forcing perturbation $\Delta F$, and is
therefore called the climate sensitivity
- _Explanation of "warming in the pipeline"_
- _Why the temperature response to volcanic eruptions represent a useful tool to
determine the sensitivity and time constant_
- The mismatch in spectral index as well as in amplitude, clearly indicates that the
climate noise is internally generated and not a response to fluctuations in solar
forcing
- Inferring sensitivity and time constants from MLE is misleading since it assumes a
model in which white noise is used to represent internal variability, but the
fluctuations in the climate system is not white noise
- The MLE approach is futile (with some restrictions)
- (In support of the scale-free response.) Before dismissing the idea of a scale-free
response one should not forget that eq.(1) is derived without taking into account slow
feedback. The temperature that was in equilibrium with the forcing a few decades ago
is not in equilibrium with the same forcing today. A measure of climate sensitivity as
a single parameter may make little sense

### 2015 — Johansson et al.: Equilibrium climate sensitivity in light of observations over the warming hiatus

> DOI: [10.1038/nclimate2573](https://doi.org/10.1038/nclimate2573)

- The warming hiatus (1980s and 90s) is primarily attributable to El Niño/Southern
Oscillation-related variability and reduced solar forcing.
- We suggest that it is too early to conclude that the hiatus has had any particular
impact on estimates of ECS.

### 2016 — Toohey et al.: Climatic and societal impacts of a volcanic double event at the dawn of the Middle Ages

> DOI: [10.1007/s10584-016-1648-7](https://doi.org/10.1007/s10584-016-1648-7)

- Uses the MAECHAM5-HAM model, which takes emissions from AEROCOM(?) (see
[this paper](https://acp.copernicus.org/articles/5/1125/2005/acp-5-1125-2005.pdf),
[Timmreck et al. (2010)](https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2010GL045464)
also use that emission source). Combines this with MPI-ESM
([source](https://agupubs.onlinelibrary.wiley.com/doi/full/10.1002/jame.20038)).
- Might have some interesting data: double volcano event in 536 and 540 CE.
- Single events were not large compared to the last about 2000 years, but their combined
response was the largest within that same time period.
- Found that the impact of the first extra-tropical eruption was not minor compared to
the second tropical eruption, opposite to most other studies.
- Found indications of prolonged impacts of the eruptions on decade-length scales in
Arctic sea-ice production.

### 2018 — Marshall et al.: Multi-model comparison of the volcanic sulfate deposition from the 1815 eruption of Mt. Tambora

> DOI: [10.5194/acp-18-2307-2018](https://doi.org/10.5194/acp-18-2307-2018)

- CESM1(WACCM) starts spreading at a later time, and the sulfate stays for longer
- Aerosol formation and growth are simulated through parametrizations of nucleation,
condensation and coagulation
- Modal aerosol schemes represent aerosol particle size distribution by several
log-normal modes
- Transport of stratospheric aerosols happens through sedimentation and large-scale
circulation by the Brewer-Dobson circulation
- The QBO is nudged (by CESM1(WACCM))
- Dry deposition schemes are resistance-based and wet deposition is parametrized based
on model precipitation and convective processes
- Aerosol removal is calculated via first-order loss processes representing in-cloud and
below-cloud scavenging
- CESM1(WACCM) includes interactive hydroxyl radical (OH) chemistry, allowing OH
concentrations to evolve throughout the simulations (MAECHAM5-HAM does not have this,
which is why SO2 levels peak earlier)
- The Brewer-Dobson circulation is stronger during winter, therefore the transport to
the SH of sulfate aerosols is stronger than the transport to the NH
- In CESM1(WACCM) the poleward transport of volcanic aerosol may be too weak or
midlatitude deposition too strong
- CESM1(WACCM) has the strongest polar jets, which may affect the polar sulfate
deposition, but it appears to be a combination of factors
- Scavenging and deposition parametrizations are highly uncertain, especially as the
eruptions become larger

### 2019 — Yang et al.: Climate Impacts From Large Volcanic Eruptions in a High-Resolution Climate Model: The importance of Forcing Structure

> DOI: [10.1029/2019GL082367](https://doi.org/10.1029/2019GL082367)

**Take away:** Different sensitivity from different volcanic forcings, spatial structure
matter

Introduction

- Volcanoes impact ENSO, ITCZ (intertropical convergence zone) tropical cyclones, NAO
(North Atlantic Oscillation) and more, but has low signal-to-noise ratio or depend on
initial state, perhaps even model dependent.
- FLOR coupled climate model, $50\,\mathrm{km}$ horizontal resolution.

Questions

- Temperature and precipitation response to different eruptions ((a)symmetric)
- What is the response to TC activity?
- Proportional climate response?

Results and discussion

- Pinatubo reduces precipitation over the tropics
- Asymmetric reduces where the load is, enhances on the opposite hemisphere. Global mean
somewhat enhanced.
- TAS in high-load hemispheres are comparable to Pinatubo
- Stronger impact on precipitation and TC than Pinatubo
- ==Transient climate sensitivity is not proportional:== largest from Santa Maria (NH),
identical from Pinatubo (both) and Agung (SH).
- Usually, it is assumed that weaker eruptions have a weaker impact, this demonstrates
the opposite can be the case.
- This highlight ==importance of spatial structures==.
- Crucial to obtaining an accurate reconstruction of volcanic aerosol radiative property
spatial structure.

### 2019 — Marshall et al.: Exploring How Eruption Source Parameters Affect Volcanic Radiative Forcing Using Statistical Emulation

> DOI: [10.1029/2018JD028675](https://doi.org/10.1029/2018JD028675)

**Take away:** SO~2~ and latitude of eruption matter, while the injection height is
relatively unimportant.

- Uses the interactive stratospheric aerosol model UM-UKCA; it treats the full lifecycle
of stratospheric aerosol particles
- They use parameters from a space-filling "maxmin" Latin hypercube
- The $e$-folding time: based on a linear fit starting one month after the peak until it
reaches $10\%$ of the peak burden
- Integrated values: integrated over $38$ months (end of simulation); the sum of the
monthly mean anomalies in global mean SAOD and net radiative forcing
- The $e$-folding time is dependent on latitude (BDC), SO~2~ emission magnitude
(particle growth and increased sedimentation), and weakly on SO~2~ injection height
(longer air residence time)
- Also discusses "phases" of the $e$-folding time that changes the average, i.e., more
time scales exist

### 2019 — Richardson et al.: Efficacy of Climate Forcings in PDRMIP Models

> DOI: [10.1029/2019JD030581](https://doi.org/10.1029/2019JD030581)

**Summary for ECS paragraph:** Richardson compared many different sims setups, where
5xSO4 was one of them, that is, 5 times sulfate aerosol concentrations or emissions, as
a step function. IRF give differing efficacies (as expected), but for ERF (use this)
efficacies are closer to unity. MAYBE YES.

**Take away:** Forcing behaves similarly across agents

- No evidence that the geographical location of sulfate aerosol affects its efficacy
- Quantifying forcing efficacies and understanding how robust they are across different
models are of substantial importance
- Compares six different ways of estimating forcing from different forcing agents, and
evaluates their appropriateness based on the efficacies, which should be unity.
$\mathrm{ERF}_\mathrm{sst}$ comes out as optimal (effective radiative forcing from
fixed sea-surface temperature).
- ==Uses large aerosol perturbations, and it is assumed that the temperature response
scales linearly with forcing strengths. Calls for further studies to explore that.==

### 2019 — Zanchettin et al.: Clarifying the Relative Role of Forcing Uncertainties and Initial-Condition Unknowns in Spreading the Climate Response to Volcanic Eruptions

> DOI: [10.1029/2018GL081018](https://doi.org/10.1029/2018GL081018)

- Want to answer the question "Is constraining the magnitude of forcing estimates more
important than constraining initial conditions to be able to accurately simulate the
climate response to a specific volcanic eruption?"
- Initial conditions can dominate the global mean temperature response from volcanic
eruptions compared to different realistic choices on its magnitude
- A big summer-winter asymmetry in the ensemble spread of posteruption anomalies,
reflecting a prominent contribution of internal dynamics to the winter response

### 2020 — Gregory et al.: How accurately can the climate sensitivity to CO~2~ be estimated from historical climate change?

> DOI: [10.1007/s00382-019-04991-y](https://doi.org/10.1007/s00382-019-04991-y)

- Volcanic forcing in the mean of CMIP5 is 80% of the AR5 estimate, which is attributed
to rapid cloud adjustments not included in the AR5 estimate
- For volcanic aerosol, $\alpha$ _may_ be larger than for CO~2~ (EffCS smaller,
efficacy, less than unity), since regression of $R=F-N$ (annual mean) against $T$ is
much steeper.
- EffCS is higher when volcanic forcing is relatively less important (see a similar
trend when volcanoes are not present, 1945-1975, and when CO~2~ is dominant,
1975–2005).
- CMIP5 AOGCMs are not realistic in their response to volcanic forcing. In the real
world, instead of causing a rapid cooling of $T$, volcanoes have the effect of
"sucking" heat from the ocean beneath.

### 2020 — Marshall et al.: Large Variations in Volcanic Aerosol Forcing Efficiency Due to Eruption Source Parameters and Rapid Adjustments

> DOI: [10.1029/2020GL090241](https://doi.org/10.1029/2020GL090241)

**Take away:** The single scaling of $25\,\mathrm{W/m^2}$ used by IPCC is too crude.
They find radiative forcing to be about $20\%$ weaker than that reported by the IPCC
based on Pinatubo only.

- A scaling factor of $25$ is too much
- They also note that there is a dependence on year-after-eruption, where the first year
has the weakest forcing per SAOD, before it increases in years two and three
- SAOD is weaker in year 1 compared to year 2 (and 3), stronger for tropical than
extratropical eruptions, and is stronger for winter than summer eruptions

### 2021 — Pauling et al.: Robust Inter-Hemispheric Asymmetry in the Response to Symmetric Volcanic Forcing in Model Large Ensembles

> DOI: [10.1029/2021GL092558](https://doi.org/10.1029/2021GL092558)

**Take away:** Despite the different nature of the forcings, CO~2~ and an almost
symmetrical Pinatubo-like volcanic eruption both give a similar asymmetrical response in
the climate system

Introduction

- Makes use of CMIP6 to evaluate high-latitude climate response during large eruptions
- Simulations are forced with historical GHG, ozone, solar and aerosol forcing.

Results and discussion

- Sea ice volume in CESM2 is much greater and persists longer than in the other models
- Symmetric forcing (Pinatubo) gives asymmetry in zonal-mean TAS
- Some ensemble members warm at high latitudes
- ==Robust feature:== The inter-hemispheric asymmetry in the temperature response of the
climate system response to approximately hemispherically symmetric volcanic forcing
- ==Despite the dissimilar physical nature of the forcings, the same asymmetric fast
response to CO2 is what they find here for symmetric volcanic forcing==

### 2022 — Salvi et al.: Interpreting differences in radiative feedbacks from aerosols versus greenhouse gases

> DOI: [10.1029/2022GL097766](https://doi.org/10.1029/2022GL097766)

**Summary for ECS paragraph:** Salvi ran simulations of historical aerosols, but this
does not mean natural volcanic aerosols it seems. Different sensitivity between forcing
agents, but a bit smaller sample size than Richardson. MAYBE NO.

**Take away:** Aerosols produce more amplifying climate feedback (greater climate
sensitivity) than CO~2~ does, in contrast to Richardson (2019)

- ==Not a consensus on whether $\alpha$ (climate feedback parameter — $N=F-\alpha T$)
depends on the different forcing agents.==
- Differences in radiative feedback across forcing agents may be explained in terms of
different tropospheric stability responses and their impact on cloud and lapse-rate
feedback.
- Higher tropospheric stability → low boundary-layer clouds over marine regions
- Low clouds reflect solar → cooling effect on radiation
- Expect a positive correlation between net $\alpha$ and the stability response per unit
global warming ($\mathrm{d}S/\mathrm{d}T$)
- ==Finally calls for further work to settle the disagreement between their and the
Richardson (2019) results (i.e., that aerosols give greater sensitivity than GHG)==
(also in contrast to Pauling (2021) it seems?)

### 2022 — Chen et al.: Modulating and Resetting Impacts of Different Volcanic Eruptions on North Atlantic SST Variations

> DOI: [10.1029/2021JD036246](https://doi.org/10.1029/2021JD036246)

- Volcanic eruptions a pacemaker for the phase transition of SST
- From Mann et al. (2021), volcanoes are the main driver of 40- to 60-year variability
of SST over NA
- Discusses volcanic impact on the deep ocean: Strong volcanoes (at least more than
$50\,\mathrm{Tg}$, but should be more than $100\,\mathrm{Tg}$) can strengthen the AMOC
which subsequently cools the deep ocean

### 2022 — Lin et al.: Magnitude frequency and climate forcing of global volcanism during the last glacial period as seen in Greenland and Antarctic ice cores (60-9 ka)

> DOI: [10.5194/cp-18-485-2022](https://doi.org/10.5194/cp-18-485-2022)

- Frequency is investigated
- End up with:

| | Absolute number of eruptions | --- | Eruptions per millennium | --- |
| ------------------------------------------- | :--------------------------: | :--------------------------------------------------: | :----------------------: | :--------------------------------------------------: |
| | $0$--$2.5\,\mathrm{ka}$ | $9$--$16.5\,\mathrm{ka}$ & $24.5$--$60\,\mathrm{ka}$ | $0$--$2.5\,\mathrm{ka}$ | $9$--$16.5\,\mathrm{ka}$ & $24.5$--$60\,\mathrm{ka}$ |
| $<-13.2\,\mathrm{Wm^{-2}}$ (Oruanui, Taupo) | 0 | 3 | 0 | 0.07 |
| $<-9.5\,\mathrm{Wm^{-2}}$ (EU 426 BCE) | 1 | 25 | 0.4 | 0.58 |
| $<-6.5\,\mathrm{Wm^{-2}}$ (Tambora) | 6 | 69 | 2.4 | 1.60 |

Note that the investigated period of the last glacial and the early Holocene covers
some $43\,\mathrm{kyr}$ ($60$--$9\,\mathrm{ka}$ minus the section of no identified
bipolar eruptions at $24.5$ to $16.5\,\mathrm{ka}$).

### 2022 - Günther et al.: Climate Feedback to Stratospheric Aerosol Forcing: The Key Role of the Pattern Effect

> DOI: [10.1175/JCLI-D-22-0306.1](https://doi.org/10.1175/JCLI-D-22-0306.1)

- **Overall feedback is close to one, but this is because of compensation: early, the
feedback is strong, while later the feedback is weak**

### 2023 - Pauling et al.: The climate response to the Mt. Pinatubo eruption does not constrain climate sensitivity

> DOI: [10.1029/2023GL102946](https://doi.org/10.1029/2023GL102946)

**Summary for ECS paragraph:** Pauling looks at Bender results, among others, and
conclude we cannot constrain ESC from volcanoes (even if there is a correspondence, Mt
Pinatubo has too small S-N ratio). HARD NO.

## Original papers

### 2002 — Soden et al.: Global Cooling After the Eruption of Mount Pinatubo: A Test of Climate Feedback by Water Vapor

> DOI:
> [10.1126/science.296.5568.727](https://www.science.org/doi/10.1126/science.296.5568.727)

Water vapour introduction

- They show: without strong _positive_ feedback from water-vapour, the model is unable
to reproduce the observed cooling.
- Hence, climate models heavily rely on water-vapour feedback.
- WV is the dominant greenhouse gas and provides the largest feedback for amplifying
climate change.
- Increases with temperature → doubles the sensitivity of temperature to an increase in
anthropogenic greenhouse gases.
- If the actual feedback is weaker, uncertainty would be smaller.
- **How well-represented is it in climate models?** (Refs. 6 & 7)

Role of volcanoes

- Volcanoes provide valuable observations of the system's response (transient) to
external radiative forcing. Aerosols spread largely in the lower stratosphere.
- Effective at scattering sunlight, bad at absorbing long wave radiation.
- Mount Pinatubo cooled the lower troposphere → reduction in global water vapour
concentration.

Simulations

- Uses a GCM, mixed-layer ocean.
- Starting 5 months before the eruption, and lasting 5 years.
- Three pairs with control & Mount Pinatubo (observed zonal mean distribution of
aerosols).
- Data indicate peak 18 months after the eruption (0.5 K cooling).

### 2005 — Wigley et al.: Effect of climate sensitivity on the response to volcanic forcing

> DOI:
> [10.1029/2004JD005557](https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2004JD005557)

**Summary for ECS paragraph:** Wigley used an ensemble of historic volcanoes, 1890 to
2000, output of AOGCMs, and ran an upwelling diffusion EBM to emulate an AOGCM. Assume
sensitivity dependence, if any exist, is small, and thus that one can constrain ECS with
volcanoes. End up with estimates of ECS. YES.

Introduction

- Wants to: obtain an improved estimate of the underlying response of 20th-century
global mean temperature to volcanic forcing.
- Also, use simulations to reduce internally generated noise (16 coupled AOGCM)
- **Maximum cooling depends on sensitivity raised to power 0.37.**
- Temperature relaxes back with $e$-folding time of 29--43 months.
- Pinatubo requires sensitivity above the $1.5^\circ\text{C}$ (lower bound). None of the
eruptions rule out sensitivity above $4.5^\circ$C.
- Problems when comparing modelled and observed effects are
1. Poor forcing precision at earlier times
2. Signal-to-noise ratio. The response is quick and decays after a relatively short
time
3. Forcing events lasting shorter than 5 years are less sensitive to $\Delta T2x$ than
longer ones.
4. Sensitivity may depend on the nature of the forcing and the spatial distribution.
- [LG98](https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/98JD00125) note that
response to consecutive eruptions has closer dependence with $\Delta T2x$.
- 3-box EBM, $400\,$m deep, diffusive ocean

Simulations

- Good agreement between MAGICC (model) and AOGCM.
- They quantified relaxation timescales by fitting exponential decay curves.

### 2005 — Yokohata et al.: Climate response to volcanic forcing: Validation of climate sensitivity of a coupled atmosphere-ocean general circulation model

> DOI: [10.1029/2005GL023542](https://doi.org/10.1029/2005GL023542)

- Simulations of volcanic cooling using a GCM have not been considered to date (2005) as
a test of climate sensitivity.
- Here, Mt. Pinatubo is simulated with low- and high-sensitivity GCMs (differ in how
they treat clouds).

### 2006 — Douglass et al.: Thermocline flux exchange during the Pinatubo event

> DOI: [10.1029/2006GL026355](https://doi.org/10.1029/2006GL026355)

- Uses EBM with coupling between the mixed layer and the thermocline, exponential, exact
solutions, exponential, exact solutions
- Get a short response time of $\tau=4.4\mathrm{months}$
- _Pinatubo: $0.5^{\circ}\mathrm{C}$ cooling and $4\,\mathrm{W/m^2}$ decrease in
outgoing longwave radiation_
- $7.6$ months; peak of aerosol forcing

### 2007 — Boer et al.: Inferring climate sensitivity from volcanic events

> DOI: [10.1007/s00382-006-0193-x](https://doi.org/10.1007/s00382-006-0193-x)

**Summary for ECS paragraph:** Boer did simulationss using volcano-like eruptions:
changed solar constant according to en exponential. This also means complete
"ash-cover". Sensitivity need not be constant, so sensitivity for short timescale
volcano-perturbations is different from ECS. Claims it might be possible to infer
climate sensitivity if the forcing and heat storage is known (but not temperature
alone). MAYBE WITH HIGH PRECISION.

- For volcano-like forcing the global mean surface temperature responses of the models
are very similar, despite their differing equilibrium climate sensitivities,
indicating that climate sensitivity cannot be inferred from the temperature record
alone even if the forcing is known.
- The overall conclusion is that climate sensitivity cannot be inferred directly from
the global average temperature response to volcano-like forcing even if the forcing is
known. An independent knowledge of the heat penetration into the deep ocean is
required.
- One possibility is that the real climate system operates like the slab ocean model
(rather than the full ocean model).
- The experiments support the possibility of inferring the climate sensitivity of the
real system by studying the impact of volcanoes provided that both the forcing and the
heat storage in the system are known with sufficient accuracy.

### 2010 — Bender et al.: Response to the eruption of Mount Pinatubo in relation to climate sensitivity in the CMIP3 models

> DOI: [10.1007/s00382-010-0777-3](https://doi.org/10.1007/s00382-010-0777-3)

**Summary for ECS paragraph:** Bender uses Mt. Pinatubo to link to ECS. THERE IS
CORRESPONDANCE, SO YES WE CAN INFER ECS FROM VOLCANOES.

### 2012 — Lovejoy and Schertzer: Stochastic and scaling climate sensitivities: Solar, volcanic, and orbital forcings

> DOI: [10.1029/2012GL051871](https://doi.org/10.1029/2012GL051871)

### 2014 — Merlis et al.: Constraining Transient Climate Sensitivity Using Coupled Climate Model Simulations of Volcanic Eruptions

> DOI: [10.1175/JCLI-D-14-00214.1](https://doi.org/10.1175/JCLI-D-14-00214.1)

**Summary for ECS paragraph:** Merlis ran an ensemble of SAOD forced Pinatubo eruptions
and compared with 2xCO2 and 0.5xCo2. Strong focus on volcanoes and how they might
constrain TCR (and ECS).

### 2014 — Arfeuille et al.: Volcanic forcing for climate modelling: a new microphysics-based data set covering years 1600-present

> DOI: [10.5194/cp-10-359-2014](https://doi.org/10.5194/cp-10-359-2014)

- NH extra-tropical eruptions tend to exhibit smaller effective radii than tropical
eruption for a given SO~2~ erupted mass

### 2015 — Sigl et al.: Timing and climate forcing of volcanic eruptions for the past 2,500 years

> DOI: [10.1038/nature14565](https://doi.org/10.1038/nature14565)

- The findings indicate that eruption-induced climate anomalies following large tropical
eruptions may last longer than is indicated in many climate simulations (<3–5 years).
- They suggest that potential positive feedback initiated after large tropical eruptions
(for example, sea-ice feedback) may not be adequately represented in climate
simulations.

### 2016 — Ollila: Climate Sensitivity Parameter in the Test of the Mount Pinatubo Eruption

> DOI: [10.9734/PSIJ/2016/23242](https://doi.org/10.9734/PSIJ/2016/23242)

**Summary for ECS paragraph:** Ollila looked at Pinatubo in a dynamical model, so not a
GCM. Hmm, not sure what to conclude from this.

- Time constants for the ocean of $2.74$ months and the land of $1.04$ months are
accurate and applicable in the dynamic analysis.

### 2016 — Marvel et al.: Implications for climate sensitivity from the response to individual forcings

> DOI: [10.1038/nclimate2888](https://doi.org/10.1038/nclimate2888)

**Summary for ECS paragraph:** Marvel used simulations where many kinds were
represented, among others idealized volcano simulations. Talk about ERF as opposed to
IRF... When calculating ESC, do not use the efficacy of \ce{CO2}: individual forcings
produce different efficacies (this lead to better consistency to previous constraining
studies).

- Forcing that projects more strongly on the Northern Hemisphere are more effective at
changing temperatures than CO~2~.
- =='historical-misc' archive includes 1850--2005 runs of single forcings, including
volcanic forcing.==
- The use of effective (rather than instantaneous) radiative forcing may render the
sensitivities from GHG-only and historical simulations more directly comparable.

### 2016 — Lehner et al.: The importance of ENSO phase during volcanic eruptions for detection and attribution

> DOI: [10.1002/2016GL067935](https://doi.org/10.1002/2016GL067935)

- CMIP5 indicates that models overestimate the magnitude of the global temperature
response to volcanic eruptions (sampling issue, eruptions coincided with El Niño
events).
- When they explicitly account for the effects of internal variability, the GMST
response to volcanic eruptions is consistent, within uncertainties, between models and
observations. This holds in particular for the coincidence of El Niño events (be it by
chance or due to an eruption triggering an El Niño event).
- **The subject of ongoing research:** how (and if) Southern Annular Mode is confounded
by superposition of eruptions and El Niño events.

### 2016 — Gregory et al.: Small global-mean cooling due to volcanic radiative forcing

> DOI: [10.1007/s00382-016-3055-1](https://doi.org/10.1007/s00382-016-3055-1)
>
> Answer: what is the main goal, why do they not include annual mean temperature against
> forcing? They look for different reasons why the cooling is smaller than expected. So,
> maybe it would be a bit counter-intuitive to look at total temperature against
> forcing? No wait, they actually do. Fig. 6. They get from volcanoes $F=-2.7\pm0.1\\,
> \mathrm{W/m^2}$, while the abrupt 4xCO2 give $F=7.7\\,\mathrm{W/m^2}$.

- Relation between aerosol optical depth and radiative forcing (in
$\text{W}\text{m}^{-2}$) show a linear trend (fig. 4)
- TCRP - Transient Climate Response Parameter: The increase in global-mean temperature
per unit increase in radiative force during time-dependent climate change
- Their zero layer model overestimates the sudden cooling in the AOGCMs from short-lived
large negative forcing from volcanic eruptions. Assumed to be due to the zero-layer
model neglecting upper-layer heat capacity. **Thus, the difference in CO2 vs. volcano
forcing is not the sign, but the timescale**. The TCRP and the zero-layer model is not
applicable.
- Two common issues: the forcing $F$ due to volcanoes is not diagnosed (i.e., no fixed
SST run is done), and $\alpha$ might not be the same as it is for $\mathrm{CO_2}$
- When analysing ocean heat uptake they use a step model which relies on the assumption
that the response of the system depends linearly on the forcing
- Regression of $F$ against AOD gives a slope of $-24.6\pm0.2$ for AR5
- Confirms that the smaller climate sensitivity to volcanic forcing during the
historical period than for elevated $\mathrm{CO_2}$ is also a reason for the
overestimation of volcanic cooling by the TCRP in HadCM3, although less important than
ocean heat uptake and volcanic forcing (could be due to difference in forcing nature
or that the sensitivity depends on $\mathrm{CO_2}$ concentration)
- A large ensemble is needed to precisely evaluate $\alpha$
- Would be useful for the investigation of volcanic forcing and feedback in CMIP6 if
ensemble experiments had only historical aerosol forcing, to diagnose the climate
response. Further, with AGCMs with prescribed sea surface conditions, to diagnose the
radiative forcing.
- _Do other models also exhibit a cloud adjustment and a lower climate sensitivity for
volcanic forcing?_

### 2016 — Santer et al.: Volcanic effects on climate

> DOI: [10.1038/nclimate2859](https://doi.org/10.1038/nclimate2859)

- Uncertainties in $\Delta T_{(t)}^{\mathrm{Vol}}$ are larger than what was reported by
Johansson et al. (2015).
- El Niño in the 1980- and 90s masks cooling from El Chichón and Pinatubo and hamper
reliable estimation of the true cooling signal.
- Concerning Johansson et al. infer a posterior average estimate of $F^{\mathrm{Pn}}$
that is substantially smaller than that obtained from observations.

### 2016 — Lovejoy and Varotsos: Scaling regimes and linear/nonlinear responses of last millennium climate to volcanic and solar forcings

> DOI: [10.5194/esd-7-133-2016](https://doi.org/10.5194/esd-7-133-2016)

- One study suggested that volcanic forcing never equilibrates (too little time in
between eruptions, eruptions occur over all observed timescales)
- Volcanic forcings were seen to be strong at annual scales but decreasing ($H<0$) while
the solar forcing was small at annual scales and increasing ($H>0$)

### 2016 — Rypdal and Rypdal: Late Quaternary temperature variability described as abrupt transitions on a $1/f$ noise background

> DOI: [10.5194/esd-7-281-2016](https://doi.org/10.5194/esd-7-281-2016)

- The $1/f$ noise characterization of the temporal fluctuations in global mean surface
temperature is robust — accurate for the Holocene climate
- Processes that exhibit power-law structure functions and strictly concave scaling
functions can be characterized as multifractal intermittent
- For a monofractal (monoscaling) process, the scaling function is linear in
- The analysis gives no evidence of multifractal intermittency in the temperature
records
- Multifractal intermittency implies that amplitudes of random fluctuations are
clustered in time on all timescales (e.g., intermittent turbulence). This is not
observed here, most reasonably modelled as monofractals

### 2016 — Rypdal and Rypdal: Comment on “Scaling regimes and linear/nonlinear responses of last millennium climate to volcanic and solar forcings" by S. Lovejoy and C. Varotsos (2016)

> DOI: [10.5194/esd-7-597-2016](https://doi.org/10.5194/esd-7-597-2016)

- The question is not whether non-linearities are present in the Zebiak-Cane or GCM
models (it is), but whether these non-linearities are detectable in the global
temperature response
- No reason why responses should be more linear on short than on long timescales, in
particular not the response to burst-like volcanic forcing

### 2017 — Otto-Bliesner et al.: Climate variability and change since 850 C.E.: An ensemble approach with the community earth system model (CESM)

> DOI: [10.1175/BAMS-D-14-00233.1](https://doi.org/10.1175/BAMS-D-14-00233.1)

- Includes 1500 years of an ensemble of 5 with only volcanic forcing (850-2005)
- All other forcings are constant at 850 levels (the first simulation year)

### 2017 — Knutti et al.: Beyond equilibrium climate sensitivity

> DOI: [10.1038/ngeo3017](https://doi.org/10.1038/ngeo3017)

- “But even more pressing is the debates about fair contributions for each country in
reducing emissions, helping others to do so, and adapt, and the lack of willingness to
step up and lead the pack.”
- Discrepancy and lack of progress? Models favour ECS in the upper part of the “likely”
range.
- A big concern is that many climate models share the same limitations, the same
imperfect observations
- Clouds are the largest uncertainty feedback
- Easier to produce a model with good performance on mean climate and a climate
sensitivity above the IPCC range
- Uncertainties also in observations, making even multidecadal trends uncertain
- _Most pressing issue:_ Growing concern that a single constant climate feedback
parameter (λ) is unrealistic. Neglects differences in the temperature response to
forcing that are not captured by a forcing efficacy.
- Therefore, ECS also (including TCR) depends strongly on ocean heat uptake and
circulation response
- Forcings may not be additive, but depend on the type and magnitude of the forcing
- ECS estimates assuming a constant λ are probably underestimates

### 2018 — Theodorsen et al.: Universality of Poisson-driven plasma fluctuations in the Alcator C-Mod scrape-off layer

> DOI: [10.1063/1.5064744](https://doi.org/10.1063/1.5064744)

### 2018 — Sukhodolov et al.: Stratospheric aerosol evolution after Pinatubo simulated with a coupled size-resolved aerosol-chemistry-climate model, SOCOL-AERv1.0

> DOI: [10.5194/gmd-11-2633-2018](https://doi.org/10.5194/gmd-11-2633-2018)

- A good resource for what processes affect and are affected by volcanic eruptions
- An intercomparison revealed that modelled volcanic sulphate deposition varies
substantially in timing, spatial pattern, and magnitude between the models
- Still, no clear understanding of which model is closer to reality in describing the
stratospheric aerosol distribution
- Even with a fine aerosol size resolution, resulting sedimentation can be biased due to
the model’s numerical scheme
- There is rising interest among the climate community in global models with interactive
aerosol microphysics, partly because of the unclear role of major and smaller
volcanoes in the future climate (e.g., Bethke et al., 2017; Klobas et al., 2017)
- Initially, SAGE II data experience a saturation effect, and HIRS data is better to
use, but as the atmosphere becomes sufficiently transparent it is expected that SAGE
II measurements provide more accurate aerosol extinction
- Lower tropical stratospheric warming after major volcanic eruptions is one of the key
features of volcanic influence on climate
- Numerically diffusive methods must be avoided

### 2019 — Rugenstein et al.: LongRunMIP: Motivation and Design for a Large Collection of Millennial-Length AOGCM Simulations

> DOI: [10.1175/bams-d-19-0068.1](https://doi.org/10.1175%2Fbams-d-19-0068.1)

- Reference material

### 2020 — Ghil and Lucarini: The physics of climate variability and climate change

> DOI: [10.1103/RevModPhys.92.035002](https://doi.org/10.1103/RevModPhys.92.035002)

- Reference material

### 2020 — Danabasoglu et al.: The Community Earth System Model Version 2 (CESM2)

> DOI: [10.1029/2019MS001916](https://doi.org/10.1029/2019MS001916)

- Reference material

## To-Read

### 2016 — Otto-Bliesner et al.: Climate Variability and Change Since 850 CE: An Ensemble Approach with the Community Earth System Model

> DOI: [10.1175/BAMS-D-14-00233.1](http://dx.doi.org/10.1175/BAMS-D-14-00233.1)

### 2016 — Colose et al.: The influence of volcanic eruptions on the climate of tropical South America during the last millennium in an isotope-enabled general circulation model

> DOI: [10.5194/cp-12-961-2016](https://doi.org/10.5194/cp-12-961-2016) (Also see his
> [Google Scholar page](https://scholar.google.com/citations?hl=no&user=rx9dKowAAAAJ&view_op=list_works&sortby=pubdate))

### 2016 — Colose et al.: Hemispherically asymmetric volcanic forcing of tropical hydroclimate during the last millennium

> DOI: [10.5194/esd-7-681-2016](https://doi.org/10.5194/esd-7-681-2016)

### 2011 — Toohey et al.: The influence of eruption season on the global aerosol evolution and radiative impact of tropical volcanic eruptions

> DOI: [10.5194/acp-11-12351-2011](https://doi.org/10.5194/acp-11-12351-2011)

### 2014 — Toohey et al.: The impact of volcanic aerosol on the Northern Hemisphere stratospheric polar vortex: mechanisms and sensitivity to forcing structure

> DOI: [10.5194/acp-14-13063-2014](https://doi.org/10.5194/acp-14-13063-2014)

### 2019 — Toohey et al.: Disproportionately strong climate forcing from extratropical explosive volcanic eruptions

> DOI: [10.1038/s41561-018-0286-2](https://doi.org/10.1038/s41561-018-0286-2)

### Referenced Gregory et al. (2016)

Are any of these relevant?

- [Obata and Adachi (2019)](https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2018JG004696)
- [Marshall et al. (2020)](https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2020GL090241)
- [Goodwin and Cael (2021)](https://esd.copernicus.org/articles/12/709/2021/)
- [Marshall et al. (2021)](https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2020JD033578)
- [Marshall et al. (2022)](https://link.springer.com/article/10.1007/s00445-022-01559-3)
- [Gunther et al. (2022)](https://journals.ametsoc.org/view/journals/clim/35/24/JCLI-D-22-0306.1.xml)
- [Dogar et al. (2023)](https://link.springer.com/article/10.1007/s41748-022-00331-z)

## Motivation

- Comment in Nature:
[Huge volcanic eruptions: time to prepare](https://www.nature.com/articles/d41586-022-02177-x),
[DOI](https://doi.org/10.1038/d41586-022-02177-x)
- Mentioned on
[nrk](https://www.nrk.no/trondelag/eksperter-mener-verden-er-for-darlig-forberedt-pa-en-mulig-vulkankatastrofe-1.16084751)

[volc-cluster-ctrl]: https://view.es-doc.org/?renderMethod=name&project=cmip6&type=cim.2.designing.NumericalExperiment&client=esdoc&name=volc-cluster-ctrl
[volc-cluster-mill]: https://view.es-doc.org/?renderMethod=name&project=cmip6&type=cim.2.designing.NumericalExperiment&client=esdoc&name=volc-cluster-mill
[past1000-volc-cluster]: https://gmd.copernicus.org/articles/10/4005/2017/gmd-10-4005-2017.pdf