Modelling the climatic influence of Volcanoes

Paul Valdes, Peter Hopcroft, Jessy Kandlbauer

School of Geographical Sciences

University of Bristol

Structure of Talk

• Introduction: How do climate models

work?

– And how do we add volcanic forcing

• Case Studies:

– Warm winters

– Past climate response

– Super eruptions

– Biogeochemical responses

• Latest Results:

Climate Models

Starting point are the fundamental physics (e.g. Newton's Law,

Ideal Gas Equation etc.)

But many approximations required

Brief History of Climate

Models

Modelling Volcano-Climate

Interactions

• Stratospheric Aerosols

– Chemical Changes

• Modelling past changes

– Last Millennium

– Deglaciation

– Toba

– Super volcanoes

• Biogeochemical Perspectives

• Recent results for Tambora

Stratospheric Aerosol-

Climate Links

Mount Pinatubo

Winter (DJF) temperature response

following Mount Pinatubo

Robuck 2000

Lower Stratospheric Temperatures

Surface Air Temperature

Can Models reproduce

these features?

Kirchner et al 1999

Surface Air Temperature Lower Stratospheric Temperatures

Winter Warming

From Robuck 2000

Kirchner et al 1999

CMIP5 Model Results

Composite winter response for 9 largest eruptions since 1883

Driscoll et al 2012

Volcanic Indexes of Past

Eruptions

Robuck

2000

Last Millennium and

Volcanoes

Crowley 2000

How accurately do we know

past changes in climate?

Do tree rings underestimate rapid cooling following

volcanic eruptions?

Mann et al 2012

Blue curve

Tree ring data

Red curve

Model

simulations

But are the models

overestimating changes?

Tropical Marine Temperatures:

Black curve = observations

Other curves = CMIP5 model simulations

Vertical grey lines show the 1809 eruption

and Tambora

Northern Hemisphere Temperatures:

From Brohan et al, 2012

Observations based on instrumental data

Deglaciation:

Did volcanoes have a role?

Huybers and

Langmuir 2009

Super Eruptions (Toba)

DJF

JJA

Jones (GS) et al, 2005

Global Mean Surface Air

Temperature

Super Eruptions (Toba):

Did they impact on human evolution

Viable human

habitats before

Toba

Viable human

habitats after

Toba

From Jones SC 2012

Also see Petraglia et al 2012

Super volcanoes (Yellowstone)

Additional Effects of (Highly Reflective)

Ash Layer

Jones M et al 2007

Volcanoes and Climate

Biogeochemistry

Changes in CO2 following Mount Pinatubo

Black Line –

modelled

Dashed line –

Observations

Jones (C) and

Cox 1999

Summary (Part 1)

• The basic cooling impact of volcanic aerosols

probably well represented by climate models

– provided we know the forcing

• Past changes much more challenging to model

– We require better reconstructions of aerosol loads for

the past

• Biogeochemical responses of the Earth System

barely investigated.

• largest eruption in last 1000 years

• volume min 30-33 km3 DRE

• pyroclastic flows/ash fall caused over 11’000 deaths

• contaminated water and crop failure caused another

49’000 deaths

• 51 Mt of SO2 in the atmosphere in 24h

Indonesia

Java

Malaysia

Borneo Sulawesi

TAMBORA

1000 km

0.1 cm

1 cm

Tambora 1815

Tambora

Crowley et al 2008

Earth System Models

HadGAM2 HadGOM2

SEA ICE ATMOSPHERE-OCEAN

TRIFFID MOSES2

Collins et al 2011, GMD

Earth System Models UKCA

diat-HadOCC

TRIFFID MOSES2

HadGAM2 HadGOM2

SEA ICE ATMOSPHERE-OCEAN

Collins et al 2011, GMD

Model setup

•We use the pre-industrial coupled simulation of HadGEM2-ES (Jones et al 2011) •Tambora is imposed as a transient change in the stratospheric optical depth following Crowley et al 2008. •This is converted to a constant mmr above the tropopause • Aerosol scattering & absorption over the range 0.2-10μm • Assumed constant aerosol size distribution. •Ash deposition and other forcings are not included

Atmosphere: 1.875 x1.25 x38 levels Ocean: 1.0 x1.0 -0.33 x40 levels MOSES2-TRIFFID vegetation/land surface HadOCC – ocean carbon cycle UKCA – atmospheric chemistry

1 C global cooling

Response of the HadGAM2-ES Earth System Model

Surface air temperature ( C) Precipitation (mm/day)

1 C global cooling

Response of the HadGAM2-ES Earth System Model

Net Primary Productivity: Terrestrial Vegetation

C3 grasses C4 grasses

kgC/m2/yr NPP anomaly

Carbon reservoir changes

Soil Carbon

Veg Carbon

Soil respiration

NPP

Air-sea flux

Carbon fluxes

Carbon stores

c.f. 7-8 GtC cumulative uptake 4 years after Pinatubo (Jones & Cox, 2001)

Winter Warming?

1883-1991 average

Tambora

Ensemble mean

Stenchikov et al 2006

Ensemble members

Atlantic Meridional Overturning Circulation

Stenchikov et al 2009

latitude

Dep

th (

m)

1Sv =106 m3/s Control = 12Sv

Future work

• Winter warming – what causes this, and under which conditions? • What controls the AMOC under volcanic forcing? • What are the dominant controls on terrestrial and oceanic carbon cycle changes? • Can we test the influence of volcanic dust input on ocean productivity?