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 AerosolClimate Links
Mount Pinatubo
Lower Stratospheric Temperatures
Surface Air Temperature
Winter (DJF) temperature response
following Mount Pinatubo
Robuck 2000
Can Models reproduce
these features?
Surface Air Temperature
Kirchner et al 1999
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?
Blue curve
Tree ring data
Red curve
Model
simulations
Mann et al 2012
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)
Global Mean Surface Air
Temperature
DJF
JJA
Jones (GS) et al, 2005
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.
Tambora 1815
•
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
Tambora
Malaysia
Borneo
0.1 cm
Sulawesi
Indonesia
Java
1 cm
TAMBORA
1000 km
Crowley et al 2008
Earth System Models
TRIFFID
MOSES2
ATMOSPHEREOCEAN
HadGAM2
SEA ICE
HadGOM2
Collins et al 2011, GMD
Earth System Models
UKCA
TRIFFID
MOSES2
diat-HadOCC
ATMOSPHEREOCEAN
HadGAM2
SEA ICE
HadGOM2
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
Response of the HadGAM2-ES Earth System Model
1 C global
cooling
Response of the HadGAM2-ES Earth System Model
1 C global
cooling
Surface air temperature ( C)
Precipitation (mm/day)
Net Primary Productivity: Terrestrial Vegetation
NPP anomaly
C3 grasses
kgC/m2/yr
C4 grasses
Carbon reservoir changes
Carbon fluxes
NPP
Air-sea flux
Soil respiration
Carbon stores
Soil Carbon
c.f. 7-8 GtC cumulative uptake 4
years after Pinatubo (Jones & Cox,
2001)
Veg Carbon
Winter Warming?
Ensemble mean
Tambora
Ensemble
members
Stenchikov et al
2006
1883-1991
average
Atlantic Meridional Overturning Circulation
Control = 12Sv
Depth (m)
1Sv =106 m3/s
latitude
Stenchikov et al 2009
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?