Past and Future Climate Simulation Lecture 5 Geoengineering our Climate What is geoengineering? Focus on sunshade geoengineering Should we geoengineer.
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Past and Future Climate Past and Future Climate SimulationSimulation
Lecture 5Lecture 5
Geoengineering our Climate
What is geoengineering? Focus on sunshade geoengineering Should we geoengineer our climate?
So, what is geoengineering…..?
“The intentional large-scale manipulation of the environment, particularly manipulation that is intended to reduce undesired anthropogenic climate change’’
[Keith, Annu. Rev. Energy Environ., 2000]
[Keith, Annu. Rev. Energy Environ., 2000]
use less energy emit less CO2 change climate adapt
[based on Keith, Nature, 2001]
~100 papers to date….mostly ‘opinion’ pieces (cf. at least 50,000 on climate change!).
(1) Stratospheric sulphate aerosols
Pinatubo eruption, 1991
[Angel, PNAS, 2006]
“It seems feasible that it could be developed and deployed in 25 years at a cost of a few trillion dollars”[Angel, PNAS,
2006]
They would weigh a gram each. ~15 trillion within a 100,000- km-long cloud.
15 m
5 m
60 cm
(2) Solar “sunshade”
(3) Cloud seeding
(4) Crop albedo geoengineering
Ridgwell et al. 2009
(5) Iron fertilisation
SOIREE iron fertilisation experiment.
(6) Biochar
Royal Society Report on Geoengineering
Fully dynamic atmosphere, slab ocean: CCM3
3 experiments: pre-industrial, 2*CO2, geoengineered
CO2 radiation pertubation Solar radiation pertubation
ΔT due to CO2 doubling alone
ΔT due to CO2 doubling and reduction in solar constant – ‘geoengineered’
ΔT due to 4*CO2 alone
ΔT due to 4*CO2 and reduction in solar constant – ‘geoengineered’
Seaice, control
Seaice, geoengineered
Seaice, 4*CO2
GCM ocean, Energy balance atmosphere: UVic
2 experiments: A2 scenario, geoengineered
Plants use water more efficiently at high CO2 – less evapotranspiration
Failure of geoengineering
A2 geoengineered
3 simulations:
(1) Pre-industrial (PI)
(2) High CO2 (4* PI),
(3) High CO2 (4* PI), reduced solar constant
4*CO2
Pre-industrial
Geoengineered4.2% reduction in solar constant = 57 W/m2
Temperature anomaly, Geo - PreInd
Solar forcing, TOA
Solar forcing has strong meridional gradient. CO2 forcing balances in global mean but is more meridionally homogeneous
Annual mean surface temperature change Geoengineered - pre-industrial
Annual mean sea ice change Geoengineered - pre-industrial
Precipitation
Soil moisture Storm tracks (500mbar EKE)
ENSO
Control: σ=0.46
Geoengineered: σ=0.35
“Sunshade World” Temp
“CO2 World” Precip“Sunshade World” Precip
“CO2 World” Temp
Lunt et al, 2008
“Sunshade World” Temp
“CO2 World” Precip“Sunshade World” Precip
“CO2 World” Temp
What about Greenland??
The ice-sheet model
Ice-sheet model – GLIMMER. Based on Payne (1999).
Predicts evolution of ice-sheet geometry (extent, elevation).
Mass balance scheme (surface of ice-sheet)
Ice-sheet dynamics
Driven offline by temperature and precipitation from the GCM. Temperature downscaled using high-resolution orography and a constant lapse rate.
[Letreguilly et al, 1991] GLIMMER
[Stone et al, in prep]
control 4*CO2, Ridley et al, Journal of Climate, 2005
4*CO2
control 4*CO2 4*CO2, geoengineered
Irvine et al, 2009
4*CO2
4*CO2
4*CO2 with sunshade
SAT
Precip
Lunt et al. 2008
4*CO2 with sunshade
Anomaly compared to pre-industrial climate
Sunshade Geoengineering
Irvine et al, submitted to GRL.
Fractional Sunshade Geoengineering – regional issues
Irvine et al, 2010
Should we Geoengineer the Should we Geoengineer the climate?climate?
What are the climate changes? Can we What are the climate changes? Can we know them well enough?know them well enough?
Which scheme (or combination of schemes) Which scheme (or combination of schemes) minimizes minimizes damagedamage??
Who decides what Who decides what damagesdamages matter most? matter most? How to deal with the “winners” and How to deal with the “winners” and
“losers”?“losers”? ““Moral Hazard”Moral Hazard” Is it an ethical response to global warming?Is it an ethical response to global warming?
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