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A revision of the Earth’s energy balance framework
A. E. DesslerDept. of Atmospheric Sciences
Texas A&M University
T. Mauritsen and B. StevensMax Planck Institute for Meteorology
abrupt 4xCO2 GFDL-CM3
Year
∆R∆T
s
abrupt 4xCO2 GFDL-CM3
Year
∆R∆T
s
abrupt 4xCO2 GFDL-CM3
Year
∆R∆T
s
abrupt 4xCO2 GFDL-CM3
Year
∆F∆R∆T
s
abrupt 4xCO2 GFDL-CM3
∆Ts
∆R
Year
Year
abrupt 4xCO2 GFDL-CM3
∆R∆T
s
Year
abrupt 4xCO2 GFDL-CM3
∆R
∆R = ∆F + λ ∆Ts
∆Ts
∆R = ∆F + λ ∆Ts = 0
At equilibrium:
∆R = ∆F + λ ∆Ts
∆Ts = -∆F/λ
= 0
At equilibrium:
∆R = ∆F + λ ∆Ts
∆Ts = -∆F/λ
= 0
At equilibrium:
∆T2xCO2 = -∆F2xCO2/λ = ECS
∆R = ∆F + λ ∆Ts
∆Ts = -∆F/λ
= 0
At equilibrium:
∆T2xCO2 = -∆F2xCO2/λ = ECS
Q: is this the right way to describe our planet’s energy balance?
∆R = ∆F + λ ∆Ts
∆Ts = -∆F/λ
= 0
At equilibrium:
∆T2xCO2 = -∆F2xCO2/λ = ECS
Q: is this the right way to describe our planet’s energy balance?
Q: is the response of the TOA flux linear in global avg. surface
temperature?
6
satellite obs. record (2000-2016)
7
satellite obs. record (2000-2016)
∆R = ΔF + λ ΔTS
7
satellite obs. record (2000-2016)
∆R = ΔF + λ ΔTS CERES
7
satellite obs. record (2000-2016)
∆R = ΔF + λ ΔTS obs.CERES
7
satellite obs. record (2000-2016)
∆R = ΔF + λ ΔTS obs.CERES
small
∆R
∆Ts
∆R = ΔF + λ ΔTS
∆R
∆Ts
∆R = ΔF + λ ΔTS
∆R
∆Ts
Slope = λ (W/m2/K)
∆R = ΔF + λ ΔTS
CER
ES E
d. 4
, EBA
F
ERAi
Global, monthly avg., detrended, 3/2000-9/2016
CER
ES E
d. 4
, EBA
F
ERAi
Global, monthly avg., detrended, 3/2000-9/2016
CER
ES E
d. 4
, EBA
F
ERAi
Global, monthly avg., 3/2000-9/2016Lesson: λ∆T is not a very good parameterization for ∆R (for
interannual variability)
CER
ES E
d. 4
, EBA
F
ERAi
Global, monthly avg., 3/2000-9/2016Lesson: λ∆T is not a very good parameterization for ∆R (for
interannual variability)
Should not be surprising: 90% of TOA LW radiation emitted
by atmosphere, not surface
12
Derive ECS & λ from 20th century record
∆R = ΔF + λ ΔTS
12
Derive ECS & λ from 20th century record
∆R = ΔF + λ ΔTS obs.
12
Derive ECS & λ from 20th century record
∆R = ΔF + λ ΔTS climate model
obs.
12
Derive ECS & λ from 20th century record
∆R = ΔF + λ ΔTS climate model
obs.OHC
13
∆R = ΔF + λ ΔTS climate model
obs.
λ ≈ -2 W/m2/K ECS ≈ 1.5-2.0 K
OHC
Derive λ from 20th century record
13
∆R = ΔF + λ ΔTS climate model
obs.
λ ≈ -2 W/m2/K ECS ≈ 1.5-2.0 K
OHC
This anchors the low end of the IPCC's ECS range to 1.5 K
Derive λ from 20th century record
14
∆R = ΔF + λ ΔTS
ΔF obs.
ΔR ΔTS
modelssame same same
λ ≈ -2 W/m^2 λ ≈ -1.3ECS < 2 K ECS 2-4.5 K
14
∆R = ΔF + λ ΔTS
ΔF obs.
ΔR ΔTS
modelssame same same
λ ≈ -2 W/m^2 λ ≈ -1.3ECS < 2 K ECS 2-4.5 K
Perfect model experiment
• 100-member MPI-ESM1.1 ensemble – model producing output for CMIP6
• 1850-2005; identical historical forcing • only difference is the initial conditions
15
16
17
For each ensemble member …
∆R = ΔF + λ ΔT
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For each ensemble member …
∆R = ΔF + λ ΔT
solve for this
18
λ = ∆(R-F)/∆Ts W/m2/K
18
λ = ∆(R-F)/∆Ts W/m2/K
internal variability
19
λ = ∆(R-F)/∆Ts ECS = -∆F2xCO2/λ
19
λ = ∆(R-F)/∆Ts ECS = -∆F2xCO2/λ
19
λ = ∆(R-F)/∆Ts ECS = -∆F2xCO2/λ
We only have one realization of the 20th century, so there’s no guarantee that λ and ECS based on these
calculations are good estimates
20
revised framework
∆R = ΔF + Θ ΔTA
20
revised framework
∆R = ΔF + Θ ΔTA 500-hPa tropical
temperatures
20
revised framework
∆R = ΔF + Θ ΔTA 500-hPa tropical
temperatures
following Trenberth, Murphy, Spencer
20
revised framework
∆R = ΔF + Θ ΔTA 500-hPa tropical
temperaturesConverts change
in TA to flux; replaces λ
following Trenberth, Murphy, Spencer
CERES Ed. 4 TOA fluxes & ERA-interim temperatures monthly avg. detrended anomalies
Ts = global avg. surface temperature TA = tropical avg. 500-hPa temperature
22
λ = ∆(R-F)/∆TSΘ = ∆(R-F)/∆TA
22
λ = ∆(R-F)/∆TSΘ = ∆(R-F)/∆TA
confirmed in CMIP5 control runs
23
∆R = ΔF + Θ ΔTA
• Can we use our new framework to better predict ECS?
23
∆R = ΔF + Θ ΔTA
• Can we use our new framework to better predict ECS?
• Use measurement of Θcontrol from CERES to constrain ECS
23
∆R = ΔF + Θ ΔTA
• Can we use our new framework to better predict ECS?
• Use measurement of Θcontrol from CERES to constrain ECS
• In CMIP5 ensemble, Θcontrol ≈ Θabrupt4xCO2
25
∆R = ΔF + Θ ΔTA
3.45 K
3.45 K
13 of 15
3.45 K3 of 13
3.45 K
3.45 K
ECS < 3.5 K
• the conventional energy balance framework has problems — TOA flux is not strongly related to surface temperature
• creates problems inferring ECS from historical data
• new framework using atmospheric temperature: ECS < 3.5 K
31
Conclusions
backup slides
32
CERES ∆R at each latitude vs. ∆Ts at that same latitude detrended monthly avg. anomalies
global vs. tropical T500
35
20th century obs. record
∆R = ΔF + λ ΔT
35
20th century obs. record
∆R = ΔF + λ ΔT based on fixed SST runs
35
20th century obs. record
∆R = ΔF + λ ΔT based on fixed SST runs
ensemble
35
20th century obs. record
∆R = ΔF + λ ΔT based on fixed SST runs
ensembleensemble
∆T
∆R
CMIP5 control runs (NorESM1-M)
months
∆T
∆R
CMIP5 control runs (NorESM1-M)
months
∆T
∆R
CMIP5 control runs (NorESM1-M)
months
∆T
∆R
CMIP5 control runs (NorESM1-M)
months
∆T
∆R
CMIP5 control runs (NorESM1-M)
months
∆T
∆R
CMIP5 control runs (NorESM1-M)
months
37
38
CCSM4 CMIP5 control run
λ = ∆(R-F)/∆Ts
Θ = ∆(R-F)/∆T500t
39
CMIP5 control runs
5-95% percentile range
2.4 K
3.45 K
2.4 K
3.45 K
2.4 K
3.45 K
2.4 K
3.45 K 3 of 13 models
2.4 K
3.45 K
11 of 11 models