A Short Paleo Thing, then Climate
Sensitivity
• Part 1: Going back to Maunder Minimum
– Two 11yr cycle reconstructions going back
• Part 2: Climate Sensitivity
– My scheduled talk
Plausibility of seeing the 11y cycle in surface temperature data
Estimated Response to 10 Cycle 0.1% TSI Forcing
based on a simple energy balance climate model with a
slab (mixed layer) ocean (North, Stevens, Wu, 2004)
Lag is long over ocean, short over land. Characteristic relaxation time over ocean
is a few years, over land it is about a month.
36 global sites
20 tropical sites
Simultaneous detection of solar cycle, volcanic, aerosol, greenhouse gases
90% confidence intervals
Noise-forced
North, G. R. and Q. Wu, 2001: Detecting climate signals using space-time EOFs. J. Climate, 14, 1839-1862.
Taylor Dome Data personally communicated by Petr Chylek
Taylor Dome: 600 yr Record
http://nsidc.org/data/docs/agdc/nsidc0108_wahlen/index.html
11yr cycle
22yr?
2
Smoothed in 5 Line bins
Refer to Miyahara here
11yr cycle
2
Smoothed in 5 Line bins
Why the AR1 background?
“weather’’
This leads to the AR1 spectrum
Klaus Hasselmann, 1976
We use a Gaussian Filter
for the bandpass ( =6lines)
Now apply the bandpass to the
Fourier Transform of the
temporal data and invert to get
the filtered time series.
11yr Band-Passed Time Series
14C
Delaygue&Bard, 2011
10Be
Band-Passed Taylor Dome
Time Series
Sunspots From
Foukal‟s book,
attributed to
Eddy
14C
10Be
Dye3 Core Results
Comments: The North Atlantic
is very noisy compared to the
interior of Antarctica. There is a
strong Red Noise (decadal to
Centennial) background in the
spectra.
Dye 3 Spectrum (3600y)
18y
11y ENSO/NAO-like Stuff (6-2y)
Dye 3 Band Pass Case
Bard, 2011
Dye3 ends
In 1871
Bard, 2011
Taylor
Dome
Dye3
Summary of Ice Core Findings
1. There are significant peaks at both Tidal and Sunspot
Frequencies.
2. After appropriate band-pass filtering, it appears possible to
reconstruct the temporal behavior of the envelope of
sunspot signal back to the Maunder Minimum. Match to
10Be & 14C deteriorates as we go back in time.
3. This seems to be a good consistency check of various
proxy methods of detecting solar activity.
4. Maybe we can learn about TSI during quiet SS periods.
5. This work suggests that there was no 11y cycle on Planet
Earth during Maunder Minimum.
6. A work in progress.
Climate Sensitivity
Gerald R. North
Department of Atmospheric
Sciences
Texas A&M University
SORCE Mtg, Sedona, AZ, 2011
Early Estimates of Sensitivity
Rate of IR flux out = Rate of Solar absorbed
M. I. Budyko
(Tellus,1969)
(Includes feedbacks)
The Charney Report (1979)
The Charney Report (1979)
The Charney Report (1979)
The Charney Report (1979)
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The Charney Report (1979)
Classics!
Famous guys horsing around in Tashkent:
Gates, Smag son, Reck, Smagorinski,
Saltzmann, Kim, Mintz, Stone, Manabe (1976)
The time on the clock indicates the time of an earthquake in Tashkent years before
24
25
Ruth Reck & Mikhail Budyko; to the left is Smagorinski, to the right is Yale Mintz;
taken near Abramov Glacier. (9/1976; photo by G. R. North)
26
GRN, Probably in Samarkand, 1976
The feedbacks will be covered by the
next two speakers, so let‟s go back to
the assertion that a doubling of CO2
leads to a reduction of 4W/m2 in the
outgoing radiation.
Exactly how does that work?
Consider the spectrum of the outgoing radiation.
First, take the Earth to be a black body radiator.
Temperature Profile in the Tropics
Radiative Transfer in an absorbing &
emitting atmosphere
emitted
Radiation
absorbed
Radiation
tiny volume
element
the atmospheric column
Flux to space
After summing over all
angles, we can get the
net fluxes up and down
from each slab.
This all has to be done
for each wavelength
(band).
Luckily this has been
going on for about 75
years and programs are
available.
km
CO2
Spectrum of outgoing radiation in the Clear Sky Tropics at near present time
Let‟s do CO2 alone (no other GHGs)
Doubling CO2
Thanks to the MODTRAN website, David Archer
The integral over the difference is 4.4Wm-2
Starting at 40ppm CO2 and doubling twice
Is it just a model? Can we believe this stuff?
CO2
O3
Published
1972
Ozone was
omitted in the
calculations
H2O
Myhre et al.
Line-by-Line Radiative Transfer Calculations
4.0Wm-2
IPCC: AR4
Some AOGCM Climate Equilibrium Sensitivities
(including Feedbacks)
Mean =3.21K
StDev=0.706K
Transient Sensitivity:
IPCC: AR4
“the global annual mean surface air temperature change (with
respect to a „control‟ run) averaged over a 20-year period
centered at the time of CO2 doubling in a 1% yr–1 compound
CO2 increase scenario.”
Mean=1.79K
StDev=0.38K
Important Note on Transient Response and Reversibility
The ocean can be apportioned into layers, heat is communicated to them from
the top. The deepest parts are also the most massive and therefore the most
sluggish to respond thermally (centuries). The upper layers respond rapidly (few
years).
This means that if we proceed to warm the planet for say half a century, then
decide to level the forcing, we will cool the planet some, but the lower sluggish
layers will take many decades to restore equilibrium.
Journal of Climate
I. M. Held, et al.
2010
The global mean surface air temperature in CM2.1 simulations with historical forcing
(black), with A1B forcing, stabilized in 2100 and extended for 200 additional years with
fixed forcing agents (blue), and four experiments in which the forcing agents are
returned to their 1860 values instantaneously in years 2000, 2100, 2200, and 2300 (red).
An estimate of the recalcitrant component of the response (thick black line) obtained by
averaging over years 10–30 after the switch-off.
The Charney Report (1979)
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