Download Solar Forcings of the Climate System π σ Does solar variability influence climate?

Solar Forcings of the Climate System
Does solar variability influence climate?
S o (1 − albedo)πRE2 = FIR 4π RE2
So
(1 − albedo) = FIR = σTe4
4
⎧ So
⎫
Te = ⎨ (1 − albedo)⎬
⎩ 4σ
⎭
1
4
by Peter Pilewskie, April 20, 2007
Earth, Venus, and Mars
Planet
S
(W m-2)
a
Te
(K)
Ts
(K)
Earth
Venus
Mars
1361
2600
600
0.3
0.77
0.17
255
230
216
288
753
216
Greenhouse Effect
• What is the Greenhouse Effect?
• First, what it is not:
–
–
–
–
A greenhouse effect.
The atmosphere does not trap heat, nor does it trap radiation.
The atmosphere does not “re-radiate” radiation that it has (not) trapped.
The atmosphere does not act like a blanket.
• The Greenhouse Effect: the Earth’s surface receives
radiation from two sources:
– Sun (60%)
– Atmosphere (40%)
Where Does the Atmosphere Get Its Energy?
Large-scale energy sources that act continuously or quasicontinuously in the
atmosphere and at its boundaries.
Heat Flux*
Heat Source
Solar Irradiance
Heat Flux from Earth's Interior
Radioactive Decay
Geothermal
Infrared Radiation from the Full Moon
Sun's Radiation Reflected from Moon
Energy Generated by Solar Tidal Forces in the Atmosphere
Combustion of Coal, Oil, and Gas in US (1965)
Energy Dissipated in Lightning Discharges
Dissipation of Magnetic Storm Energy
Radiation from Bright Aurora
Energy of Cosmic Radiation
Dissipation of Mechanical Energy of Micrometeorites
Total Radiation from Stars
Energy Generated by Lunar Tidal Forces in the Atmosphere
Radiation from Zodiacal Light
Total of All Non-Solar Energy Sources
* global average
Physical Climatology, W.D. Sellers, Univ. of Chicago Press, 1965
Table 2 on p. 12 is from unpublished notes from
H.H. Lettau, Dept. of Meteorology, Univ. of Wisconsin.
2
[W/m ]
340.25
0.0612
0.0480
0.0132
0.0102
0.0034
0.0034
0.0024
0.0002
6.8E-05
4.8E-05
3.1E-05
2.0E-05
1.4E-05
1.0E-05
3.4E-06
0.0810
Relative Input
1.000
1.8E-04
1.4E-04
3.9E-05
3.0E-05
1.0E-05
1.0E-05
7.0E-06
6.0E-07
2.0E-07
1.4E-07
9.0E-08
6.0E-08
4.0E-08
3.0E-08
1.0E-08
2.4E-04
Solar Forcing
The U.S. Climate Change Science Program (USCCP)
Vision for the Program and Highlights of the Scientific Strategic Plan, 2003
Key Gaps in the Science of Climate Change
The nature and causes of the natural
variability of climate and its interactions
with forced changes are uncertain:
•
•
Because of the large and still uncertain
level of natural variability inherent in the
climate record and the uncertainties in the
time histories of the various forcing agents
(and particularly aerosols), a causal
linkage between the buildup of
greenhouse gases in the atmosphere
and the observed climate changes
during the 20th century cannot be
unequivocally established.
The value of indirect effect of ozone
changes induced by solar ultraviolet
irradiance variations remains highly
uncertain.
Perturbation at TOA: FNETref – FNET+50%
Calculated using the on-line code at http://snowdog.larc.nasa.gov/cgi-bin/rose/flp0404/fup.cgi
SORCE Measures TSI and SSI
TIMED
SEE
Solar Radiation and Climate
Experiment (SORCE)
Instrument
λ Range (nm)
∆λ (nm)
TIM: Total Irradiance Monitor
TSI (all)
-
SIM: Spectral Irradiance Monitor
200-2700
1-30
SOLSTICE: Solar Stellar Irradiance
Comparison Experiment
115-320
0.1
XPS: XUV Photometer System
0.1-27, 121.6
7-10
SORCE spacecraft was
launched on 25 January
2003, and its mission is
through 2008.
http://lasp.colorado.edu/sorce/
27-Year TSI Data Record
Greg Kopp, SORCE Science Meeting, 20-22 Sept. 2006
Composite Relies on Continuity
Current climate record plan
relies on continuity and
mission overlap.
But why the offsets?
Greg Kopp, SORCE Science Meeting, 20-22 Sept. 2006
The SORCE/TIM and TSI Variations
• 2005 TSI Accuracy Workshop
indicated missing corrections to some
NIST
TSI instruments and possible causes
calculates
of instrument offsets
diffraction
should lower • NASA’s Glory program is creating the
TSI Radiometer Facility to compare
these reported
TSI instruments on an absolute scale
results.
• LASP will be taking a SORCE/TIM
ground instrument to NIST later this
year to perform power comparisons
– Other TSI instruments to follow
for NIST comparisons
• DeToma & White “Empirical Modeling
of TSI” Solar Physics paper:
– “The model for the TIM TSI time
series gives the best fit... TIM TSI
measurements are the most
Correction not yet applied by ACRIM or ERBE Teams
precise because of its new
instrumental design.”
Greg Kopp, SORCE Science Meeting, 20-22 Sept. 2006
340.25 W m-2
340.25
Energy budget within the atmosphere after Kiehl and Trenberth [1997]. The numbers give the globally and
annually averaged solar (left side of the figure) and longwave (right side) irradiances [W m-2].
Composites Rely on Continuity and Stability
Two primary TSI composites differ by 40 ppm/yr
caused by 2 years of marginal quality data – not
even a gap!
?
Greg Kopp, SORCE Science Meeting, 20-22 Sept. 2006
SSI Critical for Atmospheric and Climate Studies
Chemistry Climate Models Need SSI
GISS GCM [Rind et al., 2004; Shindell et al., 2006]
NCAR WACCM [Marsh et al., 2007]
HAMMONIA [Schmidt and Brasseur, 2006]
CMAM [Beagley et al., 1997]
•
•
Water (clouds) and aerosols dominate the
absorption and scattering in the visible and
near infrared
Atomic and molecular species dominate
absorption in the ultraviolet
[Figure from P. Pilewskie, Solar Physics, 2005]
A problem discovered at DOE ARM
Harrison et al., Geophys. Res. Lett. 26, pp. 1715-1718, 1999
SSI and Climate
Spectral Irradiance Contributions to Climate:
•
Mechanisms of climate response are highly wavelength dependent
– Direct surface heating for wavelengths > 300 nm
– UV absorption in the stratosphere and radiative and
dynamical coupling with the troposphere.
– Interaction with interact with internal modes of climate
variability (ENSO, NAO, and the QBO)
•
Greatest relative variability occurs in the ultraviolet; greatest
absolute variability occurs in mid visible (direct)
atmospheric extinction
irradiance at surface
300
•
•
Uncertainty in solar forcing must be reduced to separate natural from
anthropogenic radiative forcing.
TOA spectral distribution of solar radiation needed to interpret spectrally
dependent radiative processes in the atmosphere at the surface.
Short Time Scale Solar Variability
•
Solar time variability is a function of wavelength.
– TSI constrains the magnitude of the variability, but not its spectral
distribution.
– The Earth’s response to solar variability is wavelength dependent.
Jerry Harder, SORCE Science Meeting, 20-22 Sept. 2006
SIM Observed Solar Variability
Solar spectral variability produces variability in atmospheric heating
• Measured difference in spectral irradiance from “Quiet Sun” on 11 Feb. 2006 and two
active states:
- Plage dominated: 27 Oct. 2004
- Sunspot dominated: 15 Jan. 2005
• Instantaneous spectral heating rate calculated for the observed irradiance differences.
• Integrated heating differential over the visible and near-infrared spectrum is on the
order of 0.1 K day-1.
Pilewskie and Harder, SORCE Science Meeting, 20-22 Sept. 2006
Wavelength (µm)
TSIS Science Overview
Understanding Solar Forcing for Policy Decisions
Radiative Forcing of Climate Change: Expanding the Concept and
Addressing Uncertainties (2005), Committee on Radiative Forcing
Effects on Climate, THE NATIONAL ACADEMIES PRESS, 2005