1. Accuracy Requirements for Climate Change
GSICS Meeting
William and Mary Universithy
Williamsburg, VA, March 4, 2013
Bruce Wielicki
NASA Langley Research Center
Hampton, Va

2. The Three Laws of Climate Change
Accuracy

3. The Three Laws of Climate Change
Accuracy, Accuracy

4. The Three Laws of Climate Change
Accuracy, Accuracy, Accuracy

5. Decadal Survey defines CLARREO
NOAA CLARREO
CERES (Clouds and Earth’s Radiative Energy System)
TSIS (Total Solar Irradiance Sensor)
NASA CLARREO
New accuracy for climate change
Solar reflected spectra: SI traceable relative uncertainty of 0.3% (k=2)
Infrared emitted spectra: SI traceable uncertainty of 0.1K (k=3)
Global Navigational Satellite System Radio Occultation: SI traceable uncertainty of 0.1K (k=3).
Three 90 degree orbits for diurnal cycle sampling
CLARREO is a Cornerstone of the Climate Observing System

6. Decadal Change Climate Science6

7. Examples of Key Climate Change Observations
Blue = CLARREO Solar Reflected Spectra Science
Red = CLARREO IR spectra & GNSS-RO Science
- Temperature
- Water Vapor
- Clouds
- Radiation
- Snow/Ice Cover
Earth's
Climate
Greenhouse Gases
Surface Albedo
Cloud Feedback
Water Vapor/Lapse Rate Feedback
Snow/Ice Albedo Feedback
Roe and Baker, 2007
50% of CLARREO Science Value is in Reflected Solar Spectra
50% of CLARREO Science Value is in Infrared Spectra & GNSS-RO
100% of CLARREO Science Value is in the Accuracy of the Data

8. Feedbacks Space/Time Sampling Requirements
Temperature Feedback
Water Vapor Feedback
Land and ocean zonal annual means required for temperature lapse rate and water vapor feedbacks, surface albedo feedbacks
1000 km regional scale required for cloud feedbacks
Seasonal cycle required for reflected solar: cloud feedback, snow/ice albedo feedback
Global Mean = -4.2 W/m2/K
Global Mean = 1.9 W/m2/K
Albedo Feedback
Cloud Feedback
Global Mean = 0.30 W/m2/K
Global Mean = 0.79 W/m2/K
Multi-model ensemble-mean maps of the temperature, water vapor, albedo, and cloud feedback, computed using climate response patterns from the IPCC AR4 models and the GFDL radiative kernels
Soden et al. 2008

9. Determining the Accuracy of Decadal Change Trends and Time to Detect Trends
A perfect climate observing system is limited in trend accuracy only by climate system natural variability (e.g. ENSO) (Leroy et al, 2008).
Degradation of accuracy of an actual climate observing system relative to a perfect one (fractional error Fa in accuracy) is given by: Fa = (1 + Σf 2i)1/2 - 1 , where f 2i = σ 2i τi / σ 2var τvar for linear trends where s is standard deviation, τ is autocorrelation time, σvar is natural variability, and σi is one of the CLARREO error sources.
Degradation of the time to detect climate trends relative to a perfect observing system (fractional error in detection time Ft) is similarly given by: Ft = (1 + Σf 2i)1/3 – 1
Degradation in time to detect trends is only ⅔ of degradation in accuracy.
Provides an integrated error budget across all decadal change error sources

10. Requirements focus on long term climate change
Decadal Change Trends
The absolute accuracy of climate change observations is required only at large time and space scales such as zonal annual, not at instantaneous field of view. Therefore all errors in climate change observation error budgets are determined over many 1000s of observations: never 1, or even a few.
Climate change requirements can be very different than a typical NASA Earth Science process mission interested in retrievals at instantaneous fields of view at high space/time resolution, where instrument noise issues may dominate instantaneous retrievals
So what accuracy relative to a perfect observing system is needed?
Requirements focus on long term climate change

11. Infrared Accuracy and Climate Trends
IPCC next few decades
temperature trends:
0.16C to 0.34C varying
with climate sensitivity
An uncertainty of half the
magnitude of the trend
is ~ 0.1C. Achieved
15 years earlier with
CLARREO accuracy.
Length of Observed Trend
High accuracy is critical to more rapid understanding of climate change

12. Accuracy and Climate Trends
Climate Sensitivity Uncertainty
is a factor of 3 (IPCC) which =
a factor of 9 uncertainty in climate
change economic impacts
Climate Sensitivity Uncertainty =
Cloud Feedback Uncertainty =
Low Cloud Feedback =
Changes in SW CRF/decade
(y-axis of figure)
Higher Accuracy Observations =
CLARREO reference intercal of
CERES = narrowed uncertainty
15 to 20 years earlier
High accuracy is critical to more rapid understanding of climate change

13. Decadal Change Reference Intercalibration Benchmarks: Tracing Mission Requirements

14. Science Instruments Infrared (IR) Instrument
Reflected Solar (RS) Instrument
Two Grating Spectrometers
Gimbal-mounted (2-axis)
Systematic error less than 0.3% (k=2) of earth mean reflectance
320 – 2300 nm contiguous spectral coverage
4 nm sampling, 8 nm res
0.5 km nadir FOV, ~ 100 km swath
Total Mass: 53.2 Kg
Total Power: 96 W
Fourier Transform Spectrometer
Systematic error less than 0.1K (k=3)
200 – 2000 cm-1 contiguous spectral coverage
0.5 cm-1 unapodized spectral resolution
17 km nadir FOV
Mass: 74.8 Kg
Power: 124 W
Small Instruments, Higher Accuracy, On-board Calibration Traceability
CLARREO ISS Mission Concept

15. Calibration Reference Spectrometers (IR/RS) for Global Climate, Weather, Land, Ocean satellite instruments
Provide spectral, angle,
space, and time matched orbit crossing
observations for all leo
and geo orbits critical
to support reference intercalibration
Endorsed by WMO &
GSICS (letter to Freilich)
Calibrate Leo and Geo
instruments: e.g.
- JPSS: VIIRS, CrIS, CERES
- METOP: IASI, AVHRR
- Landsat, etc land imagers
- Ocean color sensors
- GOES imagers/sounders
CLARREO Provides "NIST in Orbit": Transfer Spectrometers to SI Standards

16. The Three Laws of Climate Change: Accuracy, Accuracy, Accuracy
Summary
A perfect climate observing system is limited in trend accuracy only by climate system natural variability: actual observations further degrade climate model tests and observations of anthropogenic climate change.
Absolute SI traceable accuracy on orbit is critical to move beyond stability assumptions and to eliminate the large effect of data gaps
0.3% (k=2) requirement for the solar spectrum
0.07K (k=2) requirement for the infrared spectrum
These achieve climate change accuracy within 20% of perfect observations
These achieve climate change detection within 14% of perfect observations
GSICS plus CLARREO can achieve these levels of accuracy for the complete range of reflected solar and infrared earth observations from LEO & GEO
For further details, see the CLARREO overview paper accepted for publication in BAMS: Wielicki et al., 2013, and included references.
The Three Laws of Climate Change: Accuracy, Accuracy, Accuracy

17. CLARREO Presentations
Reflected Solar (RS) Spectrometer Accuracy Thome et al.
CLARREO Reference RS Intercal: Polarization Lukashin/Sun
CLARREO Reference RS Intercal: Sampling Lukashin et al.
CLARREO Infrared (IR) Spectrometer Accuracy Mlynczak et al.
CLARREO Reference IR Intercalibation Tobin et al.

18. Backup Slides

19. Economic Value of Climate Science

20. Accuracy and Climate Trends
Climate Sensitivity Uncertainty
is a factor of 3 (IPCC) which =
a factor of 9 uncertainty in climate
change economic impacts
Climate Sensitivity Uncertainty =
Cloud Feedback Uncertainty =
Low Cloud Feedback =
Changes in SW CRF/decade
(y-axis of figure)
Higher Accuracy Observations =
CLARREO reference intercal of
CERES = narrowed uncertainty
15 to 20 years earlier
High accuracy is critical to more rapid understanding of climate change

21. Value of Information (VOI) Calculation
Worked with Roger Cooke, RFF
IPCC lead author, chapter on economic impacts
Global Value of Improved Climate Information
CLARREO Climate Accuracy Framework
Social Cost of Carbon (IMSSC)
Integrated Climate /Economic Model
Current IPCC factor of 3 uncertainty in climate sensitivity = factor of 32 = factor of 9 uncertainty in economic impacts

22. VOI Calculation Baseline Assumptions 2205 2015 BAU emissions
Discount rate = 3%
Climate Sensitivity = IPCC (2007) uncertainty distribution
2205
SCC = $209 T
Baseline

23. Switch to Reduced Emissions
VOI Calculation
2015
BAU emissions
Assumptions
Discount rate = 3%
Climate Sensitivity = IPCC (2007) uncertainty distribution
Decision Trigger in 2055
2205
SCC = $209 T
2055
Switch to Reduced Emissions
2205
SCC = $65 T
Current Observing System

24. Improved accuracy yields savings of $11.7 T in net present value
VOI Calculation
2015
BAU emissions
Assumptions
Discount rate = 3%
Climate Sensitivity = IPCC (2007) uncertainty distribution
Decision Trigger in 2035
2205
SCC = $209 T
2035
Switch to Reduced Emissions
2205
SCC = $53 T
Improved Accuracy Observing System (2020 launch)
Improved accuracy yields savings of $11.7 T in net present value

25. Value of Information Parameters
Decision Context
Trigger Variable
∆T/decade
∆CRF/decade
Trigger Value
0.2C or 0.3C/decade
3C for 2X CO2
Confidence Level
80%, 95%
Launch Date
2020, 2025, 2030
Trigger Policy Change
DICE Optimal, Aggressive
Discount Rate
2.5%, 3%, 5%
Aerosol Forcing Obs
Start Date = CLARREO
Run 1000s of Monte Carlo cases with:
- Full pdf of climate sensitivity uncertainty in IPCC fit to Roe and Baker (2007)
- Gaussian climate natural variability as specified in the CLARREO BAMS article
for global mean temperature and SW cloud radiative forcing.
Results are the ensemble mean of the 1000s of Monte Carlo Simulations

26. How Sensitive are Results to Assumptions?
Parameter Change
CLARREO/Improved Climate Observations
VOI (Trillion US 2015 dollars, NPV)
3% discount rate
Baseline (blue values)
$11.7 T
BAU => AER
$9.8 T
0.3C/decade trigger
$14.4 T
2030 launch
$9.1 T
Delaying launch by 10 years reduces benefit by $2.6 T
Each year of delay we lose $260B of benefits

27. Value of Information Summary
Discount Rate
VOI for CLARREO/Improved Climate Observations
Cost of 30 yrs of improved
full climate observing system (4X current effort)
Payback Ratio
VOI / Obs Improvement Cost
2.5%
$17.6 T
$260B 65 3%
$11.7 T
$245B 45 5%
$3.1 T
$200B 15
All economic values in Net Present Value (NPV) in 2015 U.S. dollars
Even with the most pessimistic discount rate, the return on investment is large: factors of 15 to 65.

28. Science Value Matrix Concept

29. Why a Science Value Matrix?
Science is a cost/value proposition with uncertainty in both costs and value
Cost can be determined with ~ 30% uncertainty and is always addressed
Science value or priority for mission elements of design are rarely addressed, but could be and often should be
CLARREO has developed a new science value matrix concept to assist in:
Understanding cost/value
Understanding robustness of mission options
Understanding how one aspect of the mission (e.g. instrument accuracy) relates to others (science goals, climate record length, orbit sampling, instrument noise)
Understanding the impact of baseline vs threshold mission
Optimizing the mission design for cost/schedule/risk
Eliminating mission requirements "creep"
Communicating the mission design trades to NASA HQ
Moving the CLARREO science team discussions from "I feel" or "I think" or "I'm sure" to more quantitative basis on mission requirements
Improving and quantifying communication between scientists and engineers
A Science Value Matrix is a valuable tool to optimize mission design

30. Science Value Metrics
Science Value of a Science Objective = Science Impact * Trend Accuracy * (Record Length)0.5 * Verification * Risk
Science Impact
Uniqueness of CLARREO contribution
Importance of science objective to reducing climate change uncertainties
Accuracy
Accuracy in decadal change trends for a given record length
Climate Record Length
Sqrt(record length) reduction in noise from natural variability
Verification
SI traceable calibration verification
Independent instruments, analysis, observations (CCSP chapter 12, metrology)
Risk
Technological, budget, schedule, flexibility of mission options
Instrument Absolute Accuracy set for < 20% Trend Accuracy Degradation

31. Original Decadal Survey Mission: IR/IR/RO, IR/IR/RO, 2 year gap, IR/IR/RS/RS/RO
Original Decadal Survey Mission defined as 100% science value

32. CLARREO Mission Options
% of CLARREO
MCR Baseline Mission Science
Mission Cost
Estimate
($RYM)
Decadal Survey Concept (2007)
(11 instruments, 4 spacecraft, 4 launches)
112%
~ $1.6B
Launches 2017, 2019
MCR Baseline Mission Concept
(6 instruments, 4 smaller spacecraft or 2 larger)
100%
$800 - $1000
+ Launch Vehicle(s)
Launches 2018, 2020
MCR Minimum Mission Concept
(3 instruments, 1 spacecraft,
e.g. DAC-4 free flyer)
62%
$675 - $750
+ Launch Vehicle
Launch 2021
ISS Mission Concept
(2 instruments on ISS, RO is obtained from COSMIC-2)
73%
$340 - $390
cost includes launch
EV-2 ISS full cost guidelines
Cost estimates are full mission cost in real year dollars.
For MCR baseline and minimum mission, launch vehicle not included
ISS is highest science value/cost