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

The Three Laws of Climate Change Accuracy

The Three Laws of Climate Change Accuracy, Accuracy

The Three Laws of Climate Change Accuracy, Accuracy, Accuracy

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

Decadal Change Climate Science 6

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

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

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

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

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

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

Decadal Change Reference Intercalibration Benchmarks: Tracing Mission Requirements

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

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

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

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.

Backup Slides

Economic Value of Climate Science

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

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

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

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

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

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

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

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.

Science Value Matrix Concept

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

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

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

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