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Achieving Climate Change Absolute Accuracy in Orbit



Bruce Wielicki, Joseph P. Rice


The Climate Absolute Radiance and Refractivity Observatory (CLARREO) mission will provide a metrology laboratory in orbit for the purpose of accurately measuring and attributing climate change. CLARREO measurements establish new climate change benchmarks with high absolute radiometric accuracy and high statistical confidence across a wide range of essential climate variables. CLARREO's inherently high absolute accuracy will be verified and traceable on-orbit to Systeme Internationale (SI) units. The benchmarks established by CLARREO will be critical for assessing changes in the Earth system and climate model predictive capabilities for decades into the future as society works to meet the challenge of optimizing strategies for mitigating and adapting to climate change. The CLARREO benchmarks are derived from measurements of the Earth's thermal infrared spectrum (5 m to 50 m), the spectrum of solar radiation reflected by the Earth and its atmosphere (320 nm to 2300 nm), and radio occultation from which accurate temperature profiles are derived. The mission has the ability to provide new spectral fingerprints of climate change, as well as to provide the first orbiting radiometer with accuracy sufficient to serve as the reference transfer standard for other space sensors, in essence serving as a "NIST in orbit". CLARREO will greatly improve the accuracy and relevance of a wide range of space-borne instruments for decadal climate change. Finally, CLARREO has developed new metrics and methods for determining the accuracy requirements of climate observations for a wide range of climate variables and uncertainty sources. These methods should be useful for improving our understanding of observing requirements for most climate change observations.
Bulletin of the American Meteorological Society


climate, satellite, remote sensing, spectrometer, radiometry, calibration


Wielicki, B. and Rice, J. (2013), Achieving Climate Change Absolute Accuracy in Orbit, Bulletin of the American Meteorological Society, [online],, (Accessed April 24, 2024)
Created October 27, 2013, Updated October 12, 2021