Observational Approaches for Climate Treaty Verification:

Atmospheric observations provide the only source of independent information through which treaty compliance can be directly measured.

• Our goal is to detect a change in emissions of 5% over 5 years.

Year-to-year fluctuations in both human and natural emissions make it difficult to interpret changes on shorter time scales in term of treaty goals

•In order to achieve this goal we must:• Distinguish natural and anthropogenic sources• Capture monthly averages to account for seasonal variations• Obtain covariate information to help distinguish natural and human contributions, which will also provide information on sectoral contributions

• Our strategy is cross-cutting in space and time in order to yield highly constrained estimates. •Space-based• Ground-based

Space-based: 3 tiers of Satellites

1.AIRS-like (~4 km, broad vertical weight)• Global coverage• Coarse spatial resolution• 1-day revisit time• Cannot see Surface

2.OCO-like (total column)• 1 or 2 satellites• 7-15% coverage each• ~2-week revisit time• ~1 km spatial resolution• ~1 ppm measurement precision• Sees to the Surface• Provides contextual information about high-emitting regions

3.Targeted (total column, regional focus)• Multiple satellites• Focus on specific locations of

interest (e.g. cities, power plants) for extended periods of time

• Covariates for Satellite Observations of CO2

• CO & NOx can help disaggregate CO2 by sources

• Cloud-clearing or detection in small gaps capability is essential

• Current technology permits Daytime measurements only

Ground-Based • Concepts

• Target both large, local sources, which contribute a significant portion of national emissions, and can be monitored directly, plus global scale background large "plumes" from continental areas.

•Requirements• Links to transport model to determine emissions from the observed concentrations• An a-priori emissions inventory (provides spatial/temporal information)

• Site logistics for urban measurements• Density: 1 site per city usually OK• Locations: In the center of the city, not too close to large sources• Sampling frequency: High-frequency

• Capabilities• 5% change detection• CO helps with source disaggregation