Phase 2 (April 2026 – April 2027).

SMART-CH4 Phase 2 formally started on 9 April 2026 (T0) and runs for 12 months. Its kick-off meeting was held on 4 July 2026 — see News. Phase 2 attacks the two bottlenecks Phase 1 identified: point-source detections that cannot yet be added up into regional budgets, and a systematic stratospheric bias that distorts the emissions global models infer at the surface. See the Phase 1 results that motivated it, and the Phase 1 summary.

WP1 — Merging emission quantification scales, from local to regional (Lead: CEA-LSCE)

Point-source imagers deliver instantaneous plume rates by the thousand; area-scale mappers deliver time-averaged fluxes on a grid. No rigorous method exists to use both in one inversion. Phase 2 builds one.

WP1.1

Aggregation of fine-scale datasets and regional analytics
Lead: IUP-UB; with GHGSat, SRON, SPASCIA, Carbon Mapper

A uniform European hotspot database from EMIT, EnMAP, PRISMA, GHGSat, Tanager-1 and TROPOMI, with detection statistics and an assessment of reported uncertainties. GHGSat contributes a European Methane Emissions Intelligence Report synthesising observations since 2020.

WP1.2

Towards integrated multi-scale inversions
Lead: CEA

A full Bayesian framework in the Community Inversion Framework, jointly estimating individually detected sources and a sub-threshold residual population, linked by probability-of-detection functions. With Harvard, GHGSat and Carbon Mapper; leveraging work at SRON.

WP1.3

Prospective study of future constellations
Lead: CEA

OSSEs over Europe quantifying how much future high-resolution constellations would actually reduce uncertainty in national and sub-national budgets.

WP2 — Assessing and mitigating stratospheric biases in global inversions (Lead: VUA)

See the finding that created this WP: eleven global inversions checked against AirCore balloon profiles systematically overestimate stratospheric methane.

WP2.1

AirCore campaigns
Lead: LMD, with FMI

New profiles across tropical, mid and high latitudes, coordinated with MicroCarb validation at Aire-sur-l'Adour.

WP2.2

Assessment and mitigation
Lead: VUA

Five experiments separating transport, chemistry and observation error, including nudging the stratosphere to an ACE-FTS climatology corrected with AirCore, and a regional configuration (CHIMERE troposphere below 300 hPa, CAMS stratosphere above).

WP4/5/6 — Coordination, promotion, management (Lead: CEA)

Scientific coordination and partnerships, promotion, and project management. Coordination with IM4CA, MEDUSA and the EC-ESA ESSI cluster runs throughout.

Open challenges Phase 2 exists to address.

Straight from the Final Review. Honest, useful, and it is the rationale for Phase 2:

TIR spectroscopy needs further investment — especially toward isotopes and IASI-NG.
Hotspot quantification remains uncertain and sparse; cross-validation of methods and controlled release experiments are needed.
Integration across scales — turning point-source detections into regional budgets — is unsolved.
Regional inversions remain too sensitive to the choice of retrieval product and to resolution.
Global inversions are critically sensitive to bias, especially stratospheric bias in vertical and horizontal advection.