Climate Science and Policy

Blue carbon ecosystems (BCEs) are coastal vegetated habitats with a natural capacity to sequester and store vast amounts of carbon over long timescales. Given rising greenhouse gas concentrations and the subsequent increase in global efforts to reduce and offset emissions, BCEs are increasingly promoted as nature-based climate solutions. Their relevance to climate policy as a tool for climate change mitigation has garnered increasing attention, but heavily depends on ecosystem-specific evidence for carbon storage, sequestration permanence, monitoring feasibility, and governance compatibility. BCEs are also highly valued for providing many ecosystem services, biodiversity, and coastal resilience benefits. This study evaluates two prominent Norwegian BCEs: seagrass (Zostera marina) and macroalgal systems, primarily kelp forests and rockweed beds, as candidates for blue carbon policy and broader marine nature-based solutions. The analysis combines site-to-national carbon and ecosystem-service databases for seagrass and macroalgae, uncertainty analysis, spatial co-location screening from interactive mapping, and policy evaluation. Seagrass occupies a comparatively small national area (modeled extent ≈ 90 km²) but is directly compatible with sediment-based blue carbon accounting. Its sediment carbon density varies strongly among regions — low in the Barents Sea, much higher in Oslofjord and Skagerrak — reflecting the influence of differing environmental controls such as sediment dry bulk density, hydrodynamic exposure, and water column depth. Macroalgae dominate Norway's vegetated coastal area (kelp ≈ 7,417 km², rockweed ≈ 3,090 km²) and hold far larger estimated biomass-carbon pools and annual production fluxes; however, their carbon is living biomass, so any long-term climate benefit depends on export, deposition, and burial outside the production habitat, creating significant attribution and permanence uncertainties for carbon accounting. These differences imply different policy pathways. Norwegian seagrass is conceptually compatible with the Intergovernmental Panel of Climate Change (IPCC) Wetlands Supplement and could progress toward lower-tier inventory treatment as mapping, disturbance, and burial-rate data improve; its strongest near-term policy argument is the avoided degradation of existing sediment carbon. Macroalgae are better treated as an emerging blue carbon frontier and as high-priority biodiversity, fisheries, and coastal-resilience assets, entering policy through nature-based adaptation and co-benefits frameworks while export-driven accounting methods mature. The most defensible near-term pathway is therefore differentiated by habitat type: seagrass can begin IPCC Tier 1 accounting while developing capacity toward Tier 2 and Tier 3 readiness, whereas macroalgae should first be embedded into biodiversity and co-benefits frameworks while macroalgal carbon-fate research advances. Both ecosystems should be protected, monitored, and included into Nationally Determined Contributions immediately, with the differentiated pathway also phased so that each ecosystem is integrated further into formal carbon accounting and blue carbon governance as the underlying science matures.

Corporations operating in California are now required to publicly disclose their exposure to physical climate hazards under Senate Bill 261 (SB 261), yet these disclosures remain structurally disconnected from local and state adaptation planning processes. This study provides the first systematic empirical comparison of SB 261 corporate climate risk disclosures and California's public sea level rise adaptation planning ecosystem, examining the extent to which private and public actors assess comparable risks, operate at compatible spatial and temporal scales, and produce information that is decision-relevant for adaptation implementation. The research proceeds in two phases. Phase One analyzes 146 SB 261 disclosures alongside 20 public adaptation planning documents across six California coastal jurisdictions, with a comparative assessment of the risk assessment frameworks, tools, and methodologies used by each sector. Phase Two conducts semi-structured interviews with six corporate sustainability professionals and nine public adaptation planners to validate Phase One findings and surface the institutional conditions that would enable cross-sector collaboration. Findings reveal consistent and consequential mismatches between the two systems: corporate disclosures operate at portfolio scale with limited spatial resolution, short planning horizons, and no reference to public hazard tools, while public planners work at parcel level with standardized projections extending to 2100 and no awareness of what corporations in their jurisdictions have disclosed. Materiality divergence is the most fundamental gap, most corporations with mobile portfolios do not rate sea level rise as material, while every public planner treats it as central to their work. Despite these structural gaps, both sectors express conditional interest in collaboration, and specific institutional conditions, including mission alignment and fixed coastal asset exposure. Port-level regulatory authority and regionally embedded multi-jurisdictional agencies point toward viable entry points. The study concludes with five policy recommendations spanning data bridging, temporal alignment, cross-sector risk mapping, a coastal resilience credit framework, and a cross-sector industry network through which corporate disclosures can be made decision-relevant for local adaptation implementation.

Extreme heat is the leading cause of climate related mortality in the United States with marked socio-economic inequities. Yet, the vast majority of the scientific literature focuses on outdoor heat while people spend a considerable amount of time indoors. This study quantified the indoor-outdoor temperature differential (ΔT, defined as indoor minus outdoor temperature in °C) across 21 San Diego County census tracts using co-located PurpleAir sensors during the May-October 2023 warm season and examined its relationship with sociodemographic vulnerability, heat mitigation factors and sensor placement equity. Indoor temperatures exceeded outdoor temperatures in 90% of measured tracts, with a mean ΔT of +4.07 °C. On days meeting the San Diego County heat emergency threshold of 33.94 °C, the mean indoor-outdoor temperature difference decreased to +1.08 °C. Analysis of indoor temperature and sociodemographic variables found that no variable significantly predicted indoor temperature. However, outdoor temperature was significantly associated with poverty, renter-occupancy, non-white residents, indicating that heat disparities are reflective of geographic sorting into hotter inland areas. Green Space coverage using EVI data was strongly negatively correlated with cumulative environmental burden. Over 94.2% of San Diego County census tracts lacked an indoor sensor. Sensor placement was highly concentrated in coastal, higher income and lower burdened census tracts. These findings indicate the need for policy change, such as residential indoor temperature maximum standards, expanded indoor sensor coverage in high-burden communities, green space investment and air conditioning affordability programs.