California Air Resources Board

Short-lived climate pollutants (SLCP) are powerful climate forcers that have relatively short atmospheric lifetimes. These pollutants include the greenhouse gases methane and hydrofluorocarbons (HFC), and anthropogenic black carbon. Because SLCP impacts are especially strong over the short term, acting now to reduce their emissions can have an immediate beneficial impact on climate change and public health. Senate Bill (SB) 1383 (Lara, Chapter 395, Statutes of 2016) set limits for statewide reductions in SLCP emissions of 40 percent below 2013 levels by 2030 for methane and HFCs and 50 percent below 2013 levels by 2030 for anthropogenic black carbon.

This page contains data and documentation for the SLCP inventories and projections used in the SLCP Reduction Strategy (Strategy). The Strategy was developed pursuant to SB 605 (Lara, Chapter 523, Statutes of 2014) and SB 1383. The SLCP inventories and projections contain source-specific emission estimates for methane, HFCs, and black carbon for the years 2000, 2013, 2020, and 2030. Information on sulfuryl fluoride emissions developed at the same time are also provided. Emissions estimates provided below are based on data available in 2015 unless otherwise noted. For the Methane and Short-Lived Hydrofluorocarbon Inventories, the methods used to calculate 2000 and 2013 emissions are described in the Assembly Bill 32 Greenhouse Gas Emissions Inventory (AB 32 GHG Inventory) 2014 edition Comprehensive Method Report [pdf] and the 2015 edition Method Updates [pdf] document. The latest edition of the AB 32 GHG Inventory includes CARB's most recent emission estimates for methane and HFCs for the year 2000 onward. Recognizing how damaging SLCPs can be over the short-term, the SLCP inventories are provided using both 100-year global warming potentials (GWP) and 20-year GWPs.

Methane Inventory

Methane is produced through anaerobic (without oxygen) decomposition of waste in landfills, animal digestion, decomposition of animal wastes, production and distribution of natural gas and petroleum, coal production, and incomplete fossil fuel combustion. The Methane Inventory and Projection documents (below) rely on data from the 2015 edition of the AB 32 GHG Inventory.

Methane Inventory and Projection (100-yr AR4 GWP) [pdf]
Methane Inventory and Projection (20-yr AR4 GWP) [pdf]
Methodology for Projecting California's Methane Emissions [pdf]

Short-Lived Hydrofluorocarbon Inventory

HFCs constitute a class of fluorinated compounds with a wide range of lifetimes and global warming potentials (GWPs). Unlike many other GHGs, HFCs have no significant natural sources and are generated almost entirely from human-related activities. The Short-Lived HFC Inventory and Projection documents (below) include emissions estimates for the following HFCs: HFC-125, HFC-134a, HFC-143a, HFC-152a, HFC-227ea, HFC-245fa, HFC-32, HFC-365mfc, and HFC-43-10mee. These emission estimates rely on data from the 2015 edition AB 32 GHG Inventory.

Short-Lived HFC Inventory and Projection (100-yr AR4 GWP) [pdf]
Short-Lived HFC Inventory and Projection (20-yr AR4 GWP) [pdf]
Methodology for California's High GWP Gases Emissions Inventory [pdf]

Black Carbon Inventory

Ambient particulate matter (PM) consists of a complex mixture of chemical compounds. Black carbon is the carbonaceous fraction of PM that absorbs all wavelengths of visible solar radiation and contributes to atmospheric warming. The Black Carbon Inventory uses elemental carbon speciation profiles developed by CARB as a proxy for black carbon. Speciation profiles are applied to PM_2.5 mass emissions to estimate black carbon emissions. The emissions data below is provided in two categories: forestry and non-forestry. The forestry category includes non-agricultural prescribed burning and wildfire emissions while the non-forestry category includes off-road mobile, on-road diesel, residential wood combustion emissions, and other emissions sources. Emissions from the forestry category are not included in the black carbon reduction limit.

California's 2017 black carbon emissions were estimated to be approximately 8 MMTCO₂e in a preliminary estimate developed by CARB for the 2022 Scoping Plan Update.

Non-Forestry Black Carbon Inventory

Non-Forestry Black Carbon Inventory and Projection (100-yr AR5 GWP) [pdf]
Non-Forestry Black Carbon Inventory and Projection (20-yr AR5 GWP) [pdf]
2015 Black Carbon Inventory Technical Support Document [pdf]

Forestry Black Carbon Data

Black carbon emissions from forestry activities exhibit high year-to-year variability and large uncertainty in current and future emissions. To provide a more representative view of emissions without large year-to-year variability driven by natural forces, forestry emissions were calculated as a ten-year average.

Annualized California Forestry Black Carbon Emissions

Sulfuryl Fluoride Inventory

Sulfuryl fluoride (SO₂F₂) is a fluorinated gas with a lifetime of 36 years. It is used as a pesticide for building fumigation and post-harvest storage of commodities, but is not licensed for use in agricultural fields. Sulfuryl fluoride was believed to have a negligible GWP until 2009, when new research assigned it a 100-year GWP of 4,090 and a 20-year GWP of 6,840. Sulfuryl fluoride is not included in the AB 32 GHG Inventory because it was not identified as a high-GWP gas when AB 32 was enacted.

The Department of Pesticide Regulation (DPR) tracks usage of sulfuryl fluoride. A summary of 2013 emissions based on DPR data is shown below. Usage for other years can be obtained from DPR.

2013 California Sulfuryl Fluoride Emissions

* Totals may not add due to rounding

For Strategy drafts and additional SLCP-related sources, visit SLCP Resources. For further program information, visit the Short-Lived Climate Pollutants Program.