California Air Resources Board

Methane Overview

Methane is a potent greenhouse gas and the second largest contributor to human-caused climate change.  Methane currently is estimated to be responsible for about one quarter of anthropogenic global warming. Important considerations of methane: 

• Methane has a global warming potential that is 80 times higher than carbon dioxide over a 20-year timeframe, and 25 time higher over a 100-year period. 

• Methane concentrations in our atmosphere have doubled since pre-industrial times, with current global background levels around two parts per million. 

• Methane has a relatively short atmospheric lifetime of about 12 years, making it a “short-lived climate pollutant” (SLCP). 

• As a short-lived climate pollutant, mitigating methane emissions can have an immediate impact on reducing the effects of climate change.  

SOURCES OF METHANE IN CALIFORNIA 

According to the California Methane Inventory, the largest contributors to the State’s methane emissions are the agriculture, waste, and industrial sectors. In 2020, these three sectors were responsible for more than 90% of the State’s estimated methane budget. A breakdown of the major contributors to these sectors is provided below: 

STRATEGIES 

Under California’s short-lived climate pollutants bill (Senate Bill 1383), the State has adopted a goal to reduce emissions of methane 40% below 1990 levels by 2030. Numerous bills and programs address specific needs for achieving this goal. In 2015, Assembly Bill 1496 required the state to locate and monitor methane hotspots. Senate Bill 1371 required the California Public Utilities Commission to minimize natural gas leaks from transmission and distribution gas pipelines and facilities. California’s Landfill Methane Regulation required emissions monitoring at landfills and that 95% of the state deposits their waste in landfills that capture fugitive methane. CARB’s Oil and Gas Regulation sets emissions standards and best practices for applicable crude oil and natural gas facilities. California’ Dairy Digester Research & Development Program is managed by the California Department of Food and Agriculture with input from CARB.