The New York Times just published a story about the natural gas leak in Porter Ranch, California. According to the Science Magazine article they reference in their report, 97,100 metric tons of methane were released into the atmosphere.

This sounds like a lot (and it is!), but relative to the rest of U.S. greenhouse gas emissions, it’s a drop in the bucket.

The chart below shows how the Porter Ranch leak compares. Each represents the equivalent of 2.4 million tons of carbon dioxide (abbreviated CO2e).

Porter Ranch Natural Gas Leak


Total U.S. Natural Gas Leakage


Methane Emissions from U.S. Cattle


Total U.S. Methane Emissions


U.S. Greenhouse Emissions from Consumer Vehicles


Total U.S. Greenhouse Emissions


Data Source

Each year, the EPA publishes a Greenhouse Gas Inventory Report, detailing greenhouse emissions in the United States. The most recent data is from 2014, so I used that as a comparison point.

Comparing Methane and CO2 Emissions

Methane has a much more potent greenhouse effect than CO2. However, methane lasts only about 10 years in the atmosphere, whereas CO2 lasts for centuries. To account for this, climate scientists use a value called global warming potential (GWP) to normalize the greenhouse impact of all gases to that of CO2.

GWP has an associated time scale, which is usually 100 years. The EPA uses a 100-year GWP value of 25 for methane. This means that over the course of 100 years, a ton of methane in the atmosphere will cause as much global warming as 25 tons of CO2.

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