California Air Resources Board

What is Global Warming Potential?

Global Warming Potential, or GWP, is a measure of how destructive a climate pollutant is. Refrigerants today are often thousands of times more polluting than carbon dioxide (CO₂). The GWP of a gas refers to the total contribution to global warming resulting from the emission of one unit of that gas relative to one unit of the reference gas, CO₂, which is assigned a value of 1. GWPs can also be used to define the impact greenhouse gases will have on global warming over different time periods or time horizons. These are usually 20 years, 100 years, and 500 years. A time horizon of 100 years is used by regulators (e.g., the California Air Resources Board). CARB maintains a list of GWPs for some common refrigerants. For more information, please visit the IPCC website.

The most common refrigerant today, R-22, has a 100-year GWP of 1,810, almost 2,000 times the potency of carbon dioxide, so just one pound of R-22 is nearly as potent as a ton of carbon dioxide. To compare with driving a car, this means that just one 30-lb tank of R-22 is more potent if released, than the CO₂ emitted into the atmosphere by driving nearly 7 additional cars each year (source data available at CARB's CoolCalifornia Calculator).

The most common replacement for R-22 in supermarket systems, R-404A, is more than twice as potent a greenhouse gas than R-22. One small 30-lb tank holds the equivalent of the CO₂ emitted by driving more than 14 additional cars each year (see image, above). Just one single pound of R-404A is as potent as roughly two tons of CO₂. Because refrigeration systems can hold hundreds to thousands of pounds, and many of these leak at the rate of 20% or even more per year – sometimes much more – the move away from high-GWP refrigerants will slow the pace of the global warming and climate impacts already underway.

Ensuring exceptionally leak-tight systems and near-perfect reclamation, or changing course to safer alternatives in refrigeration systems, are two options for addressing the risk to the climate posed by high-GWP refrigerants. 

Be advised that common replacements for R-22, such as R-404A and R-507A, have been identified by both California and the U.S. EPA for future restrictions because of their high GWP values and the availability of alternatives that pose a lower overall risk to human health and/or the environment. In addition, national and international efforts to phase-down the global use of these and other high-GWP refrigerants may affect future price and availability. New low-GWP technologies and solutions are advancing rapidly and are available today.

Refrigerants regulated under the Refrigerant Management Program (RMP) include any refrigerant that is an ozone depleting substance (ODS) as defined in Title 40 of the Code of Federal Regulation, Part 82, and any compound with a global warming potential (GWP) value equal to or greater than 150 according to the GWPs specified in IPCC's fourth Assessment Report (AR4) of 2007.

The table below lists many common refrigerants; however it does not list all refrigerants regulated under the RMP, nor does it list all available alternatives to those refrigerants. Newer refrigerants including HFO blends may be subject to the regulation but may not yet be found on this list.

Any refrigerant not listed below must be checked to determine if it is high-GWP or an ozone depleting substance (ODS).

* GWPs listed are IPCC AR4 (2007), 100-year GWPs. By definition the RMP regulation uses these GWPs to determine if any given refrigerant is high-GWP.

Warning: in some cases high-GWP refrigerants have been advertised as "environmentally friendly" or "low-GWP" when they are in fact high-GWP and regulated under the RMP. Be sure to verify any advertised claims.