Global Warming Potential, 100-year time horizon Likewise, methane is responsible for a large portion of recent warming despite having a GWP much lower than several other greenhouse gases because emissions have increased drastically.įifth Assessment Report (Intergovernmental Panel on Climate Change, 2014). These values are periodically updated by the scientific community as new research refines estimates of radiative properties and atmospheric removal mechanisms (sinks) for each gas.ĭespite carbon dioxide’s comparatively low GWP among major greenhouse gases, the large human-caused increase in its atmospheric concentration has caused the majority of global warming. The table below presents atmospheric lifetime and GWP values for major greenhouse gases from the Fifth IPCC Assessment Report (AR5) released in 2014. A gas with a long lifetime, but relatively low radiative efficiency, may end up exerting more warming influence than a gas that leaves the atmosphere faster than the time window of interest but has a comparatively high radiative efficiency, and this would be reflected in a higher GWP. Gases with high GWPs will warm the Earth more than an equal amount of CO 2 over the same time period. This is often calculated over 100 years, though it can be done for any time period. the strength of their greenhouse effect) of each unit of gas (by weight) over a specified period of time, expressed relative to the radiative effect of carbon dioxide (CO 2). These characteristics are incorporated in the Global Warming Potential (GWP), a measure of the radiative effect (i.e. The second is the atmospheric lifetime, which measures how long the gas stays in the atmosphere before natural processes (e.g., chemical reactions) remove it. The first is their ability to absorb energy and radiate it (their “radiative efficiency”). Two characteristics of atmospheric gases determine the strength of their greenhouse effect. Small changes in the atmospheric concentration of these gases can lead to changes in temperature that make the difference between ice ages when mastodons roamed the Earth, and the sweltering heat in which the dinosaurs lived. Multiple gases contribute to the greenhouse effect that sets Earth’s temperature over geologic time.
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