Decision Maker’s Toolbox: The Annual Greenhouse Gas Index

Decision Maker’s Toolbox: The Annual Greenhouse Gas Index


Climate change is a complex subject. But one of the things we’re sure about is that humans are releasing gases that increase the heat load of the atmosphere and the ocean. NOAA’s Earth System Research Lab provides a simple means of evaluating the direct effect of greenhouse gas emissions in our warming world – the Annual Greenhouse Gas Index. The Greenhouse Gas Index is a measure of the climate-warming influence of a suite of greenhouse gases that we measure in the atmosphere routinely over decades. They’re composed primarily of carbon dioxide, methane, nitrous oxide, chlorofluorocarbons, other gases. Mainly CO2 is driving the Annual Greenhouse Gas Index increase that we see today. Using 1990 as a baseline, the index shows the warming influence from greenhouse gases; which gases contribute most to the change each year; and variations in those influences. NOAA measures greenhouse gases around the globe. And each gas has its own story. The growth rate of methane declined after the former Soviet Union collapsed, leading to a plateau as natural gas exploration tapered. Notice the increase as both the Russian economy expanded and the Earth system released more methane, especially in the tropics. Since the Montreal Protocol went into effect in 1989, emissions of chlorofluorocarbons, also known as CFCs, decreased. This had two important effects. In addition to helping the ozone problem, the treaty prevented additional warming Carbon dioxide is responsible for most of the greenhouse gas warming influence since pre-industrial times. Recently, carbon dioxide has accounted for more than 80 percent of the annual growth of this forcing. Since 1990, global emissions have turned up the warming influence by over 30 percent. The Annual Greenhouse Gas Index synthesizes the highest quality atmospheric observation data from around the globe and therefore contains little uncertainty. It’s a reliable indicator of the influence of greenhouse gas emissions on the global climate system. One analogy I like to use is lying in bed, comfortable with your electric blanket and you decide to start turning the dial up. And when you first start turning it up, you think, “Gee! I still feel OK, everything’s just fine.” And you keep turning it up. Then you realize, “Gee, I’m getting a little bit warmer”, and so you still keep turning it up. And finally you say, well no, I’m gonna stop now, but you keep getting warmer, for quite a while, until it finally reaches an equilibrium state. What the AGGI is, it’s essentially the dial on your electric blanket. This tells us what we’ve committed on a long-term basis to climate change.

Leave a Reply

Leave a Reply

Your email address will not be published. Required fields are marked *