Chlorofluorocarbons (CFCs) are entirely human-made compounds of carbon, chlorine, and fluorine, once used as refrigerants and aerosol propellants, that have the highest global warming potential (GWP) of any greenhouse gas and also destroy the stratospheric ozone layer.
Chlorofluorocarbons (CFCs) are synthetic chemicals made of carbon, chlorine, and fluorine atoms. Unlike carbon dioxide or methane, there is no natural source of CFCs. Every molecule in the atmosphere came from human activity, mostly from refrigerants in air conditioners and fridges, propellants in spray cans, and industrial solvents.
For AP Enviro, CFCs matter twice. First, they're one of the five principal greenhouse gases (EK STB-4.C.1), and they're the most potent of the group. Per molecule, CFCs trap far more heat than carbon dioxide, giving them the highest global warming potential (GWP) of any greenhouse gas (EK STB-4.D.1). Second, when CFCs drift up to the stratosphere, UV radiation breaks them apart and releases chlorine atoms that destroy ozone molecules. One chemical, two separate environmental problems. That double identity is exactly what the exam likes to test.
CFCs live in Topic 9.3, The Greenhouse Effect (Unit 9: Global Change), supporting two learning objectives. Under AP Enviro 9.3.A, you need to identify the principal greenhouse gases: carbon dioxide, methane, water vapor, nitrous oxide, and CFCs. Under AP Enviro 9.3.B, you need to rank their potency. The CED gives you the order directly: CFCs have the highest GWP, then nitrous oxide, then methane, with CO2 as the baseline at a GWP of 1. That ranking is one of the most reliable multiple-choice questions in Unit 9. CFCs also tie Unit 9 together internally, since the same compound shows up in both the climate change and ozone depletion storylines, plus the Montreal Protocol, the go-to example of a successful international environmental treaty.
Global Warming Potential (GWP) (Unit 9)
GWP measures how much heat a gas traps compared to CO2, which is set at 1. CFCs sit at the top of the GWP ladder. If a question asks which gas is most potent per molecule, the answer is CFCs, even though CO2 causes more total warming because there's vastly more of it.
Ozone Layer (Unit 9)
CFCs are the main culprit behind stratospheric ozone depletion. UV light splits CFC molecules apart, freeing chlorine atoms that break down ozone in a catalytic cycle. Same molecule, completely different problem from the greenhouse effect. Don't merge the two.
Montreal Protocol (Unit 9)
The 1987 Montreal Protocol phased out CFC production worldwide, and it worked. The ozone layer is recovering. It's the exam's favorite example of international environmental policy actually succeeding, so know that CFCs are the chemical it targeted.
Residence Time (Unit 9)
Potency isn't just about heat-trapping per molecule; it's also about how long a gas sticks around. Water vapor has a short residence time, so it doesn't drive climate change (EK STB-4.C.2). CFCs persist in the atmosphere for decades, which is part of why their warming impact is so outsized.
CFCs show up most often in multiple-choice questions about greenhouse gas potency. Classic stems ask which greenhouse gas has the highest global warming potential (answer: CFCs), which gas is the GWP baseline (answer: carbon dioxide), and which greenhouse gas is most associated with ozone depletion (answer: CFCs again). You should be able to recite the GWP ranking from EK STB-4.D.1 cold. CFCs highest, then nitrous oxide, then methane, with CO2 at 1. On FRQs, CFCs can appear in questions about ozone depletion, where you'd describe how chlorine atoms catalytically destroy ozone, or in policy questions, where the Montreal Protocol is your evidence that phasing out a pollutant can work. The key skill is keeping the two CFC problems straight and naming the right one for the question being asked.
CFCs cause both problems, which is exactly why students mix them up. Ozone depletion happens in the stratosphere, where chlorine from CFCs destroys the ozone that blocks UV radiation. The greenhouse effect happens in the troposphere, where CFC molecules trap outgoing infrared heat. The ozone hole does not cause global warming, and global warming does not cause the ozone hole. They're two separate consequences of the same chemical, and the exam loves checking whether you know that.
CFCs are entirely human-made compounds of carbon, chlorine, and fluorine, with no natural sources, originally used as refrigerants, aerosol propellants, and solvents.
Among greenhouse gases, CFCs have the highest global warming potential, followed by nitrous oxide, then methane, with carbon dioxide as the baseline at a GWP of 1.
CFCs are one of the five principal greenhouse gases listed in the CED, alongside carbon dioxide, methane, water vapor, and nitrous oxide.
CFCs cause two separate problems, trapping heat in the troposphere as a greenhouse gas and destroying ozone in the stratosphere when UV light frees their chlorine atoms.
The 1987 Montreal Protocol phased out CFC production globally and is the exam's standard example of a successful international environmental agreement.
Even though CFCs are the most potent greenhouse gas per molecule, carbon dioxide drives more total warming because it's emitted in far greater quantities.
CFCs are synthetic compounds of carbon, chlorine, and fluorine that were widely used as refrigerants and aerosol propellants. In AP Enviro they're tested as the greenhouse gas with the highest global warming potential (Topic 9.3) and as the main cause of stratospheric ozone depletion.
CFCs. Per EK STB-4.D.1, the GWP order is CFCs highest, then nitrous oxide, then methane, with carbon dioxide as the reference point at a GWP of 1. This exact ranking is a common multiple-choice question.
Both, but through completely different mechanisms. As greenhouse gases, CFCs trap infrared heat in the troposphere. In the stratosphere, UV radiation breaks them apart and the freed chlorine atoms destroy ozone. Keep the two problems separate on the exam.
Entirely man-made. Unlike CO2, methane, and nitrous oxide, which have both natural and human sources, every CFC molecule in the atmosphere came from human industrial activity.
Their production has been phased out under the 1987 Montreal Protocol, which nearly every country signed. Because CFCs have long atmospheric lifetimes, molecules released decades ago are still up there, but the ozone layer is gradually recovering as concentrations fall.
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