Climate Change in a Can

A few years ago I was cleaning out my dad’s shed, turning up all manner of nasty looking old cans of paint and solvents to dispose of. Then at some point I came upon this smallish harmless-looking canister.

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A can of Freon-12, full of climate change.

It contains a chemical called CFC-12 (tradename “Freon-12”), commonly sold until the mid-90’s as a refrigerant fluid for use in home and car air conditioners. Though it used to be sold as just another ordinary consumer product, its effect on the environment is anything but hum-drum: Among its several claims to fame, CFC-12 is one of the most potent greenhouse gases known to man. According to my own rough calculations, if you were to puncture this can and release its contents it would have the same impact on the global climate as if you had been commuting to work 30 miles each way in a standard car, five days a week — for a year.

In other words, the climate-change impact of the release of a few ounces of CFC-12 is the equivalent of roughly 500 gallons of gasoline burned and released as CO2. The outsized effect of this wicked gas is due to its high global warming potential, a bit less than 11,000 times the equivalent amount of CO2. How is it possible for a single can to contain such a staggeringly concentrated climate impact? It’s comes down to a difference in heat absorbing efficiency and persistence in the atmosphere.

We term CO2, the main cause of human-created climate change, a “greenhouse gas” because, like the glass panels in a greenhouse, it allows sunlight to reach the earth but prevents heat from escaping. CO2 behaves in this way because, by its chemical nature, it absorbs some of the infrared energy (“heat”) trying to escape the earth into space. Charged with this extra energy, the CO2 can transfer that heat back down onto the surface or to the rest of the atmosphere, causing the global temperature in aggregate to rise. Some gases, like CFC-12, are even more efficient than CO2 on a molecule-to-molecule basis at absorbing infrared energy, making them relatively more potent greenhouse gases.

That potency is also a matter of persistence. As a naturally occurring compound, CO2 finds itself involved in a host of natural reactions – including dissolving in the oceans, and acting as food for plants in photosynthesis, from there being incorporated into all the molecules that make up other living things (just remember – CO2 is what you’re built of!). The chemical gregariousness of CO2 means a molecule of it doesn’t stick around on its own in the atmosphere for extraordinary lengths of time before being seduced into some other relationship elsewhere, safely away from the atmosphere.

CFC-12 on the other hand is an entirely synthetic chemical – it only occurs on earth because humans have made it, and was designed specifically to be very stable and difficult to break down. This stability was a feature: Without CFCs, refrigerators have to use substitute chemicals like ammonia (found in floor cleaner) or other compounds that may be caustic, flammable, toxic – not at all inert, and as a result not entirely benign to use around humans. The chlorofluorocarbons like CFC-12, are in contrast really quite hard to hurt yourself with. A by-product of this in-built stability, however, is that CFCs are extremely persistent in the environment. Once released into the atmosphere, the average molecule of CFC can float around up there for hundreds to thousands of years. That’s another reason why its potential climate changing effect is so high – once released, it’s there a long while to do its work.

The climate impact of CFCs aside, their invention allowed for a safer solution to operating refrigerators (and plenty of other uses), and they worked quite well. However, you won’t find its like in the shops today (though people still seem to be trading “vintage” cans of CFCs around on ebay still). The can I found was purchased at our local drug store probably back in the mid-1990’s, back when the U.S. didn’t have any meaningful climate change policy (still don’t!). Why the disappearance?

Starting in 1991, CFCs began to depart store shelves in response to the UN’s Montreal Protocol, which called for their production and use to be entirely phased out worldwide. Their blacklisting was a consequence of another of their infamous environmental calling cards: CFCs are the main agents responsible for destroying the ozone layer, creating the ozone “holes” over the north and south poles every spring.

Southern ozone hole, October 2013. Source: NASA.

Luckily, the Montreal Protocol has been extremely effective at eliminating the release of any more CFCs, and former Secretary-General Kofi Annan has called it, “perhaps the single most successful international agreement to date”. But though emissions have been very nearly non-existent for some 20 years, most of the CFCs released are still up there in the atmosphere. Long since retired from their work in the air conditioners of yesteryear, CFCs are still detectable everywhere on our planet as a faint part-per-trillion whisp – still up there eating away the ozone layer while changing the climate. The seeming lack of improvement post-ban is a result, again, of the maddening persistence of this chemical tar-heel.

(It’s worth pointing out here that the levels of many CFCs are slowly beginning to drop, and NASA recently announced that the southern ozone hole has lately shrunk down to levels not seen since 1988. It could still take until the 2070’s though before the damage is completely reversed.)

The rise, and very slow fall, of some of the CFCs banned by the Montreal Protocol. (Though also banned, CCl4 is not technically a CFC, and SF6 was not covered under the protocol.) Source: NOAA

In looking at this can I am reminded of the discomfiting book The World Without Us, a rumination on the durability of some of our human artifacts. The author, Alan Weisman, surmises that one of the last detectable traces of human existence on the planet, should we ourselves suddenly disappear, will likely be some of the esoteric synthetic chemicals we will leave behind. Some compounds, like the PCBs, long since buried in deep ocean sediments and essentially immortal, will be present on earth for tens of thousands of years after we are gone (or at least stop producing them). Our lasting monument, a thin whiff of oily chemistry.

There is a certain irony in our chemical legacy, a tragedy of unintended consequences. The invention of these substances solved definitive problems that concretely benefited people – for instance, the very effective insecticide DDT helped eliminate mosquito borne diseases like malaria from much of the developed world, and CFCs provided a means of offering safer refrigeration to the masses (and don’t get me started on leaded gasoline). Yet the more enduring effect of these chemicals will likely be not only their continued presence long into the future, but the long-lasting environmental damages they have wrought – the near extinction of many of our most beloved birds, in the case of DDT, and the destruction of the ozone layer that protects us all from skin cancer (with climate change to boot), in the case of CFCs.

One of the first modern “environmentalist” books, documenting the disappearance of birds due to DDT exposure.

But this is life in the Anthropocene – the current epoch on earth in which humans wield a global and long-lasting influence, carrying with it a responsibility to look further down the road than we are accustomed. At this stage in our history the evidence of the works of people are everywhere, no matter how remote the place. Like Bill McKibben’s distant whine of a chainsaw in the darkest woods, in the atmosphere at least is always a faint reminder that no part of our small blue planet remains entirely “wild” or untouched.

The can of CFC-12 and an accompanying informational poster are on display in the first floor of 675 Commonwealth Ave. at the Department of Earth and Environment, Boston University.
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