CFC’s may stay in atmosphere less than previously thought
Image: Britannica
MIT scientists have found that ozone-depleting chlorofluorocarbons, or CFCs, stay in the atmosphere for a shorter amount of time than previously estimated. Their study suggests that CFCs, which were globally phased out in 2010, should be circulating at much lower concentrations than what has recently been measured.
The new results, published today in Nature Communications, imply that new, illegal production of CFCs has likely occurred in recent years. Specifically, the analysis points to new emissions of CFC-11, CFC-12, and CFC-113. These emissions would be in violation of the Montreal Protocol, the international treaty designed to phase out the production and consumption of CFCs and other ozone-damaging chemicals.
The current study’s estimates of new global CFC-11 emissions is higher than what previous studies report. This is also the first study to quantify new global emissions of CFC-12 and CFC-113.
“We find total emissions coming from new production is on the order of 20 gigagrams a year for each of these molecules,” says lead author Megan Lickley, a postdoc in MIT’s Department of Earth, Atmospheric, and Planetary Sciences. “This is higher than what previous scientists suggested for CFC-11, and also identifies likely new emissions of CFC-12 and 113, which previously had been overlooked. Because CFCs are such potent greenhouse gases and destroy the ozone layer, this work has important implications for the health of our planet.”
The study’s co-authors include Sarah Fletcher at Stanford University, Matt Rigby at the University of Bristol, and Susan Solomon, the Lee and Geraldine Martin Professor of Environmental Studies in MIT’s Department of Earth, Atmospheric and Planetary Sciences.
Banking on lifetimes
Prior to their global phaseout, CFCs were widely used in the manufacturing of refrigerants, aerosol sprays, chemical solvents, and building insulation. When they are emitted into the atmosphere, the chemicals can loft to the stratosphere, where they interact with ultraviolet light to release chlorine atoms, the potent agents that erode the Earth’s protective ozone.
Today, CFCs are mostly emitted by “banks” — old refrigerators, air conditioners, and insulation that were manufactured before the chemical ban and have since been slowly leaking CFCs into the atmosphere. In a study published last year, Lickley and her colleagues calculated the amount of CFCs still remaining in banks today.
They did so by developing a model that analyzes industry production of CFCs over time, and how quickly various equipment types release CFCs over time, to estimate the amount of CFCs stored in banks. They then incorporated current recommended values for the chemicals’ lifetimes to calculate the concentrations of bank-derived CFCs that should be in the atmosphere over time. Subtracting these bank emissions from total global emissions should yield any unexpected, illegal CFC production. In their new paper, the researchers looked to improve the estimates of CFC lifetimes.
“Current best estimates of atmospheric lifetimes have large uncertainties,” Lickley says. “This implies that global emissions also have large uncertainties. To refine our estimates of global emissions, we need a better estimate of atmospheric lifetimes.”
Updated spike
Rather than consider the lifetimes and emissions of each gas separately, as most models do, the team looked at CFC-11, 12, and 113 together, in order to account for similar atmospheric processes that influence their lifetimes (such as winds). These processes have been modeled by seven different chemistry-climate models, each of which provides an estimate of the gas’ atmospheric lifetime over time.
“We begin by assuming the models are all equally likely,” Lickley says. “Then we update how likely each of these models are, based on how well they match observations of CFC concentrations taken from 1979 to 2016.”
After including these chemistry-climate modeled lifetimes into a Bayesian simulation model of production and emissions, the team was able to reduce the uncertainty in their lifetime estimates. They calculated the lifetimes for CFC-11, 12, and 113 to be 49 years, 85 years, and 80 years, respectively, compared with current best values of 52, 100, and 85 years.
“Because our estimates are shorter than current best-recommended values, this implies emissions are likely higher than what best estimates have been,” Lickley says.
To test this idea, the team looked at how the shorter CFC lifetimes would affect estimates of unexpected emissions, particularly between 2014 and 2016. During this period, researchers previously identified a spike in CFC-11 emissions and subsequently traced half of these emissions to eastern China. Scientists have since observed an emissions decrease from this region, indicating that any illegal production there has stopped, though the source of the remaining unexpected emissions is still unknown.
When Lickley and her colleagues updated their estimates of CFC bank emissions and compared them with total global emissions for this three-year period, they found evidence for new, unexpected emissions on the order of 20 gigagrams, or 20 billion grams, for each chemical.
The results suggest that during this period, there was new, illegal production of CFC-11 that was higher than previous estimates, in addition to new production of CFC-12 and 113, which had not been seen before. Together, Lickley estimates that these new CFC emissions are equivalent to the total yearly greenhouse gas emissions emitted by the United Kingdom.
It’s not entirely surprising to find unexpected emissions of CFC-12, as the chemical is often co-produced in manufacturing processes that emit CFC-11. For CFC-113, the chemical’s use is permitted under the Montreal Protocol as a feedstock to make other chemicals. But the team calculates that unexpected emissions of CFC-113 are about 10 times higher than what the treaty currently allows.
“With all three gases, emissions are much lower than what they were at their peak,” Lickley says. “But they’re very potent greenhouse gases. Pound for pound, they’re five to 10,000 times more of a global warming chemical than carbon dioxide. And we’re currently facing a climate crisis where every source of emission that we can reduce will have a lasting impact on the climate system. By targeting these CFCs, we would essentially be reducing some contribution to climate change.”
This research was supported in part by VoLo Foundation.
See more here: mit.edu
PSI editor’s note: We at Principia Scientific International do not believe there is a climate crisis, nor do we endorse the views about ‘greenhouse gases’ in this article.
Please Donate Below To Support Our Ongoing Work To Defend The Scientific Method
PRINCIPIA SCIENTIFIC INTERNATIONAL, legally registered in the UK as a company 
incorporated for charitable purposes. Head Office: 27 Old Gloucester Street, London WC1N 3AX.
Herb Rose
| #
CFC s are made with Chlorine and Florine because these elements are stronger oxidizers than oxygen making them non flammable (they can’t be oxidized by oxygen). they do not destroy the ozone in the ozone layer. Ozone is an unstable molecule that spontaneously decomposes without either CFC s or ultraviolet light. The ozone in the ozone layer is created when O2 molecules split from absorbing more than 450,000 joules/mole of energy and an oxygen atom combines with an oxygen molecule. It is the N2 and O2 in the atmosphere that are absorbing uv, not ozone! (At a concentration of 10 ppm there isn’t enough ozone in the layer to absorb anything.) The ozone thinning (“hole”) is a result of less uv coming from the sun. Hence the larger the “hole” the less uv reaches the surface of the Earth.
The large mass of the CFC s makes it impossible for them to be lifted through the troposphere into the stratosphere. The CFC s found there and their increasing amount is from them being used as thruster fuel to adjust the orbits of spy satellites as they pass over the poles.
Alan
| #
I thought CFCs were classed as dangerous because the patent was running out, so they had to be banned. It was all about money.
tom0mason
| #
As pointed out at http://cfc.geologist-1011.net/ not all CFC are man-made by are reaction products from volcanoes.
Charles Higley
| #
There is nothing wrong with studying the time course of CFCs in the atmosphere. But, why are they still touting or claiming that CFCs destroy ozone? Do they not read?
The ozone scare regarding CFCs was cobbled up in a report by a Dupont Chemical scientist, a report fabricated to demonize Dupont’s out-of-patent refrigerant that was now then being made cheaply brothers. With cheaper refrigerant, refrigeration became more affordable around the world and the food supply increased due to lower spoilage.
Then, Dupont went to Congress with their false report and got the ball rolling. The UN jumped in and CFCs were banned, the Montreal Protocol. It just so happened that Dupont had a new refrigerant, HFC, ready to roll and much more expensive.
A few years after the HFC patent expired 17 years later, two things happened.
First, Dupont started to demonize HFC with the goal of having it banned, and likely with another patented, expensive replacement in place.
Second, the scientist (using the term loosely here) who made the original false report came forward and admitted the fraud.
We know now that it is the low temperatures, solar UV radiation, and nitrogen gas in the atmosphere break down ozone. It was never CFCs or HFCs.
On the upside, thermodynamic physicists have been unable to make CO2 warm anything, simply does not work. In the process, they have discovered that, between is radiative character, which is always aiming to cool things to -80 deg C, and it’s gas-liquid phase character, CO2 is basically the best refrigerant in the world. It is also nontoxic, plant food, cheap, and nonflammable, wins in every way. Mercedes Benz is using CO2 in their current auto A/C and a number of new skating rinks use CO2 only. It has been used as a secondary refrigerant for years but has not been fully appreciated until recently.
There is literally no downside to CO2. If anything it serves to cool the atmosphere at night and does nothing during daylight being saturated with in and out energies being equal.
T. C. Clark
| #
The LHC at CERN requires a lot of refrigeration….they were looking at HFO in 2019 as a gas for cooling… a search for CLOUD at CERN and HFC’s did not produce a study…the CLOUD chamber would seem to be a machine to test how HFC’s affect the atmosphere and ozone.