The Advanced Atmospheric Gases Experiment (AGAGE)

The Advanced Atmospheric Gases Experiment (AGAGE) measures all important greenhouse gases (GHGs) and ozone depleting substances (ODSs) in the global atmosphere

AGAGE measures synthetic greenhouse gases (GHGs) and ozone depleting substances (ODSs) at 13+ sites around the world. Measurement sites are operated by SIO and many international partners. The central AGAGE experimental and calibration laboratory is located at Scripps Institution of Oceanography at the University of California, San Diego.

Climate impact (radiative forcing) from greenhouse gases (GHGs)

The impact of greenhouse gases in the atmosphere on climate is often expressed using its radiative forcing (RF). RF basically expresses how much more (or less) energy (from the sun) is trapped in the atmosphere due to the presence of a certain greenhouse gas (compared to the pre-industrial atmosphere).
Total radiative forcing (RF, W/m²), or the impact on the climate, of all greenhouse gases (GHGs) is dominated by carbon dioxide (CO₂), followed by methane (CH₄), the sum of all ozone depleting substances (ODSs), nitrous oxide (N₂O), and the sum of all synthetic GHGs.
(ODSs are gases that contain chlorine and/or bromine atoms. They are causing ozone depletion including the "ozone hole" in the Southern Hemisphere every austral spring. Synthetic GHGs are mostly man-made - that is they are mostly not natural.)
Several ozone depleting substances (ODSs) are also strong GHGs, foremost the chlorofluorocarbons (CFCs). While HFCs are generally less strong GHGs than CFCs, their contribution to RF is increasing rapidly due to their widespread use and emissions. (In other words, once CFCs were found to be destroying the stratospheric ozone layer, they (and other compounds) have been phased out. Often times they were replaced by HCFCs and HFCs, sometimes by other means. This replacement protected the ozone layer and also had a positive impact of the climate. Initially a reduction in combined RF was achieved, but the sharp increase of the HFCs in the atmosphere threatens to erode this benefit to the climate.)

Chlorine and bromine from ozone depleting substances (ODSs)

To understand ozone depletion in the stratosphere, it is important to understand the amounts of chlorinated and brominated compounds emitted into the atmosphere as they supply the chlorine and bromine needed for catalytic ozone depletion in the stratosphere.
Equivalent chlorine (ECl) is a measure of how much chlorine and bromine is contained in halogenated compounds which are present in the troposphere (lower atmosphere). Equivalent chlorine is important to understand how much of these compounds can get into the stratosphere and contribute to ozone depletion. Many of these compounds are man-made and are emitted into the troposphere due to industrial activities. ECl is based on the abundances of all halogenated ODSs measured by AGAGE.
The use of methyl bromide (CH₃Br) as fumigant (against pests) has been substantially reduced in recent years so that most of its present impact is due to natural sources. Methyl chloride (CH₃Cl) is largely emitted from natural sources.

(Note, that the impact of brominated and chlorinated very short lived substances (VSLS) cannot be adequately reflected in the ECl plot, but they significantly contribute to ozone depletion due to emissions in regions where fast convective processes occur. AGAGE measures several of these VSLSs, but the measurements are currently not shown here.)

Equivalent effective stratospheric chlorine (EESC) is a measure of how much chlorine and bromine (originating from the ozone depleting substances (ODSs) in the troposphere) is available for ozone depletion in the stratosphere.
Due to the phase-out of production and consumption of (most) Ozone Depleting Substances (ODSs) mandated by the Montreal Protocol on Substances that Deplete the Ozone Layer, EESC is slowly decreasing. This will eventually allow the ozone layer to recover and prevent the annual Antarctic (and the occasional Arctic) "ozone hole" from opening.
The process is slow and needs to be monitored to detect new emissions of ODSs, which could threaten this recovery. Examples of threats to ozone layer recovery are the recently discovered new CFC-11 emissions and the increasing emissions of several VSLS (stemming from their use as solvents and/or feedstock to produce other chemicals).

AGAGE global measurements of CFCs

Measurement data for these and other GHGs and ODSs can be found here (data portal).

CFCs have contributed to stratospheric ozone depletion and their use is the main reason for the annual Antarctic "ozone hole". Therefore, production and consumption of CFCs have been phased-out by the Montreal Protocol on Substances that Deplete the Ozone Layer to reduce the size of annual Antarctic "ozone hole" and to allow the ozone layer to eventually recover. Large "banks" of CFCs still exist, for example in old refrigerators and insulation foams where CFCs were used. Moreover, several CFCs have very long atmospheric lifetimes, so that they are only very slowly removed from the atmosphere.

AGAGE global measurements of chlorinated species

Measurement data for these and other GHGs and ODSs can be found here (data portal).

Production and consumption of CH₃CCl₃ and CCl₄ have been phased-out by the Montreal Protocol on Substances that Deplete the Ozone Layer to reduce the size of annual Antarctic "ozone hole" and to allow the ozone layer to eventually recover. CH₃CCl₃ has been a real success, it has almost disappeared from the atmosphere due to its short atmospheric lifetime and reduced emissions, but many sources of CCl₄ emissions still exist as evident from a slower than expected atmospheric decline.
The other compounds shown below are not regulated by the Montreal Protocol on Substances that Deplete the Ozone Layer due to their short atmospheric lifetime and/or predominantly natural original. However, atmospheric abundances of CHCl₃ and CH₂Cl₂, two chlorinated very short-lived substances (VSLS), are on the rise, most likely due to industrial activities.

AGAGE global measurements of halons and methyl bromide

Measurement data for these and other GHGs and ODSs can be found here (data portal).

Production and consumption of the halons, used as fire fighting compounds, and the use of methyl bromide as fumigant are regulated by the Montreal Protocol on Substances that Deplete the Ozone Layer to reduce the size of annual Antarctic "ozone hole" and to allow the ozone layer to eventually recover. The halons have been and are still being used as fire fighting compounds. Large "banks" of them still exist in fire fighting equipment. Halons are very strong ozone depleters.

AGAGE global measurements of (major) hydrochlorofluorocarbons (HCFCs)

Measurement data for these and other GHGs and ODSs can be found here (data portal).

Hydrofluorocarbons (HCFCs) have been as used as first generation replacements for CFCs in many application as they contribute less to ozone depletion in the stratosphere (upper atmosphere) due to their generally shorter lifetimes in the troposphere (lower atmosphere). Production and consumption of HCFCs is currently also being phased-out by the Montreal Protocol on Substances that Deplete the Ozone Layer to reduce their contribution to stratospheric ozone depletion. The Montreal Protocol mandates a 100% HCFC reduction in developed countries by 2020 and a 67.5% HCFC reduction in developing countries by 2025 and 100% by 2030. Large "banks" of HCFCs in old equipment and foams exist.

AGAGE global measurements of (major) hydrofluorocarbons (HFCs)

Measurement data for these and other GHGs and ODSs can be found here (data portal).

Hydrofluorocarbons (HFCs) have replaced CFCs and HCFCs in many industrial applications. HFCs do not contribute to ozone depletion, but are also quite strong greenhouse gases. The reduction of CFC emissions to protect the ozone layer has had a strong co-benefit of reducing the impact on the climate, as CFCs are very strong GHGs. However, this climate benefit of the Montreal Protocol is being eroded due to the sharp rise of HFC abundances in the atmosphere. Therefore, phase-out schedules for production and consumption of HFCs have recently been added to the Montreal Protocol on Substances that Deplete the Ozone Layer in the Kigali Amendment to reduce the impact of these replacement compounds on the climate.

HFC-23 is a special case as most of its emissions stem from the production of HCFC-22, not from intentional use or application as in the case of the other HFCs. HFC-23 emissions could be avoided almost completely. To reduce the impact of this very strong GHG on the climate, emissions of HFC-23 are now regulated by the Kigali Amendment to the Montreal Protocol.

AGAGE global measurements of PFCs, NF₃, SF₆ and SO₂F₂

Measurement data for these and other GHGs and ODSs can be found here (data portal).

PFCs, SF₆ and NF₃ have atmospheric lifetime of hundreds to tens of thousands of years and their presence in the atmosphere increases the amount of energy absorbed from incoming sunlight for generations to come.
Emissions of these compounds arise from several important industrial activities, such as aluminum production, semiconductor production, and electricity transfer. Efforts to reduce these emissions are under way, but atmospheric abundances keep increasing.
Sulfuryl fluoride (SO₂F₂) has a relatively short atmospheric lifetime as it hydrolyzed in the ocean. It is used to replace the ozone depleting methyl bromide (CH₃Br) in fumigation applications against various pests.