JENS MUHLE

Researcher
Geosciences Research Division

Research Interests

  • AGAGE (Advanced Global Atmospheric Gases Experiment) (data portal)
  • Global Warming, Climate Change, Greenhouse Gases (GHGs)
  • Stratospheric Ozone Depletion, Ozone Depleting Substances (ODSs)
  • Global and regional emissions, loss processes, and lifetimes of ODSs and GHGs
  • Top-down (measurement based) verification of bottom-up emission estimates
  • Top-down (measurement based) verification of compliance with the Montreal Protocol on Substances that Deplete the Ozone Layer and the Paris Agreement
  • Halogenated trace gases
  • Perfluorinated Compounds (PFCs) and their emissions from global aluminium, rare-earth, and semi-conductor industries
  • Trace gas measurement techniques (GC-FID/ECD, GC/MSD, GC/TOF-MS, PTR-TOF-MS, CRDS)
  • Atmospheric chemistry
  • Wildfire emissions
  • Long-range transport of pollutants

Degrees

  • Diploma in Chemistry, University of Wuppertal
  • Doctor of Natural Sciences, Max Planck Institute for Chemistry, Mainz and Johannes Gutenberg University Mainz, Germany

AGAGE global network

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.

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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.
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.)

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Total radiative forcing (RF) (left top) and contribution from individual compounds classes: CO2 (carbon dioxide) (left middle), CH4 (methane), (Total) ODSs (ozone depleting substances), N2O (nitrous oxide), and (Total) Synthetic GHGs (left) (left bottom).
(Total) ODS as the sum of RF from CFCs (chlorofluorocarbons), HCFCs (hydrochlorofluorocarbons), solvents (chlorinated solvents and feedstock compounds), and halons (brominated fire fighting compounds) (right top).
Total Synthetic GHGs as the sum of RF from PFCs (perfluorocarbons), HFCs (hydrofluorocarbons), SF6 (sulfur hexafluoride), SO2F2 (sulfuryl fluoride), NF3 (nitrogen trifluoride) (right bottom).

This plot and the following stack plots were produced by CSIRO, one of our many international partners.

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Contribution of individual compound groups to total radiative forcing (RF) on a logarithmic scale: CO2 (carbon dioxide), CH4 (methane), (Total) ODSs (ozone depleting substances), CFCs (chlorofluorocarbons), N2O (nitrous oxide), HCFCs (hydrochlorofluorocarbons), CH3CCl3, CCl4 , Kyoto Protocol Synthetics, PFCs (perfluorocarbons), HFCs (hydrofluorocarbons), SF6 (sulfur hexafluoride), halons (brominated fire fighting compounds), SO2F2 (sulfuryl fluoride), NF3 (nitrogen trifluoride).

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Radiative forcing (RF) from CFCs (chlorofluorocarbons), HCFCs (hydrochlorofluorocarbons), HFCs (hydrofluorocarbons), and other synthetic greenhouse gases (SGHGs, SF6 (sulfur hexafluoride), PFCs (perfluorocarbons), halons, CH3CCl3 and CCl4).
Several CFCs still contribute significantly to total RF, even though their production and consumption has been phased out by the Montreal Protocol on Substances that Deplete the Ozone Layer. This lasting contribution of CFCs to RF is in part due their long atmospheric lifetimes and in part due to large "banks" (old insulation foams, refrigerators etc.), from which these compounds are still leaking into the atmosphere. The growth in the contribution of HCFCs to RF has slowed down as consumption and production of HCFCs are being phased out by the Montreal Protocol on Substances that Deplete the Ozone Layer. In contrast, the contribution of HFCs to RF is increasing unabated, which is why HFCs have recently been added to the Montreal Protocol on Substances that Deplete the Ozone Layer in the Kigali Amendment.

Chlorine and bromine from ozone depleting substances (ODSs)

To understand ozone depletion in the stratosphere, it is important to understand how many chlorinated and brominated compounds are emitted into the atmosphere as they supply the chlorine and bromine needed for catalytic ozone destruction 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 mostly of natural sources as well.

(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. AGAGE measures several of these VSLSs, but the measurements are currently not shown here.)
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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 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 would threaten this recovery.
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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, which makes them disappear only very slowly from the atmosphere.

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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.

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Note, PCE data is reported on a calibration scale adopted from the National Oceanographic and Atmospheric Administration ( NOAA HATS).

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.

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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.

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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.

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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 hydrolysis in the ocean. It is used to replace the ozone depleting methyl bromide (CH3Br) in fumigation applications against various pests.

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