In the early 1990's, the Global Monitoring Division of NOAA’s Earth System Research Laboratory (formerly the Climate Monitoring and Diagnostics Laboratory and now the Global Monitoring Laboratory) expanded the HATS flask sampling program to monitor atmospheric levels of chemicals used as substitutes for ozone-depleting gases being phased out by the 1987 Montreal Protocol on Substances that Deplete the Ozone Layer. This research effort, made possible in part by funds from the NOAA Climate Program Office’s AC4 program (formerly known as its Atmospheric Chemistry Project), is focused on making long-term, global-scale measurements of these chemicals and other long-lived gases in order to enable an understanding of how they influence stratospheric ozone, climate, and air quality (see the list of measured chemicals below). A primary goal of the project is to provide, through atmospheric measurements, an understanding of how policy decisions on national to international scales, natural processes, and human activities are altering the atmospheric environment in which we live.
Two primary classes of compounds encompassed by this Project include:
These chemicals represent the first- and second-generation substitutes for the most potent ozone-depleting substances. HCFCs were considered as suitable replacements, at as first-generation substitutes on a temporary basis, owing to their reduced potential to deplete stratospheric ozone. HCFCs have ozone-depletion potentials (ODPs) that are only a fraction (<15%) as large as the ODPs of CFCs. It seems that both the ready availability of HCFCs along with the development of additional alternative processes and chemicals allowed for a timely elimination of CFCs, methyl chloroform, and carbon tetrachloride in the 1990s and early 2000s.
There was concern about long term use of these alternatives, however, as HCFCs contain chlorine and this chlorine contributes to stratospheric ozone depletion. Furthermore, HCFCs are greenhouse gases. Because of this, Amendments to the Montreal Protocol include a schedule for the phase-out of HCFC production for dispersive uses. This phase-out is currently well underway. Countries operating under Article V of the Protocol (also called developing countries) capped their production of HCFCs for the first time in 2013 at levels based on their average baseline production during 2009 to 2010; in 2015 this production allotment is reduced by 10%. Production in non-Article V Parties (developed countries) has been decreasing since 2000 in accordance with the Protocol phase-out, and was scheduled to be no more than 10% of baseline magnitudes in 2015.
The non-ozone-depleting HFCs are first- and second-generation substitutes. HFC-134a replaced CFC-12 in mobile air conditioning and blends of other HFCs (e.g., HFC-125 and HFC-32) have replaced HCFCs in multiple applications. A concern associated use of long-lived HFCs arises because these chemicals are potent greenhouse gases; continued use of these gases, particularly in new emerging markets, would result in significant contribution to climate change through increased radiative forcing. HFC emissions are controlled by the Kyoto Protocol of the United Nations Framework Convention on Climate Change, but this Protocol does not prevent substantial increases in future HFC emissions. It is primarily because of concern about climate change that many Parties to the Montreal Protocol are considering an Amendment to the Montreal Protocol that would limit HFC production. The contribution of HCFCs and HFCs to radiative forcing is regularly updated and included in NOAA’s Annual Greenhouse Gas Index. Finally, a number of the HFCs, for example HFC-134a, decompose in the atmosphere and produce a long-lived chemical called trifluoroacetic acid (or TFA) that is known to have adverse effects on certain biota. In the near future the accumulation of TFA from HFC degradation is expected to be small relative to background levels in most ecosystems.
The Chlorofluorocarbon Alternatives Monitoring Project allows measurements of the global atmospheric distribution of HCFCs, HFCs, and a number of other compounds over time. Samples are currently collected throughout the entire year at continental and remote locations across the globe as part of the HATS flask sampling program. These flasks are analyzed with customized state-of-the-art instrumentation in our Boulder Laboratory. This instrumentation allows for separation and detection of components in air samples with gas chromatography and mass spectrometry techniques (GC-MS). By analyzing 0.2 L of air at a time, the abundance of these compounds is determined in air at levels as low as 1 part per 10,000,000,000,000 (0.1 part per trillion). Accurate results are obtained by comparing responses from samples to calibration gas standards prepared in the standards lab of the HATS group. The data acquired has provided a wealth of information regarding atmospheric processes, the global societal transition away from use of ozone-depleting substances, and the year to year variability of natural processes affecting the atmospheric environment.
Furthermore, along with measurements of alternatives to ozone-depleting substances, GC-MS analysis of flasks in this program has provided a wealth of unique data for other important trace gases on global and regional scales (see Highlighted findings section below). Data for CFCs and other ozone-depleting substances from flask analysis by GC-MS provide a second, quasi-independent measure of atmospheric changes for a subset of gases (CFCs, some HCFCs, and methyl halides) that are also measured by our in-situ gas chromatographs (CATS). Although flasks provide measurements with a much lower sampling frequency than on-site instrumentation, they are collected at more sites and the GC/MS instrumentation provides measurements of a larger number of chemicals. As of 2015, HATS flasks were collected at 16 stations across the globe (see Table 1 in the flask program description).
The flask sampling program also enables measurements of global distributions and trends for methyl halides, chlorinated gases with shorter lifetimes, a number of hydrocarbons including benzene, COS, and additional brominated gases such as CH2Br2 and CHBr3. Some of these gases play important roles in regulating stratospheric ozone; our flask measurements provide a wealth of unique information regarding chemical and transport processes on broad scales. This type of information will enhance our predictive capacity for understanding how these trace gases affect the chemical and radiative state of the atmosphere and its change over time.
In 2004, a program was initiated to allow samples regularly collected from aircraft profiles and tall towers as part of the CCGG participation in the North American Carbon Program to be regularly analyzed in the HATS group. Initially, samples were analyzed on the CAMP GC/MS, but by 2007 additional funding had enabled the construction of second instrument dedicated to analyzing flasks collected by these programs. Thousands of flask samples collected as part of this program, primarily daily flasks collected at approximately 10 tower sites across the U.S., are analyzed each year. The high-frequency and high-density data from this network is unprecedented and provides unique insights into terrestrial (and national) emissions and uptake of the full suite of gases being measured by GC/MS. In 2014 a new instrument (Perseus 1) was constructed to also contribute to the analysis of flask samples collected in these programs.
Data collected as part of the CAMP have yielded many insights into the workings of the atmosphere and the role of international policy on the chemical state of the atmosphere. Some highlights:
Links to measurement data and post-script figures from GML made by CAMP and other programs at GML:
(The Chlorofluorocarbon Alternatives Monitoring Project is part of the Flask Sampling Program of the Halocarbons and other Atmospheric Trace Species Group (HATS) of GML)
Project Leader: Dr. Stephen A.
Montzka; phone: (303)-497-6657.
Updated June 2015