Earth System Research Laboratory Global Monitoring Division

Monitoring the Changing Atmosphere

What does the ESRL Global Monitoring Division do for the nation?

The Global Monitoring Division (GMD) conducts long-term measurements of atmospheric components that are capable of forcing global climate change or depletion of the Earth’s protective ozone layer, as well as solar and terrestrial radiation. GMD monitors atmospheric parameters continuously, from a period of decades to centuries. Parameters monitored include greenhouse gases, aerosol particles, ozone, ozone-depleting gases, and solar and terrestrial radiation at global sites, including five Baseline Observatories. The observatories at Mauna Loa, Hawaii, and at the South Pole have been in operation since 1957, and the Mauna Loa carbon dioxide record is considered one of the most important, long-term geophysical records. The other observatories are located in Barrow, Alaska; Trinidad Head, California; and Cape Matatula, Island of Tutuila, American Samoa.

Recent Accomplishments

Through carbon dioxide analysis of samples from the Division’s 65 site Global Air Sampling Network, the Division established that forests and agriculture in North America may be sequestering a sizable fraction of the carbon dioxide produced by fossil fuel combustion in the U.S. The Division also determined that year-to-year variations in carbon dioxide uptake are likely related to terrestrial processes involving forests and agriculture. Payoffs: This finding opens possibilities that forestry and agricultural practices could be modified to reduce the rate of the global carbon dioxide increase, and especially that share attributed to the U.S.
Through precise measurements of global atmospheric methane, the secondmost influential greenhouse gas after carbon dioxide, GMD has shown that the rate of methane increase has slowed considerably from rates in the 1980’s. Payoffs: This observation suggests that, at least in the short run, the increase in total radiative forcing by greenhouse gases may not be as large as projected.
Through regular global measurements of the important chlorine-bearing and bromine-bearing gases that deplete the ozone layer, the Division established that total chlorine and bromine levels are now slowly decreasing in the lower atmosphere. Payoffs: This indicates that stratospheric ozone depletion should begin to decrease early in this century, lessening human exposure to harmful ultraviolet radiation and, consequently, affirming the effectiveness of international regulations on ozone-depleting substances. Key scientific input to global agreements such as the Montreal Protocol stemmed from ESRL’s research on the ozone layer and on ozonedepleting chemicals.
From measurements in the Atlantic, Pacific, and Southern Oceans, the Division demonstrated that the global oceans are a major net sink for atmospheric methyl bromide (CH3Br), an ozone-destroying compound used extensively in agriculture for fumigation. Payoffs: These measurements significantly improved our understanding of the behavior of this gas in nature, enhancing the scientific community’s ability to better distinguish between the natural and human contributions to the atmospheric burden of this important ozone-depleting gas.

What's next for the Global Monitoring Division?

The need for monitoring of atmospheric constituents that cause climate forcing (warming or cooling) is expected to grow dramatically in the future. The growing demand for global carbon dioxide data requires the expansion of the 65-site cooperative global air sampling network. In response, with funding from the President’s Climate Change Research Initiative, the Division is building an Atmospheric Carbon Cycle Observing System, concentrating on the U.S., using instrumented small aircraft and tall communication towers. When completed, the observing system will reduce uncertainty in the North American carbon uptake and provide U.S. regional carbon emission and uptake data to policy makers. The NOAA Strategic Plan and the Climate Change Science Program (CCSP) recognize the importance of reducing the uncertainty in the U.S. terrestrial carbon sink through their performance measures and Synthesis Assessment Products.

Continued monitoring of the trends in the chlorine- and bromine-bearing compounds that deplete the ozone layer is important to tracking the effectiveness of the Montreal Protocol on the Ozone Layer. Therefore, continued global monitoring of these ozone-depleting compounds and ozone itself remain priorities for the ESRL Global Monitoring Division and the CCSP Strategic Plan.

Activities in air-quality monitoring are expected to increase because future effluents from expanding Asian economies are projected to continue to increase. Currently, the Division stations at Mauna Loa, Hawaii and Barrow, Alaska regularly measure high concentrations of air pollution from Asia. Because of possible ramifications of this pollution for federal and state air-quality standards, particularly standards of western coastal states, the Division established a Baseline Station at Trinidad Head, California and is expanding its measurement programs off the east coast of Asia. Furthermore, the Division will continue to conduct weekly, airborne, vertical profiles of trace gas and ozone concentrations upwind of the California coast near Trinidad Head.

Research Partnerships

The Division has joint research projects with the other ESRL Divisions, such as integrated field studies associated with GMD’s monitoring sites or using GMD’s monitoring methods. The Division also has research partnerships with federal agencies such as NASA, the Department of Energy, the Environmental Protection Agency, the U.S. Geological Survey and 16 universities in the U.S., and maintains cooperative greenhouse gas sampling and/or ozone monitoring projects in 20 states and 37 foreign countries. The Division also has working agreements with the United Nations Environment Program and the World Meteorological Organization.