Recorded presentationJ5.2
Updates on radiatively important atmospheric trace gas concentrations and trends in other parameters from the NOAA ESRL global network
Russell C. Schnell, NOAA/ESRL/GMD, Boulder, CO
The NOAA ESRL Global Monitoring Division (GMD) conducts long-term, global scale measurements of atmospheric components that are forcing global climate change or depletion of the Earth's protective ozone layer, as well as solar and terrestrial radiation. Parameters monitored include greenhouse gases, aerosol particles, ozone, ozone-depleting gases, and solar and terrestrial radiation at five manned Baseline Observatories. Additional measurements at 120 other locations are conducted in 34 U.S. States and 67 countries. The observatories at Mauna Loa, Hawaii and at the South Pole, Antarctica have been in continuous operation since 1957. The Mauna Loa carbon dioxide record is considered one of Earth's most important, long-term geophysical records. The other three manned observatories are Point Barrow, Alaska (1974); Trinidad Head, California (2001); and Cape Matatula, American Samoa (1974).
In 2007, the globally averaged carbon dioxide growth rate was 2.23 ppm and in May 2008 the concentration was 386.5 ppm at Mauna Loa Observatory. In 1958, the first full year of CO2 measurements at Mauna Loa, the concentration of CO2 was ~ 315 ppm. Carbon dioxide contributes ~50% of the forcing from anthropogenic contributions of long-lived greenhouse gases. The global burden of methane, responsible for ~ 20% of the forcing from long-lived greenhouse gases, was relatively steady between 1999 and 2006 compared to an annual growth rate of ~13 ppb in the early 1990's. The reason for this relative stabilization remains elusive. During 2007, globally averaged CH4 concentrations increased by ~10 ppb. This increase appears to be coming from greater than normal emissions from wetlands as suggested by CH4 isotopic measurements. The global growth rate of nitrous oxide (N2O), the third most important greenhouse gas, is relatively steady in the 0.6 to 0.8 ppb/yr range with a global average concentration of ~ 320 ppb.
The previously reported “global dimming” in surface solar irradiance observed over more than 2 decades in NOAA and other network data has now slowly changed direction into increasing surface irradiance, termed by some, as “solar brightening”. Total solar irradiance is now returning to levels measured a quarter of a century ago.
Gas, aerosol and solar radiation measurements at Arctic observatories at Barrow, AK; Eureka, Canada; and Summit, Greenland; all operating with similar instruments, show that forest fire smoke can be swept from the interior Alaska across the Arctic basin to Greenland and beyond. This smoke produces an appreciable cooling at the surface, independent of any effects the black carbon fallout may have on decreasing sea ice albedo and thus increased surface heating.
Data from the NOAA stratospheric aerosol lidar network shows an unexplained ~50% increase (~8%/yr) in stratospheric aerosol backscatter between 2000 and 2008 that is independent of volcanic eruptions. This amounts to an optical depth increase of from 0.005 to 0.007 over the past decade.
In the 15 years prior to 2004, steady or declining rates of HCFCs were observed in the global background atmosphere. But, since 2005, the accumulation rates of these gases have increased substantially; the growth rates of HCFC-22, HCFC-142b, and HCFC-141b were 50% to 100% larger in 2007 than measured in 2004. Increased outputs of these gases from developing countries are believed to be the cause. Long-term surface ozone measurements show no persistent global trends over multi-decadal periods.
The sum total of the radiative forcing of all of the long-lived gases is summarized annually by NOAA into the Annual Greenhouse Gas Index (AGGI). The AGGI shows that since 1979, the warming influence of all long-lived greenhouse gases combined has increased 33% and continues to climb at ~1.5% per year.
Joint Session 5, Global environmental observing systems including, but not limited to, the Global Climate Observing System (GCOS), Global Ocean Observing System (GOOS), and Global Terrestrial Observing System (GTOS)—II
Thursday, 15 January 2009, 11:00 AM-12:15 PM, Room 122BC
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