• The Focus on Atmospheric Aerosols activity was initiated in 1995 as a result of the merging of the International Global Aerosol Program (IGAP) with IGAC. The principle objective was to improve understanding of the role of atmospheric aerosols in climate forcing and in the prediction of changes in global climate and geospheric-biospheric processes.

• GLOCHEM sponsored several campaigns including the Mauna Loa Observatory Photochemistry Experiment (MLOPEX). MLOPEX made concurrent measurements of the key species that play controlling roles in the photochemical transformation of ozone, odd nitrogen, and odd hydrogen species in the remote free troposphere. The results were published in JGR – Atmospheres. GLOCHEM also coordinated the Second Tropospheric Ozone (TROPOZ-II) activity, which measured chemically active gases in the free troposphere.

• The GHOST activity was implemented in 2003. Its premise was built upon the need to understand the chemical importance and distribution of OH in the troposphere as well as explore whether the level OH abundance is due to natural processes versus man made disturbances.

• GIM was formed as a merger project from the International Global Aerosol Program (IGAP) project MEARC in 1997 and was implemented under the IGAC Global Focus. GIM aimed to address the development and application of advanced 3-D global chemical transport and coupled climate and chemistry models, emphasizing tropospheric applications. It conducted a series of model intercomparison exercises focusing on key problems in tropospheric chemistry as well as collaborated with other modeling development efforts.

• GLONET was designed in 1996 to improve the quality of O3 profile measurements, and implant new stations in geographic regions critical for achieving global coverage. Also, through its sub-project International Tropospheric Ozone Years (ITOY), it began the establishment of a global database for validation of chemistry and transport models. The focus was directed towards expanding ozonesonde stations in tropical and subtropical areas. It conducted inflight intercomparison of ozone-sondes and airborne UV-photometers with the Jülich Ozone Intercomparison Experiment (JOSIE).

The primary objective of the SOLAS/IGAC task HitT is to determine and quantify the importance of reactive halogen compounds (RHCs) in tropospheric chemistry and climate forcing. Key themes are the influence of RHC on the oxidative capacity of the atmosphere, the ozone budget, as well as in aerosol nucleation and growth.

The primary goals of HESS were to estimate the strength of trace gas sources and sinks in high-latitude ecosystems on a global scale, determine the principal ecological and environmental correlations and understand the importance of them on environmental change. HESS conducted the Northern Wetlands Experiment campaign, which looked at the importance of Northern wetlands as sources of biogenic gases contributing to the atmosphere. The activity merged into BATREX in 1999.

Through ITCT, IGAC endorsed a series of research campaigns on intercontinental transport and chemical transformation. These tasks included three campaigns on aerosol characterization experiments (ACE-1, ACE-2, and ACE-Asia); the Polar Study using Aircraft, Remote Sensing, Surface Measurements and Models, of Climate Chemistry, Aerosols, and Transport (POLARCAT); participation in the New England Air Quality Study; and the ITCT-Lagrangian-2k4 experiment that was part of ICARTT.

• The objective of MAGE was to study air-sea exchange and the formation and transformation of marine aerosols in part by making Lagrangian observations. MAGE organized the chemical experiment of The Atlantic Stratocumulus Transition Experiment (ASTEX), which took place in June 1992 in the stratocumulus-capped marine boundary layer. The purpose was to study the factors influencing the formation and dissipation of marine clouds. MAGE also organized an intercomparison experiment, ASGAMAGE, which had two phases, the first in May and the second in October of 1996.

• The Mega-cities: Asia Task Team facilitated better coordination between groups making measurements of aerosols and oxidants in and around large cities in Asia. Their activities included maintaining a centralized web page; holding periodic workshops to increase communication between research groups; organizing instrument intercomparisons; and facilitating collaborative publications.