In May 1997 a conference on Global Measurement Systems for Atmospheric Com-positionwas organized in Toronto, Ontario, Canada, by three international organizations,the International Global Atmospheric Chemistry Program (IGAC), Stratospheric Pro-cessesand Their Role in Climate (SPARC), and the Global Atmospheric Watch (GAW),collaborating with two local sponsors, the Canadian Space Agency (CSA) and theAtmospheric Environment Service (AES). Additional travel support was provided bythe Natural Environment Research Council (NERC) of the United Kingdom, the Com-mitteeon Space Research (COSPAR), the European Space Agency (ESA), and theWorld Meteorological Organization (WMO). The local arrangements were provided bythe Department of Physics of the University of Toronto.
The conference was organized because of the realization that the chemical compositionof the atmosphere is changing on a global scale and that this has far-reaching implicationsfor the health of the environment and the future of human society. This leads to arequirement that many nations participate in assessing the current state and trends ofthe chemical state of the atmosphere and in turn the assembly of global measurementsystems for atmospheric composition. Finally, the skills of a large number of people invarious professions are required to make such large undertakings politically and sci-entificallyacceptable, as well as financially viable.
Thus this conference brought together about 120 managers, scientists, and policymakers to discuss current knowledge of and predictive capabilities for atmosphericcomposition, to define the near-term requirements for global measurement systems, andto begin developing a framework for more comprehensive systems in the future. A totalof over 120 papers was presented over three days in 15 sessions.
One of the clear messages of the conference was the understanding that no singlemeasurement or modeling effort was sufficient to comprehend the problem, but in allcases a synergy between methods was required to make significant progress on thescience. Increased interaction between the various groups is therefore indicated as thebest way to proceed.
Some of the papers presented at this conference have been gathered here in thisspecial issue of Journal of the Atmospheric Sciences. The diversity of the topics coveredillustrates some of the problems of the field–there are an enormous number of variablesand an enormous diversity in time and space scales. Problems and issues occur on local,regional, and global scales. Some occur quickly and disappear quickly. Some only appearover long periods of time, sometimes longer than human lifetime and certainly longerthan the funding cycles of any agencies. A comprehensive picture will take an extremelylong time to develop, if that goal is even feasible.
The first group of papers concern satellite measurements. Some new instruments arepresented that will be launched within the next few years yielding new information onthe state of the atmosphere. A particular emphasis of these instruments is on the loweratmosphere and the troposhere. The second group of papers concerns aerosols, an at-mosphericcomponent that is extremely pervasive, very important in climate and com-positionstudies, and extremely hard to quantify. The final group concerns measurementsof atmospheric gases with emphasis on the tropospheric region No collection of papersis complete; indeed, if it were possible to produce a complete collection, then our taskwould be done. However, these papers span the gamut of the regime from global mea-surementsfrom space to local measurements from the ground.
The organizers of the conference would like to thank all those who participated inthe conference for their time and efforts, all our sponsors for their generous assistance,and the staff of the Journal of the Atmospheric Science for their assistance in preparingthis special issue.