CRITICAL ISSUES FOR LONG-TERM CLIMATE MONITORING

Even after extensive re-working of past data, in many instances we are incapable of resolving important aspects concerning climate change an d variability. Virtually every monitoring system and data set requires better data quality, continuity, and homogeneity* if we expect to co nclusively answer questions of interest to both scientists and policy- makers. This is a result of the fact that long-term meteorological dat a, (both satellite and conventional) both now and in the past, are and have been collected primarily for weather prediction, and only in som e cases, to describe the current climate. Long-term climate monitoring , capable of resolving decade-to-century scale changes in climate, req uires different strategies of operation. Furthermore, the continued de gradation of conventional surface-based observing systems in many coun tries (both developed and developing) is an ominous sign with respect to sustaining present capabilities into the future. Satellite-based ob serving platforms alone will not, and cannot, provide all the necessar y measurements. Moreover, it is clear that for satellite measurements to be useful in long-term climate monitoring much wiser implementation and monitoring practices must be undertaken to avoid problems of data inhomogeneity that currently plague space-based measurements. Continu ed investment in data analyses to minimize time-varying biases and oth er data quality problems from historical data are essential if we are to adequately understand climate change, but they will never replace f oresight with respect to ongoing and planned observing systems require d for climate monitoring. Fortunately, serious planning for a Global C limate Observing System (GCOS) is now underway that provides an opport unity to rectify the current crisis.