Clearly, we need some answers if we are to understand our planet's physical and biological phenomena and how they interact, and to determine human contributions to global change phenomena. We need this information so that we may make decisions about our activities in an effort to reduce any detrimental changes we may be making, or to adapt to circumstances we cannot change. Data must be obtained to allow us to understand the basic forces and rhythms of our planetary system, and to distinguish global changes due to "natural" effects from those that have their origins in human activities. This, in turn, requires acquisition of data addressing virtually every aspect of the Earth system over a long enough period that contributions to change by long-term phenomena (e.g., an 11-year Solar cycle) and trends may be circumscribed. These data will be used to generate information that helps planners and policy-makers as they work to ensure a sustainable environment for all of us.

In keeping with the Huttonian Doctrine ("the present is the key to the past" (and probably to the future, as well [writers' addition]), many of the processes have operated continuously at time scales ranging from minutes to vast millenia; most of these also are likely to perform at different spatial scales, ranging from local to subcontinental or over vast oceans, and, for the atmospheric system, at a global horizon. This is synopsized in this generalized space-time diagram:

This diagram suggests that some processes must be studied over relatively small regions and short time frames, whereas others would require worldwide monitoring over extended periods (often beyond the life span of the individual). Nevertheless, even for the latter, useful information can be gleaned from determining the magnitude and frequencies of changes that occur periodically within the processes as they proceed through time and shift in space. Changes affecting large segments of--or even the entire--planet will likely have profound effects within the global system.

Some indication of the intricately convolved components and areas (topics) of import to any of the systems--singly or combined--as they persistently modify the processes acting within them can be grasped from the several (among many) flow diagrams shown below, with minimal comment:

This deceptively simple diagram is similar to those found in nearly all textbooks on environmental science, physical geology, and meteorology. It shows the "fate" of water leaving and returning to the Earth's surface. The process is cyclic in that, eventually, a water molecule leaving the ocean to enter the atmosphere will ultimately return to that source. The rates of movement and the quantities involved (often shown in more detailed diagrams) will vary among the specific processes (and within a process this variation changes in place and time of year). But, in the long run, the cycle comes full circle such that the various amounts involved maintain an overall mass balance, neglecting losses to outer space and influx from meteorites.

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