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Global Warming: Consensus vs. Certainty

Climate change involves the systematic change of the global atmosphere, which is inseparably linked to the oceans, the biosphere, and the world's water cycle, including its ice sheets and glaciers. Each of these components is immensely complex, incompletely understood, and linked -- via myriad feedback loops -- to each other. Changes in any one of these components can affect the functioning of any of the other systems. If understanding any part of this complex system weren't hard enough yet, add humans to the mix! Our activities have fundamentally affected not only the atmosphere, but each of the other systems as well.

Scientists are trying to get a handle on the complexity of our environment in various ways. They:

1. track various interactions in the present and study them over long periods in the geologic past;

2. study isolated system components and interactions in controlled experiments in the laboratory;

3. replicate different systems in computer models.

The results of all these studies inevitably lead to two things: the first is a growing understanding of, and greater confidence in, our understanding of the environment and the countless interactions between its parts. As studies using different approaches yield results that confirm and fill in our understanding, scientists feel more confident about their findings. The consensus grows.

The second outcome of this ongoing scientific exploration is an uncovering of all those aspects of the problem that we don't yet fully understand. This is the ultimate paradox of the scientific process: the systematic examination of issues -- without which we'd have all but opinion and suspicion -- results both in more certainty and more uncertainty. Nowhere is this more true than in climate change science.

Given all the unknowns and uncertainties, scientists use different approaches to understand these complex interactions. Generally, the methods scientists use to understand and project future climate, fall into three categories:

1. Use of historical observations and trends -- which help to document changes in climate already underway, and to examine what brought these changes about;

2. Mathematical (computer-based) models -- which use these empirical observations as input to project future climatic conditions under a range of assumptions about emissions, population growth, technological development, environmental interactions, and so on; and

3. What-if scenarios -- which begin by assuming a certain future climate and then examine the range of potential environmental and economic impacts under those conditions.

Each of these methods has contributed different yet important insights to our current understanding of global warming. We have to remember, however, that while we are now seeing the first clear signs of a warming world, the ever-present scientific uncertainty highlighted in the climate change debate is rooted in the necessary focus on the future -- something that by definition cannot be known with certainty. The extremely complex nature of the Earth's climate system as well as that of human society makes predictions about future climate patterns and their impacts especially tricky and open to continued scientific research and debate. But this does not mean that scientists cannot ever know anything with a high degree of confidence or that they are completely divided over global warming.

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