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3.0 Anticipating and Adapting to Climate Change

There is a growing scientific concern that we are already embarked upon a path of climate change of unprecedented magnitude that will occur within our lifetimes—a climate change caused largely by ourselves.

3.1 Expected Climate Change in the Next Few Decades

It is highly probable that a global warming of unprecedented magnitude is now in store, following inexorably the irreversible changes we have made in the chemistry of the atmosphere through fossil fuel burning, CFC use, and land-use practices throughout the world. What is uncertain is when this human-induced warming trend will loom above the natural variability that has always characterized climate. It may be already with us: the average surface temperature of the earth has been slowly, though irregularly, rising for at least the last 100 years. As a result the planet is now warmer than it has been in all years since quantitative temperature records began. We also know that during the past 100 years the amounts of carbon dioxide, methane, and other greenhouse gases in the atmosphere have been climbing at an ever-increasing rate, lending credence to the conclusion that human-induced changes are already evident. The several currently oversimplified computer-based climate models, owing to their different assumptions (mainly regarding the ocean), predict different magnitudes and regional distributions of global warming. They all agree, however, that we must expect a continued climate warming, driven by the long-lived greenhouse gases now resident in the air, and by the increasing amounts of these gases that humanity continues to pour into the atmosphere.

It is highly probable that the world we bequeath to our children and to their children will be climatically unlike any that the earth has experienced in the last 100,000 years. Present evidence indicates that our heirs will experience higher average temperatures and higher sea level; different distributions and intensities of rainfall and droughts; and a different pattern of agriculturally productive regions. The 1988 summer's American drought, whether or not it is related to greenhouse warming, indicates the vulnerability of our agricultural system to relatively minor climate fluctuations, and it is typical of what can be expected in the future.

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