Many of these observations correlated with global climate change are projected continue into the next century. In fact, the Intergovernmental Panel on Climate Change, the world’s authority on climate change, predicts that the 21st Century will see a warming much more drastic than that seen during the 20th Century. Global mean temperatures are projected to increase (depending on various scenarios) by a range of 1.4°C to 5.8°C, with a corresponding rise in sea levels of 9 millimeters to 880 millimeters. This would place an even greater stress on global ecosystems, displacing many species, causing desertification in lower latitudes and perhaps increasing agricultural production in higher latitudes. (IPCC, 2002)

This brings about a question of even greater importance: How much of the increase in global temperature from 1860 to 2000 is due to anthropogenic causes, and how much is due to natural causes? The Causes of 20th Century Warming seeks to answer this question. Essentially, Zwiers and Weaver come to the conclusion that anthropogenic causes, moderated by natural climate fluctuations and natural forcing have produced climate change as observed in the 20th Century.

It is essential, therefore, that if we are to attempt to slow this current trend of global warming, and avoid the consequences that a warmer earth would bring about, research of this nature needs to be ongoing. Even though there never will be absolute certainty in predicting future climate change, increasing scientific accuracy will be crucial if international climate change mitigation is going to take place.

But why is the earth warming at such a greatly accelerated rate, not seen in the past 10,000 years? This question becomes hugely important when modeling future climate changes. Much of the recent focus has been on anthropogenic causes of climate change, including the release of so-called greenhouse gasses, land use changes, and the increased use of livestock for human protein intake. However, many fluctuations in global climate prior to the industrial revolution cannot be attributed to anthropogenic causes. Therefore, there must be underlying natural factors contributing to climate change.

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