What Environmental Reporting Leaves Out

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21. NOAA begs to differ...

Last edited Thu Oct 11, 2012, 07:07 AM - Edit history (1)

A Paleo Perspective on Abrupt Climate Change

Imagine that over the course of a decade or two, the long, snowy winters of northern New England were replaced by the milder winters of a place like Washington, D.C. Or that a sharp decrease in rainfall turned the short-grass prairie of the western Great Plains into a desert landscape like you would see in Arizona. Changes of this sort would obviously have important impacts on humans, affecting the crops we grow, the availability of water, and our energy usage.

These scenarios are not science fiction. Paleoclimate records indicate that climate changes of this size and speed have occurred at many times in the past. Past human civilizations were sometimes successful in adapting to the climate changes and at other times they were not.

Because they occur relatively rapidly, these sorts of climate change are called abrupt climate change. Our understanding of past abrupt climate changes and their causes is still in its infancy; most of the research on this topic has been completed since the early 1990s. Scientists have made significant progress, however, in identifying and describing various abrupt events of the past and forming hypotheses about their causes. This paleo perspective will describe the evidence for past abrupt climate change and explore some of the possible causes.

Even from the proxy data that exist, one thing is relatively certain: our climate system is not always well-behaved. It can, and often does, change in surprising ways. Positive feedbacks are a key ingredient for this behavior, amplifying a small change or perturbation in the climate system. Paleo records also show that abrupt changes happen during both glacial and interglacial periods, although they may take on different characteristics when large ice sheets exist on Earth. During the Holocene, for example, regional-scale droughts have been very important, while weakening of the meridional overturning circulation had consequences on the hemispheric-to-global scale during the last glacial period.

Learn NOAA's story of abrupt climate change here: The Story

The supporting data is here: The Data

The possibility of abrupt climate change can't be so cavalierly dismissed, unless you're prepared to take on NOAA's science with something more than a blog post.

There may not be any reason to prepare for abrupt climate change, of course, because we don't know what may be in the cards for us in terms of the nature, the severity or the timing. The other thing that makes planning for abrupt change, whether in climate and food production or global finance, a problematic affair is the human factor: the usual thing that causes large non-linear or inflective changes in human behaviour is the occurrence of an external event, not the attempt to avoid it.