Geoscience Reference
In-Depth Information
cur in complex systems. This is true of banks, frozen ponds, and global
climate processes. Current research indicates that a number of sectors
and earth systems may be threatened in the next century or so once the
earth has warmed by 3°C or more.
You might be wondering whether I am making a mountain out of a
bump in the road. Climate change is part of earth's history, from the
warm periods of the dinosaurs to the cold periods when New England
lay under a mountain of ice. Is this time really different?
It is true that large changes in climate have occurred in the past,
some of them extremely rapidly. During a period known as the Younger
Dryas, about 12,000 years ago, the earth apparently experienced one-
third of an ice age in a few decades. In other words, one-third of the dras-
tic cooling that buried much of North America under a giant ice sheet
happened in a few decades of abrupt climate change. Similar abrupt
climate changes occurred in earlier periods, although the reasons are
not well understood.
But this time is different because of the pace of human-induced
climate change over the next century and beyond. Climatologists
have concluded that no climate changes of the speed and scope we
are currently witnessing have occurred through the course of human
civilization (roughly the last 5,000 years). While there are no reliable
instrumental temperature records much before the twentieth century,
proxy records can be gathered from sources such as ice cores, tree rings,
ancient plant pollens, and boreholes in the ground. The best guess is
that the rate of global climate change people will face over the next
century will be about ten times as rapid as any change experienced by
humanity during the last fi ve millennia. So while perhaps not unpre-
cedented on the scale of geological time, it is unprecedented during the
era of human civilization.
This concludes the introduction to the broad concepts of climate
change. We have seen how global warming has its wellspring in eco-
nomic growth and technologies—particularly in the harnessing of fos-
sil fuels to power our societies. Further, we observe how largely invisible
greenhouse gases such as CO
2
are changing the energy balance of the
