Geoscience Reference
In-Depth Information
Summary
Until a few decades ago, it was generally thought that significant large-scale global and re-
gional climate changes occurred gradually over many centuries or millennia, hence the cli-
mate shifts were assumed to be scarcely perceptible during a human lifetime. We now
know that human-induced climate change will radically affect the planet over the next 100
years. In addition, there may be potential surprises in the global climate system, exacerbat-
ing future climate change. As discussed above, these include the possibility that Greenland
and/or the Antarctic could start to irreversibly melt, raising sea level by many metres in the
next century. The North Atlantic driven deep-ocean circulation could change, producing
extreme seasonal weather in Europe. The Amazon rainforest could start to die back due to
the combined effects of deforestation and climate change, causing the loss of huge amounts
of biodiversity. Finally, there is the threat of additional methane being released from gas
hydrates beneath the oceans and permafrost, which could accelerate climate change.
So, what effects could climate change have on human society? We know that abrupt past
climate changes had profound effects on human history. For example, a short, cold, arid
period about 4,200 years ago caused the collapse of classical civilizations around the
world, including the Old Kingdom in Egypt; the Akkadian Empire in Mesopotamia; the
Early Bronze Age societies of Anatolia, Greece, and Israel; the Indus Valley civilization in
India; the Hilmand civilization in Afghanistan; and the Hongshan culture of China. It has
also been shown that climate deterioration, particularly a succession of severe droughts in
Central America during the Medieval Cold Period, prompted the collapse of the classic
period of the Mayan civilization. Moreover, the rise and fall of the Incas can be linked to
alternating wet and dry periods, which favoured the coastal and highland cultures of
Ecuador and Peru.
We know, however, that humans can survive a whole range of climates. The collapse of
these urban civilizations was not simply about climate shifts making an area inhospitable,
rather, it was that those societies were unable to adapt to the climate changes, particularly
the changes in water resources. For example, for the Mayan civilization to have survived, it
would have needed to recognize its vulnerability to long-term water shortages and to have
developed a more flexible approach, such as finding new water sources, developing new
means of conserving water, and prioritizing water use in times of shortage. Hence the next
two chapters are concerned with the global human response to climate change and a discus-
sion of potential solutions, including how to ensure our civilization becomes flexible
enough to deal with the possibility of climate surprises.
