Geoscience Reference
In-Depth Information
simply deny that climate change was happening at all, especially those who were profiting handily
from civilization's addiction to fossil fuels.
Some leading climate scientists such as NASA's James Hansen have argued that CO
2
not only
needs to be stabilized below 450 ppm, but in fact must be brought back to a level even lower than
present. Based on geological evidence regarding ice amounts and sea levels that prevailed in past
warm climates, Hansen argues that we need to bring CO
2
down to levels lower than those that
persisted when I first entered into climate research in the early 1990s—to 350 ppm, to be specific.
6
In the December 2009 climate change negotiations in Copenhagen, Denmark, a consortium of low-
lying island nations already threatened by rising sea levels lobbied for such a target.
7
This target has
even been incorporated into the name of the grassroots climate change campaign founded a few years
from current levels would require not only dramatically reducing emissions, but in fact making them
negative—that is, actively taking ambient CO
2
from the air through expensive and, as yet, largely
untested technologies such as open air carbon capture (which attempts to suck the CO
2
out of the air,
mimicking what plants do naturally, but at a greatly accelerated rate and without releasing carbon into
the atmosphere as plant matter does when it dies and decomposes).
Suppose we were instead to continue with business as usual, shunning efforts to curtail carbon
emissions. The impacts on our civilization and environment could be profound. By doing so, we
might well be committing ourselves to the melting of the major ice sheets, resulting in a sea level rise
as much as six feet by the end of this century
8
and, eventually, twenty feet or more, thus ensuring
extensive loss of coastal settlements around the world, including the East and Gulf Coasts of the
United States, and the potential disappearance of many low-lying island nations. Many coastal
regions, including the U.S. East and Gulf Coasts, might feel the double whammy of inundation from
sea level rise and increased erosion and destruction from potentially more powerful hurricanes fueled
by warmer oceans. Increasingly widespread and severe droughts would likely take hold over the
major continents, including North America, as precipitation became increasingly intermittent and
moisture evaporated more readily from warmer soils. Many regions would likely also see increased
flooding from more intense rainfall events.
Among the potential impacts would be greater social conflict resulting from movements of large
numbers of environmental refugees and increased competition for available resources within and
among nations, more widespread famine due to declining agricultural productivity in developing
tropical nations already struggling with hunger and malnutrition, and threats to human health and even
mortality from potential increases in the spread of infectious disease and stress-related deaths from
more frequent and extreme heat waves. Key ecosystems may be lost, including coral reefs and the
summer Arctic sea ice environment critical to the survival of polar bears.
Of course, there could be potential benefits in some cases. Agricultural productivity, for
example, might increase in some midlatitude regions owing to longer growing seasons, as long as
freshwater supply remains available—an important caveat. However, when all the various potential
impacts of the climate changes are taken into account, the weight of impacts have been shown to be
decidedly negative, and increasingly so as warming progresses.
9
It is possible that the models that
indicate a temperature rise of only 3 °F or so for CO
2
doubling are right, that the changes will be
modest enough that we, and many other living things, might be able to adapt. That appears unlikely,
