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- Permanent Link:
- http://dpanther.fiu.edu/dpService/dpPurlService/purl/FI15050383/00001
Notes
- Abstract:
- Levels of carbon dioxide and other greenhouse gases in Earth’s atmosphere are
exceeding levels recorded in the past millions of years, and thus climate is being forced
beyond the range of the recent geological era. Lacking concerted action by the world’s
nations, it is clear that the future climate will be warmer, sea levels will rise, global rainfall
patterns will change, and ecosystems will be altered.
However, there is still uncertainty about how we will arrive at that future climate state.
Although many projections of future climatic conditions have predicted steadily changing
conditions giving the impression that communities have time to gradually adapt, for
example, by adopting new agricultural practices to maintain productivity in hotter and drier
conditions, or by organizing the relocation of coastal communities as sea level rises, the
scientific community has been paying increasing attention to the possibility that at least
some changes will be abrupt, perhaps crossing a threshold or “tipping point” to change so
quickly that there will be little time to react. This concern is reasonable because such
abrupt changes—which can occur over periods as short as decades, or even years—have
been a natural part of the climate system throughout Earth’s history. The paleoclimate
record—information on past climate gathered from sources such as fossils, sediment cores,
and ice cores—contains ample evidence of abrupt changes in Earth’s ancient past,
including sudden changes in ocean and air circulation, or abrupt extreme extinction events.
One such abrupt change was at the end of the Younger Dryas, a period of cold climatic
conditions and drought in the north that occurred about 12,000 years ago. Following a
millennium-long cold period, the Younger Dryas abruptly terminated in a few decades or
less and is associated with the extinction of 72 percent of the large-bodied mammals in
North America.
Some abrupt climate changes are already underway, including the rapid decline of
Arctic sea ice over the past decade due to warmer polar temperatures. In addition there are
many parts of the climate system that have been thought to be possibly prone to near-future
abrupt change that would trigger significant impacts at the regional and global scale. For
some of these potential changes, current scientific understanding is insufficient to say with
certainty how significant the threat is. In other cases, scientific research has advanced
sufficiently that it is possible to assess the likelihood, for example the probability of a rapid
shutdown of the Atlantic Meridional Overturning Circulation (AMOC) within this century is
now understood to be low.
In addition to abrupt changes within the climate system itself, gradual climate changes
can cross thresholds in both natural systems and human systems. For example, as air and
water temperatures rise, some species, such as the mountain pika or some ocean corals,
will no longer be able to survive in their current habitats and will be forced to relocate or
rapidly adapt. Those populations that cannot do so quickly enough will be in danger of
extinction. In addition, human infrastructure is built with certain expectations of useful life
expectancy, but even gradual climate changes may trigger abrupt thresholds in their utility,
such as rising sea levels surpassing sea walls or thawing permafrost destabilizing pipelines,
buildings, and roads.
Climate is not the only stressor on the Earth system—other factors, including resource
depletion and ever-growing human consumption and population, are exerting enormous
pressure on nature’s and society’s resilience to sudden changes. Understanding the potential risks posed by both abrupt climate changes and the abrupt impacts resulting from
gradual climate change is a crucial piece in advancing the ability of society to cope with
changes in the Earth system. Better scientific understanding and improved ability to
simulate the abrupt impacts of climate change would help researchers and policymakers
with a comprehensive risk assessment. This report, sponsored by the U.S. intelligence
community, the National Oceanic and Atmospheric Administration, the National Science
Foundation, and the National Academies, examines current knowledge about the
likelihood and timing of potential abrupt changes, discusses the need for developing an
abrupt change early warning system to help anticipate major changes before they occur,
and identifies the gaps in the scientific understanding and monitoring capabilities (the full
Statement of task can be found in Chapter 1).
Record Information
- Source Institution:
- Florida International University
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- Please contact the owning institution for licensing and permissions. It is the user's responsibility to ensure use does not violate any third party rights.
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