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Possibility of Abrupt Climate Change Needs Research and Attention

Global climate, like other complex systems, is subject to abrupt changes if stressed. Global warming could cause such an abrupt shift, which could lead to severe problems for humans and other life.

Date: Dec. 11, 2001
Contacts: Bill Kearney, Media Relations Officer
Andrea Durham, Media Relations Assistant
(202) 334-2138; e-mail < news@nas.edu>

Most climate-change research has focused on gradual changes, such as the processes by which emissions of greenhouse gases lead to warming of the planet. But new evidence shows that periods of gradual change in Earth's past were punctuated by episodes of abrupt change, including temperature changes of about 10 degrees Celsius, or 18 degrees Fahrenheit, in only a decade in some places. Severe floods and droughts also marked periods of abrupt change.

A new report from the National Academies' National Research Council says greenhouse warming and other human alterations of the climate system may increase the possibility of large, abrupt, and unwelcome regional or global climatic events. Researchers do not know enough about such events to accurately predict them, so surprises are inevitable.

If the planet's climate is being forced to change -- as is currently the case -- it increases the number of possible mechanisms that can trigger abrupt events, the report says. And the more rapid the forced change that is taking place, the more likely it is that abrupt events will occur on a time scale that has immediate human and ecological consequences.

There is no need for undue alarm, however, about the possibility of sudden climate change, because societies have learned to adapt to these changes over the course of human history, said the committee that wrote the report. Nevertheless, the committee said research into the causes, patterns, and likelihood of abrupt climate change is the best way to reduce its impact. Overall, research should be aimed at improving modeling and statistical analysis of abrupt changes. An important focus of the research should be on mechanisms that lead to sudden climate changes during warm periods, with an eye to providing realistic estimates of the likelihood of extreme events. Poor countries may need more help preparing for abrupt climate change since they lack scientific and economic resources.

The planet's past climate record also needs to be understood better, according to the report. Scientists have a variety of means to study what the climate was like thousands of years ago. For example, researchers look at tree rings to examine the frequency of droughts and analyze gas bubbles trapped in ice cores to measure past atmospheric conditions. With such techniques, scientists have discovered repeated instances of especially large and abrupt climate changes over the last 100,000 years during the slide into and climb out of the most recent ice age. For instance, the warming at the end of the last ice age triggered an abrupt cooling period, which finished with an especially abrupt warming about 12,000 years ago. Since then, less dramatic -- though still rapid -- climate changes have occurred, affecting precipitation, hurricanes, and the El Niņo events that occasionally disrupt temperatures in the tropical Pacific. Examples of abrupt change in the past century include a rapid warming of the North Atlantic from 1920 to 1930 and the Dust Bowl drought of the 1930s.

Simulating abrupt climate changes using computer models is particularly difficult because most climate models respond in a linear manner in which a doubling of the factor forcing change -- greenhouse gases, for instance -- doubles the response. However, abrupt climate changes show that a small forcing may cause a small change, or may force the climate system across a threshold and trigger huge change. A massive discharge of fresh water from lakes dammed by melting ice sheets, which suddenly changes climate conditions worldwide, is an example of threshold-crossing. Chaotic behavior in the climate also may push it across a threshold without any apparent external forcing.

The collapse of some ancient civilizations has been associated with abrupt climate changes, especially severe droughts, but humans have shown great resilience as well. Fast changes make adaptation more difficult, so research should be pursued to identify strategies that reduce vulnerabilities and increase the adaptability of economic and ecological systems, the committee said. It noted that many proactive policies might provide benefits regardless of whether abrupt climate change occurs. Some steps that deserve careful scrutiny include reducing emissions to slow global warming, improving climate forecasting, slowing biodiversity loss, and improving water, land, and air quality.

The report was sponsored by the U.S. Global Change Research Program, with additional support from the National Bureau of Economic Research Program on International Environmental Economics at Yale University. The National Research Council is the principal operating arm of the National Academy of Sciences and the National Academy of Engineering. It is a private, nonprofit institution that provides science and technology advice under a congressional charter. A committee roster follows.

Read the full text of Abrupt Climate Change: Inevitable Surprises on the Internet at < http://www.nap.edu>. Copies of the report will be available for purchase early next year from the National Academy Press; tel. (202) 334-3313 or 1-800-624-6242. Reporters may obtain a pre-publication copy from the Office of News and Public Information (contacts listed above).

homepage: homepage: http://www.prototista.org/E-Zine/climatechange.htm

"............societies have learned to adapt....." 03.May.2005 11:08


They adapted alright! In the most recent "Mini Ice Age" about 500 years ago they were forced to eat rotting maggot filled dead horses and roots before many thousands died of starvation.

The "surprise" this article talks about is how suprised you will be how many people turn to canniblism. That is what we or most likely our children and grandchildren have to look forward to.

But our government feels it needs more study.

That's a fact! 03.May.2005 12:10

D. Burbeck

The mini ice age lasted less than ten years, but the growing season failed all over Europe and scientists found evidence of severe drought in North America.

They believe now that these events are all closely tied to the Atlantic Conveyor which, if it shuts down, fails to circulate tropical warmth to the upper lattitudes.......and the growing season is sharply reduced.

This idea of abrupt climate change needs no further study at all. What needs study is why people are not marching on Washington DC demanding immediate

Virtual march, virtual solution 03.May.2005 18:47


It's at  http://www.stopglobalwarming.org/. However, it's from the people who are trumpeting the CLIMATE STEWARDSHIP ACT like its the solution to everything and like its emissions cuts are even close to what's needed. Kyoto is not even close either. The Green Party is really our only hope. That or THE PEAK, as bleak as that might be.

false comparisons 03.May.2005 19:36


the study talks about dramatic changes 100,000 and 12,000 years ago
then talks about some ancient civilizations
as if they were cotemporal
however the "ancient civilizations" flourished within the last 4,000 years
well within the modern mild stable period

notice how they pair in the same sentence
"collapse of some ancient civilizations"
"but humans have shown great resilience as well"
glossing over that "collapse" means war and starvation
severely culling the herd

the 1930's dust bowl was not really a big deal climatically
the rains failed
but the dust was due to stripping native prairie ground cover
exposing naked soil under failed cotton monoculture
and banks' profit taking policies

similarly many of those ancient civilizations
were killed by their own economic policies
minor climatic changed merely tripped the trap
of salinified fields

irrigation has a built-in blowback
you can never stop
if one flooding is missed due to drought or war
accumulated salts kill whatever tries to grow

the falsest comparison of all
previous civilizations with few spectacular exceptions
stayed close to their food
both close in physical distance
and close in supportable population

natural selection applies to us too
that means not just being big enough to take our neighbours' food
but also being close enough to neighbours who have food to take

the council is pulling entire bails of wool over our eyes

rediculus post 03.May.2005 22:22

analysis by the dude

Is the climate a factor in local values that control enron/pge assets? Is a mini ice age relavent to your being robbed blind by a oligopoly?

WTF Is this bait an switch? Irrelevancy to a new level!