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If you choose to follow any links to the abstract and/or complete text of the item listed below, you will be leaving the Strategian Web site. If you wish to return to this page from the Web page you are sent to, please use the Back option of your browser. Jeffrey M. Masters The Science of Abrupt Climate Change. (... In the debate on climate change, we are used to hearing about climate changes on the scale of hundreds or even thousands of years. But since the early 1990s, a radical shift in the scientific understanding of Earth's climate history has occurred. We now know that that major regional and global climate shifts as recently as 8200 years ago have occurred in just a few decades or even a single year. If an abrupt climate change of similar magnitude happened today, it would have severe consequences for humans and natural ecosystems. Ice cores hold a amazingly detailed record of Earth's climate ... Scientists had known from previous ice core and ocean sediment core data that Earth's climate had fluctuated significantly in the past. But what astonished scientists was the rapidity with which these changes occurred ... Normal climate for Earth is the climate of sudden extreme jumps--like a light switch flicking on and off. Current theories on abrupt climate change focus on sudden shut downs and start-ups of the Gulf Stream ocean current in the North Atlantic as the most likely cause. The Gulf Stream transports a tremendous amount of heat northward, keeping the North Atlantic and much of Europe up to 9°F [5°C] warmer, particularly in the winter. A sudden shut down of the Gulf Stream would have a ripple effect throughout the ocean-atmosphere system, forcing worldwide changes in ocean currents and in the path of the atmospheric jet stream. Studies of North Atlantic Ocean sediments have revealed that the Gulf Stream has shut down many times in the past, and that many of these shut downs coincide with the abrupt climate change events noted in the Greenland ice cores ... if one can pump enough fresh water into the ocean in the key areas on either side of Greenland where the Gulf Stream waters cool and sink, this will lower the ocean's salinity [and therefore its density] enough so that the waters there no longer sink. The Atlantic conveyor belt and Gulf Stream current will then shut down in just a few years, dramatically altering the climate. Scientists admit that it is possible that Earth's climate may suddenly cross the critical threshold needed to trigger abrupt climate change at any time, and that the extra forcing humans apply to the climate system by emitting large amounts of greenhouse gases into the atmosphere makes this possibility far more likely than it would be otherwise ... long term measurements of the strength of the Gulf Stream circulation, particularly in the deep ocean, are virtually non-existent, and it is simply not known if the recent increase in fresh water to the Arctic may be close to triggering a shut down of the Gulf Stream. A shut down of the Gulf Stream would suddenly decrease the amount of heat in the North Atlantic, leading to much colder temperatures in Europe and North America. The historical records shows us that abrupt climate change is not only possible--it is the normal state of affairs. The present warm, stable climate is a rare anomaly. It behooves us to learn as much as we can about the climate system so that we may be able to predict when the next abrupt shift in climate will come. Until we know better when this might happen, it would be wise to stop pouring so much carbon dioxide into the air. Other keywords and phrases -- global warming, greenhouse effect, ice sheet, national academy of sciences -- from the text of the article) The Weather Underground [Web site] (2004): available online. **The complete text of the article is available at http://www.wunderground.com/education/abruptclimate.asp (the Web site of The Weather Underground)** How to find the above journal, magazine, or other publication? See Step 3: Locate of the Information Strategy for details. Questions? Please let me know. |
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