Rasta TimesCHAT ROOMArticles/ArchiveRaceAndHistory RootsWomen Trinicenter
Africa Speaks.com Africa Speaks HomepageAfrica Speaks.comAfrica Speaks.comAfrica Speaks.com
InteractiveLeslie VibesAyanna RootsRas TyehimbaTriniView.comGeneral Forums
*
Home
Help
Login
Register
Welcome, Guest. Please login or register.
March 29, 2024, 07:31:42 AM

Login with username, password and session length
Search:     Advanced search
25910 Posts in 9966 Topics by 982 Members Latest Member: - Ferguson Most online today: 99 (July 03, 2005, 06:25:30 PM)
+  Africa Speaks Reasoning Forum
|-+  SCIENCE, SOCIOLOGY, RELIGION
| |-+  Science and Technology (Moderators: Tyehimba, leslie)
| | |-+  Scientist Links Man to Climate Over the Ages
« previous next »
Pages: [1] Print
Author Topic: Scientist Links Man to Climate Over the Ages  (Read 7764 times)
Ayinde
Ayinde
*
Posts: 1531


WWW
« on: December 11, 2003, 10:16:13 AM »

By KENNETH CHANG, NY TIMES
Published: December 10, 2003


SAN FRANCISCO, Dec. 9 — Humans have altered the world's climate by generating heat-trapping gases since almost the beginning of civilization and even prevented the start of an ice age several thousand years ago, a scientist said on Tuesday.

Most scientists attribute a rise in global temperatures over the past century in part to emissions of carbon dioxide by human activities like driving cars and operating factories.

Dr. William Ruddiman, an emeritus professor at the University of Virginia, said at a meeting of the American Geophysical Union here that humans' effect on climate went back nearly 10,000 years to when people gave up hunting and gathering and began farming.

Dr. Ruddiman is also reporting his findings in the journal Climatic Change.

In a commentary accompanying the article, Dr. Thomas J. Crowley of Duke University, said he was first taken aback by Dr. Ruddiman's premise. "But when I started reading," Dr. Crowley wrote, "I could not help but wonder whether he just might be on to something."

The climate of the last 10,000 years has been unusually stable, allowing civilization to flourish. But that is only because people chopped down swathes of forest in Europe, China and India for croplands and pastures, Dr. Ruddiman said. Carbon dioxide released by the destruction of the forests, plus methane, another heat-trapping gas, produced by irrigated rice fields in Southeast Asia, trapped enough heat to offset an expected natural cooling, he said.

"The stability is an accident," Dr. Ruddiman said.

Levels of carbon dioxide and methane rise and fall in natural cycles lasting thousands of years, and both reached a peak at the end of the last ice age 11,000 years ago. Both then declined as expected.

Both should have continued declining through the present day, leading to lower temperatures, and a new ice age should have begun 4,000 to 5,000 years ago, Dr. Ruddiman said. Instead, levels of carbon dioxide reversed 8,000 years ago and starting rising again. The decline in methane levels reversed 5,000 years ago, coinciding with the advent of irrigation rice farming.

Copyright 2003 The New York Times Company

Human influence on climate is hotly debated
http://news.bbc.co.uk/1/hi/sci/tech/3307891.stm
Logged
Pages: [1] Print 
« previous next »
Jump to:  

Powered by MySQL Powered by PHP Powered by SMF 1.1.21 | SMF © 2015, Simple Machines
Copyright © 2001-2005 AfricaSpeaks.com and RastafariSpeaks.com
Valid XHTML 1.0! Valid CSS!