Skip to comments.Tree Rings Show A Period Of WideSpread Warming In The Medieval Age
Posted on 03/26/2002 5:46:53 PM PST by blam
March 26, 2002
Tree Rings Show a Period of Widespread Warming in Medieval Age
By KENNETH CHANG
A new study of old tree rings shows that 1,000 years ago, long before power plants and sport utility vehicles, temperatures across North America, Europe and Asia rose in a period of unusual warmth.
In warm weather, trees thrive and grow a thick ring of wood in their trunks for that year. In cold years, growth slows and the tree ring is thin.
Temperatures were known to be warm in Europe between 900 and 1100, what is known as the Medieval Warm Period. Collecting wood samples in 14 locations that cover a swath of the globe from New Orleans north to the top of Alaska, researchers from Columbia University's Lamont-Doherty Earth Observatory and the Swiss Federal Research Institute found evidence that the warm temperatures extended to much of the Northern Hemisphere.
Writing in the current issue of the journal Science, the scientists say the data demonstrate that temperatures naturally rise and fall over the centuries. The scientists, however, add that their data do not argue against the view that artificial emissions so-called greenhouse gases have set off the global warming of recent decades.
"I never intended or meant to imply that that's the case," said Dr. Edward R. Cook, an author of the Science paper and an expert at Lamont-Doherty on reconstructing climate from tree rings.
Greenhouse gases like carbon dioxide from factories and cars trap heat in the atmosphere. Globally, temperatures have risen about 1 degree Fahrenheit over the last century.
Although the climate has repeatedly swung between warm and cold over the Earth's 4.5-billion-year history, the usual interpretation is that the climate has been quite stable since the end of the last ice age 10,000 years ago.
"This record suggests that the amplitude of natural variability is larger than the other records have suggested in the past," Dr. Cook said.
The data may help scientists refine their climate models to provide better predictions of future warming.
An earlier reconstruction of temperatures over the past millennium by Dr. Michael E. Mann, a professor of environmental sciences at the University of Virginia, found a much smaller temperature rise in the Medieval Warm Period, but the different numbers do not necessarily contradict each other.
Dr. Mann's data covered the entire Northern Hemisphere in addition to tree rings, he included other indicators of past temperature like coral reefs and ice cores from Greenland. Temperatures in the tropics vary much less than those in the higher latitudes, he said.
Because the authors of the Science paper averaged their data over 40 years to smooth out year-to-year fluctuations, their temperature curve does not reflect the most recent warming.
"They've kind of smoothed out of the record," Dr. Mann said. "It doesn't support the conclusion that the medieval warmth was comparable to the latter 20th century warmth."
Rather, the peak temperatures in the Medieval Warm Period are similar to those seen in the first half of the 20th century, and that warming, most scientists agree, was induced naturally, by a brightening of the sun.
Oh, sorry, it said "tree rings". My bad.
The article points out what I have stated in earlier posts: that ambient atmospheric temperatures and ambient ocean temperatures don't always "track" over time. With tree rings, the relationship with "warmth" is pretty well established, but cloud cover, brightness of the sun light (an effect of upper atmospheric scattering), etc., are also factors in ring development.
The article also points out the MYTH that ambient temperatures have been consistent until recently. Consider that natural processes such as volcanic activity can affect world-wide temperatures by 2-3 degrees F, the so-called global warming process is still a theory without a solid scientific basis in fact!
Doesn't it coincide with the decline of the Mayan in Mexico and the Anaszasi(sp) in the American SW?
Note: this topic is from . Thanks blam.
Note: this topic is from . Thanks blam.
Researching a climatic catastrophe that rocked the Earth in A.D. 535, causing two years of darkness, famine, drought and disease.
Written records from China, Italy, Palestine [sic] and many other countries suggest a huge catastrophe blighted the world in 535AD. But the cause of it has been uncertain.
Was it a comet? An asteroid? A volcano? Archaeologist David Keys reveals the latter is to blame for the Dark Ages of famine and plague that shaped the world order of today.
Content licensed from Digital Rights Group (DRG).
Produced by 3BM Television Limited.
Catastrophe - The Day the Sun Went Out - Part 1 of 2 (Mysteries Of History Documentary) | Timeline - World History Documentaries | Published on June 23, 2017
Catastrophe - How the World Changed - Part 2 of 2 (Mysteries Of History Documentary) | Timeline - World History Documentaries | Published on June 24, 2017
The event in the Indonesian “Book of Kings”, that reportedly split Java from Sumatra — in historical times — is precisely dated, to “the year 338 Saka (416 AD)”, IOW, more than a century earlier than Key’s claiming. The British bias against large impacts is on full display in the documentary — but it’s still interesting and well worth watching.
NYT link says page not found.
Perhaps, but then again, the topic is from 2002.
[snip] The Avars were a confederation of heterogeneous (diverse or varied) people consisting of Rouran, Hephthalites, and Turkic-Oghuric races who migrated to the region of the Pontic Grass Steppe (an area corresponding to modern-day Ukraine, Russia, Kazakhstan) from Central Asia after the fall of the Asiatic Rouran Empire... [/snip]
I always wanted to make a sequence of events related to Krakatoa since 1883 eruption. I just needed to find, organize and edit parts of footages, clips, documentaries and photos in a "time line".
Special Thanks to all You Tube fellows for sharing their amazing material.Their names are mentioned on the epilogue.This video has educational purposes only.
Krakatoa - Chronology - 416AD to 2019 | Marco Cianflone | Published on April 7, 2019 | Suggested by PioneerProductionsUK | Song: Crossroads Limiter | Artist: Charles Faravel | Album: Oxygene
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