Global Warming
Global Warming,
Ice Core and Tree Ring Data. See The Happening
We're in a bit of trouble, read what Garry Braasch has to say...
©1999-2005 GARY BRAASCH
Paleoclimate
What caused the ice ages? How long have the tropics been tropical? What drove the Anasazi out of their cliff dwellings and into oblivion? To answer questions like this, scientists are curious about the past climate of the earth. Today, the speed at which greenhouse gases and temperature are changing has given urgency to studies of the past or paleoclimate. We not only want to see into previous eras, but also to have a basis to predict what is to come.
Before about the middle of the 19th Century, when thermometers became common scientific instruments, there are no direct records of the air or ocean temperature. Even today many locations on the planet are not regularly checked to see how warm, cold, dry or wet they are. So geophysicists have searched for ways to infer temperature and moisture levels by the effects they have had on bodies of water, glaciers and living things. There is intense study of ancient lake bottom mud (containing yearly layers of silt and pollen, etc), deep ocean sediments laid down tens of thousands of years ago (with the remains of tiny sea creatures affected by ocean conditions), glacier and ice cap cores (the oldest of which recovered ice deposited half a million years ago), yearly growth rings of trees and corals, and of course fossils of creatures who lived in different past climates.
Results of these investigations have given us understanding of the close relationship between atmospheric carbon dioxide levels and air temperature (Antarctic ice core records), the last thousand years of temperature (tree rings, lake sediments, etc.), and the reality of very rapid changes in temperature (the Greenland ice cap cores), to name some well known results. World View of Global Warming has documented some of this kind of research, beginning with ocean coring near disintegrating ice shelves in Antarctica
This graph shows the measured record of temperature readings back through the mid 19th century, when thermometers were first in widespread use.
There is a tight correlation between the amount of CO2 and methane in the atmosphere and the average world air temperature. More carbon dioxide = higher temperature. Scientists investigating ancient rocks and ocean sediment can see the relationship going back millions of years. None of the correlations is as tight as that extracted from the deep ice core drilled into the Antarctic ice cap at the Russian Vostok base.
Measuring CO2 trapped in the ice and using oxygen isotopes as an indicator of temperatures, J. R. Petit and his co-workers were able to draw this double chart of 420,000 years. None of the CO2 levels they found is as high as we have today: "Present-day atmospheric burdens of these two important greenhouse gases seem to have been unprecedented during the past 420,000 years," they wrote in Nature.
Other studies suggest that today's 370 parts per million of CO2 is the greatest in 20 million years -- and it is still going up.
Estimates of more recent past temperatures are based largely on tree rings -- the mark of yearly growth of a tree that is extremely sensitive to local conditions and which over the years etches a chart of climate. Dr. Malcom Hughes of the University of Arizona dendrochronology lab is among a small group of scientists who have cored trees and made cross sections of dead stumps all over the world.
One tree that has been extremely important in reading deep into history is the bristlecone pine of the White Mountains, California, where Dr. Hughes and associates worked in 2002 to extract ring data from thousands of years old wood from pines that died many hundreds of years ago. The dry climate at nearly 12,000 feet preserves these old stumps and their record of climate going back 10,000 years.
Other living things that react to environmental changes also can be read for clues to ancient temperature and growth conditions. Among the most commonly used are coral cores, which are similar to tree rings, and studied here by Kevin Helmle of the National Coral Reef Institute at Nova Southeast University, Dania Beach, Florida.
Each year sediment falls to the bottom of oceans and lakes, and this record can be extracted by inserting hollow tubes into the mud (See Antarctic Section, also).
Sediment cores from both oceans surrounding North America have been studied by scientists like Lloyd Keigwin at Woods Hole Oceanographic Institute to make a picture of geologically recent climate events like the Little Ice Age.
The oldest climate records come from glaciers and ice caps, for which cores extend back almost half a million years (in Antarctica).
Photographs from the World View of Global Warming are available for license to publications needing science photography, environmental groups and agencies, and other uses. Stock photography and assignments available.
Garry's Website
Gary Braasch, Photographer PO Box 400 Nehalem, Oregon 97131 USA Phone: 503.699.6666 Cell: 503.860.1
Home
Yahoo Quick Search
Send E-Mail to: thecosyslughutt@webspawner.comCopyright © 2007 GARY BRAASCH . All Rights Reserved