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Climate Change
A scientific look at global climate changes.
Welcome to the Weather Underground's new Climate Change page! We're just getting started, so keep checking back over the next few months for new additions.
About Glaciers
Glaciers exist on all the continents of the world except Australia. Most of the world's glaciers are found near the North and South Poles (for more information about Arctic and Antarctic glaciers, please see our pages on Greenland and Antarctica). A large number of glaciers, however, are found in mid-latitude and tropical regions wherever the right conditions exist.
Glaciers exert a significant influence on a landscape. As glaciers move across the terrain, they pick up rock and debris, carve valleys (see Figure 1), and create landforms. Flowing glaciers erode and scour the ground beneath and to the sides of them. These rivers of ice also pick up boulders, soil, trees, and other debris and carry it along in their flow. Once the glacier begins its retreat, however, this material is deposited wherever the glacier.s ice melts. Kettle lakes are formed when large chunks of ice fall off of retreating glaciers and melt, filling depressions in the ground. For more information on glacial formations, see the links below, which will connect you to some sites with photos and descriptions.
There are two main types of glaciers — valley and continental. Valley or alpine glaciers form in mountainous regions where movement is inhibited by valley walls. Continental glaciers, also known as ice sheets, are "dome-shaped mass[es] of glacier ice… greater than 50,000 square kilometers (12 million acres) (e.g., the Greenland and Antarctic ice sheets)" (NSICD).
Click to read more on our featured issue.
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Latest Monthly Climate Trends |
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Monthly Summary (Updated between the 16th and 19th of each month)
November 2008
The planet continued to stay extremely warm in November, recording its 4th warmest November on record, according to statistics released by the National Climatic Data Center. Fall of 2008 (September, October, and November) was the fifth warmest Fall on record, and the period January-November was the 9th warmest such period. During the most recent 5-year (2004-2008) and 10-year (1999-2008) periods, average global temperatures were the highest on record. Global temperature records extend back 129 years, to 1880. Much of the unusual warmth in 2008 occurred over Asia (Figure 1). The two most notable global weather events of November 2008 were the formation of the Caribbean's Hurricane Paloma (the second strongest November hurricane on record), and the record flooding in southern Brazil on November 22-24. The Brazil floods and associated mudslides, called the worst weather tragedy in southern Brazil history, claimed at least 109 lives.
There is no reason at present to suspect that 2008 represents the start of a global cooling trend. Much of the relative coolness of 2008 can be attributed to the presence of a La Niña event in the Eastern Pacific early in the year, plus the fact we are at a minimum in the sunspot cycle. A significant La Niña event can cause a 0.1 to 0.2°C cooling of global surface temperatures, and a sunspot minima can cool global temperatures by about 0.05°C. It is of interest to note that the coldest year in the past decade (2000) had a similarly sized La Niña event, but was considerably cooler than 2008. Realclimate.org has a more in-depth summary of how 2008's temperatures compare to those in recent decades.
There is neither a La Niña nor El Niño at present--neutral conditions now prevail in the tropical Eastern Pacific. Neutral conditions are expected to persist into February, but many El Niña forecast models are now predicting that a new La Niña event will develop between February and May of 2009.
For the contiguous U.S., November was the 20th warmest November and 41st driest since 1895. For the Fall period of September, October, and November, it was the 32nd warmest.
Sea ice extent
November 2008 Northern Hemisphere sea ice extent was the seventh lowest on record for the month of November, 6% below the mean from 1979-2000, according to the National Snow and Ice Data Center. The record November low was set in 2006.
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Importance of Justification
Featuring Dr. Ricky Rood
Justifying Climate Science: In May I attended the World Modeling Summit for Climate Prediction at the European Center for Medium-range Weather Forecasts. This summit received some press coverage, most notably in Nature. At this summit were a number of themes that have been around for years, notably, big computers, extremely high-resolution models, the relationship between weather and climate, and frustration.In the 1990’s I worked for NASA, and there were these c...
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Unexpected ocean cooling result found to be an error
Featuring Dr. Jeff Masters
Since the publication in 2006 of the paper, Recent cooling of the upper ocean, climate scientists have been scratching their heads, trying to figure out why the upper layer of the ocean had cooled from 2004-2006. Since the oceans absorb more than 80% of the heat from global warming, we should expect to see the oceans heating up if the globe is warming. Climate skeptics pointed to the result as evidence that the planet was not warming after all, although surface and satellite measurements showed that the year 2005 was the warmest or second warmest year on record for the surface of the globe.
Now, the explanation for this apparent cooling of the oceans has been resolved--key measurements made by submersible robot buoys and that indicated the ocean was cooling were found to be in error.
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The Iconic Image Gallery is a collection of figures that show important climactic trends. Click on each for a full-sized version of the image, the message that it contains, and a discussion of what makes it 'iconic'. Keep checking back -- we'll be posting additional images soon!
The Cryosphere: Snow and Ice
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Other Topics:
Coming soon:
- Geoengineering
- Global Dimming
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Copyright © 2009 Weather Underground, Inc.
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Copyright © 2009 Weather Underground, Inc.
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