Mega-cities cause 'islands of heat' around the world

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http://www.telegraph.co.uk:80/et?ac=000154642417163&rtmo=02K0serq&atmo=rrrrrrbq&pg=/et/00/2/23/wass23.html

Mega-cities cause 'islands of heat' around the world By Roger Highfield, Science Editor

A SATELLITE study has shown how the spread of mega-cities around the world can create vast "heat islands" that boost smog, trigger thunderstorms and reduce the productivity of the land.

Urbanisation and industrialisation have resulted in the growth of city sprawl that can increase temperatures by up to 12F relative to the surroundings. This is happening all over the world. In China's Pearl River delta the urban sprawl has grown by 319 per cent between 1988 and 1996.

Dr Dale Quattrochi, of Nasa, told the American Association for the Advancement of Science about a study of Atlanta, nicknamed "Hot-Lanta" and subject to phenomenal growth, losing 55 acres of trees every day for two decades. Now the city is so thick with asphalt and air conditioners that it is a heat island that soaks up radiant energy during the day and holds on to it at night.

As a result, it needs more energy for air conditioning and there is more ozone, the major component of smog, as the mercury rises. Mega-cities even create their own weather. As Atlanta holds on to heat at night it creates a low pressure system, with hot air rising and cooler surrounding air rushing in to replace it. That cooler air condenses and forms thunderclouds, boosting the number of storms.

Dr Quattrochi described how heat islands could be cooled with various measures, from energy efficiency to planting trees and installing reflective materials on roofs to stop buildings heating up so much in summer.

Dr Marc Imhoff, of Nasa Goddard Space Flight Centre in Greenbelt, Maryland, said he had used satellite data to study the effect of urbanisation on photosynthetic production - harnessing of sunlight by plants. Night-time images from a satellite were used to determine which areas and how much land have been converted to urban, suburban or industrial use.

Annual photosynthetic productivity can be reduced by up to 20 days in areas where housing and commercial land use is dense, even though the heat island effect boosts the growing season. He said: "This could have implications in climate change, especially in the Northern Hemisphere."

-- Old Git (anon@spamproblems.com), February 22, 2000

Answers

I have sat in my office and watched storms blow up over Atlanta and drift off to the east and south. Pretty clear to me that's what's going on. The tree loss has ended up causing a lot of urban flash flooding and erosion, too. Stupid greedy developers.

-- ThunderBoomer (raindrops@yourhead.wet), February 22, 2000.

Tuesday February 22, 2000 11:35 p.m. EST

Researchers Say Global Warming May Be Speeding Up

WASHINGTON (AP) -- A recent series of record world temperatures may indicate a speedup of global warming, researchers say.

For 16 consecutive months - from May 1997 to September 1998 - each month broke the previous monthly world average temperature record, scientists from the government's National Climatic Data Center noted in a paper that will appear in the March 1 issue of Geophysical Research Letters.

The team, led by Thomas R. Karl, calculated that there is only a one in 20 chance that the string of record high temperatures was simply an unusual event.

More likely, they indicated, it marked a change to faster warming.

``It raises a flag because it was such an unusual event that we need to watch very carefully in the next several years, because, indeed, it could be a signal of an increased rate of temperature increase,'' Karl said in a telephone interview.

Since completing the research, the data for 1999 have been compiled. They found that 1999 was the fifth warmest year on record. It would have been expected to be cooler because of La Nina, a cooling of the waters of the central Pacific Ocean.

Many scientists in recent years have become concerned about global warming, worrying that exhaust gases from factories and automobiles would cause the planet to warm up by trapping heat from the sun, somewhat like a greenhouse. Others, however, note that changes recorded to date remain within the scope of normal variation.

International agreements have been negotiated in an effort to slow the release of carbon dioxide in hopes of preventing a rise in temperatures that some researchers have suggested could begin having an impact within a century or so.

On Tuesday the General Accounting Office, the investigative arm of Congress, released a report implicating jet exhaust from aircraft as a factor in global warming.

Temperatures have increased during this century, although not as fast as feared by some, and long-term comparisons are hard to make with only about a century of instrument-collected temperature data available.

The researchers at the Asheville, N.C., Climate Center, part of the National Oceanic and Atmospheric Administration, analyzed data from land-based and satellite instruments.

They concluded that the rate of warming since 1976 is greater than the average rate over the late 19th and early 20th centuries. To account for the string of record setting temperatures, the average rate of global temperature increase since 1976 would have to be 5 degrees per century, they said.

The United Nations Intergovernmental Panel on Climate Change had projected the rate of warming for the 21st century at 2 degrees to 6 degrees.

Karl and his colleagues reported that over the past 25 years the rate is 4 degrees to 5 degrees per century.

Karl and his colleagues are not ready to say with certainty that the rate of global warming has suddenly increased, however, noting that unusual events do sometimes happen.

-- Old Git (anon@spamproblems.com), February 22, 2000.


The rise in temperature because of larger and larger heatsink cities is how they are trying to convince people that global warming is real.There are three ways to record temperature--1)by using surface stations,usually if not always located in cities,2)by weather balloons,3)by using satellite technolgy.2 and 3 are usually very close to each other.1 on the other hand continues to rise as our cities get larger and larger,and does not corelate with the other two.It is time people started realizing that global warming is a political agenda,not a weather change.

-- just a thought (tigerpm@netscape.com), February 23, 2000.

My personal study of the heat island affect for the Phoenix metro area is that the rising heat forces thunderstorms around the area, so the weather station at Sky Harbor Airport receives less and less moisture from year to year.

-- Guy Daley (guydaley@bwn.net), February 23, 2000.

Guy,I also live in Phoenix,the Bethany-I17 area.Have you noticed that the reported Airport temperatures are 6-8 degrees hotter than the rest of the city?I attribute this to the tarmac runways,which are 8ft thick concrete based.This makes one excellent heat sink to keep the overnight temps from getting down to normal.Remember the global warming people predicting that the night time lows would be higher?

-- just a thought (tigerpm@netscape.com), February 23, 2000.


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