Those of you who roam the internet looking for information on climate and weather subjects may have come across the web site for the newspaper "USA Today" ( www.usatoday.com ) which has a weather page with its "Ask Jack" Column, where you can send in questions which may be answered online. A large number of past questions and answers can be accessed which all add up to an interesting data base of information on weather related topics.
Looking through this material late last year I noticed that Jack's answers
on most greenhouse & climate change issues were pretty balanced..........
........until I saw the question below under the "Climate Change" heading
relating to the urban heat island of Atlanta GA, a subject which I had
not long ago put up a page on and where NASA had published their Hotlanta
promotion of their GOES satellite infra-red images, see my Atlanta page.
The Question:
This question is about global warming. I know that large cities have a "heat island" effect keeping temperatures in urban area warmer than in the countryside, especially at night. My question is, as the population rises and cities grow, are temperature readings being distorted? How is this corrected when inspecting temperature trends? As an example, the Atlanta airport was in rural countryside in 1957 and in 1997 is surrounded by industrial development, so Atlanta temperature readings today are probably influence by a heat island that did not previously exist.
Now for Jack's Reply:
Those studying climate go to quite a bit of effort to ensure that urban heat island effects do not distort the climate record. The USA is fortunate in having a system of voluntary climate observers all over the country, especially in rural areas. In many cases these records go back more than 100 years. In the case you mention, of Atlanta, climatologists are able to use records from locations around the Atlanta area, which are still rural, to see how the heat island of the growing city has changed airport readings.
If gets even more complicated than this. Over the years the types
of thermometers used have changed, which could affect the readings. Scientists
use records of these and other changes over the years, such as times of
the day that observations are made, to develop a consistent set of readings.
While long-term records for the USA, and some other nations, are generally
good, little data is available for large areas of the world. In recent
years, satellites have been used to take global temperature readings. But
these records go back only to the 1970s and there are problems relating
them to other kinds of temperature records. Our climate change index has
links to several web sites with more information. Under the "Climate data"
headline you'll find links to more on the problems of gathering climate
data as well as links to such data.
(3-24-97)
End of Jack's Reply
Analysis of Jack's Reply with my comments inserted in italics:
Those studying climate go to quite a bit of effort to ensure that urban heat island effects do not distort the climate record. This may be true of some research groups but such work is not quoted by the IPCC as are the Jones / CRU global compilations which your reader would have seen reported in the media.
The USA is fortunate in having a system of voluntary climate observers all over the country, especially in rural areas. In many cases these records go back more than 100 years. In the case you mention, of Atlanta, climatologists are able to use records from locations around the Atlanta area, which are still rural, to see how the heat island of the growing city has changed airport readings. Of course this can be done but the facts are that the CRU / Jones team uses Atlanta uncorrected
If gets even more complicated than this. Over the years the types of
thermometers used have changed, which could affect the readings. Scientists
use records of these and other changes over the years, such as times of
the day that observations are made, to develop a consistent set of readings.
While long-term records for the USA, and some other nations, are generally
good, little data is available for large areas of the world. In recent
years, satellites have been used to take global temperature readings. But
these records go back only to the 1970s and there are problems relating
them to other kinds of temperature records. Our climate change index has
links to several web sites with more information. Under the "Climate data"
headline you'll find links to more on the problems of gathering climate
data as well as links to such data.
In January 2001 I emailed Jack the following text pointing out shortcomings in his reply on Atlanta. I have had no response despite a second email.
Dear Jack,
I was very interested in your reply to the question
from your site pasted below, because in contrast to the vast majority of
your replies which I find balanced, I think you conveyed
a wrong impression here.
Your correspondent starts by saying his question is about global warming and he is talking about land data.
The Norwich based P.D.Jones et al global compilations so well promoted by the IPCC are far and away the most commonly quoted source of global warming "news" likely to be seen by your correspondent.
I am sure in many cases you are right to say, " Those studying climate go to quite a bit of effort to ensure that urban heat island effects do not distort the climate record."
The simple fact is that Jones in all his versions and updates uses Atlanta uncorrected.
As he uses hundreds of other heat island affected city records.
It is unfortunate that misleading statements appeared in mid-1980's Jones et al peer reviewed papers, for example, ….."very few stations in our final data set come from large cities." In the Jones et al southern hemisphere data, over half of stations extending back through 1900 are from large cities.
Station details are not given in those mid 1980's Jones et al peer reviewed papers; you have to go to the phone book sized publications put out by your DoE Department CDIAC to see exactly which stations are used. How many people can take that time and trouble ?
I would like to thank you for posting so many very informative and interesting replies to such a wide range of your readers questions on climate change subjects where positions can become polarised.
In this one case I hope you can revisit the issue and check on the facts behind your answer. I am sure you will tell me if you think I have it wrong.
Best regards,
Warwick Hughes
Wrap Up:
This is just one example of how the pernicious misinformation put out
by the IPCC and their cohorts over 15 years that has influenced many in
the climatology fraternity.
The IPCC continue to say in their recent Third Annual Report (TAR)
that urban heat islands are "allowed for".
All the CRU / Jones team have ever done in that regard are to;
Corrections such as this which if added every year can cancel out the progressive UHI contamination, are never found in the CRU / Jones data.
Posted 18, July, 2001
You saw it first here.
© Warwick Hughes, 2000
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