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It’s been a disappointing summer for global warming alarmists.

Hollywood, Mother Nature and the media just haven’t cooperated. Even with the unusual situation of two successive hurricanes pounding Florida and another bearing down imminently, global warming hysteria seems to be on ice for now.

Not who but what

UHIE is the acronym for Urban Heat Island Effect.

So what is it?

Very simply, UHIE is the result of buildings and pavement absorbing greater amounts of broad spectrum solar radiation than vegetation does. This makes a difference because the atmosphere does not absorb solar radiation across the spectrum but greenhouse gasses (GHGs such as water vapor, carbon dioxide, methane…) absorb infrared. As buildings and pavement re-radiate absorbed broad spectrum radiation in the infrared band absorbable by GHGs we get an increase in the solar energy available to warm the air in cities and towns. With perpendicular walls increasing collector area, acting as trombe walls (storing and re-radiating energy at night) and excluding cooling breezes and with blacktop paved areas reducing surface albedo (reflection), cities and towns have become highly effective accumulators of solar warmth.

Doesn’t this prove global warming is true?

In a word – no. All it does is remind us of something we’ve known and observed for ages – partially enclosed spaces warm up more in the sun than similar open spaces do.

How significant is UHIE?

It can be very significant. For example, here’s a NASA item on “Hotlanta” stating that urban Atlanta can reach 5 to 8 degrees Fahrenheit (~2.8 to 4.4C) or higher than surrounding rural areas. It’s been quite topical too, “HOT-LANTA EFFECT – Urban heat: Growing season, hardiness affected” – “Heat from cities is lengthening the growing season and allowing for more warm-weather plants” (The Atlanta Journal-Constitution) – see Urban Heat Islands Make Cities Greener (NASA GSFC release).

The above release suggests that UHIE exerts an influence over an area almost 2.5 times the size of the city and we surmise it’s likely to be similar for towns and villages too. This suggests that (being generous) up to 10% of the Earth’s non-ice land surface may be affected to some extent – perhaps 3% of the total globe surface. Because the atmospheric column is not uniformly affected, merely the near-surface portion over the city and tapering off on the downwind “plume,” significantly less than 3% of the troposphere will exhibit UHIE.

To what extent this effect is mitigated by increased albedo from croplands where more absorptive forest and scrub once grew is difficult to establish but anyone who has stood in the midst of a few thousand acres of ripe wheat on a hot summer’s day can tell you that the albedo is indeed significant.

How global is the near-surface temperature recording coverage?

According to the NASA Goddard Institute for Space Studies (GISS) Surface Temperature Analysis page, not very:

“The Figures below indicate:
(a) the number of stations with record length at least N years as a function of N ,
(b) the number of reporting stations as a function of time,
(c) the percent of hemispheric area located within 1200km (~750miles) of a reporting station.

”

Compared with the near-global coverage of NOAA satellite-mounted MSUs (the “satellite record”), reporting stations on a grid of about 1500miles is not particularly good coverage. Given that so many near-surface stations are located in urban settings and even airports it is unavoidable that the near-surface record is affected by UHIE.

Could UHIE create the illusion of “global warming’?

It is difficult to see how it could not. The late John L. Daly explored this problem in a report to the Greening Earth Society “The Surface Record: Global Mean Temperature and how it is determined at surface level”

Is UHIE the reason for the increasing discrepancy between the MSU record and GISS GISTEMP?

As the above graph indicates, the only time in the last decade that agreement between the records has improved was when the troposphere reacted to the powerful 1997/98 El Nio event. With the MSU record in good agreement with data from radio-sonde balloons and satellite-mounted instruments giving significantly greater global coverage than the GISTEMP near-surface record it seems reasonable to wonder whether most recorded warming is global or merely urban.

The global temperature report for July 2004 from the University of Alabama in Huntsville (USA) Earth System Science Center found that July 2004 was the planet’s coolest month in four and a half years and the coolest July in a dozen years.
 
The data show that the global temperature was 0.21C (about 0.38F) below the 20-year average for July.  This followed on from a June temperature about 0.02C below the average.  Only 3 months in the last 41 had been below this norm.
 
Dr. John Christy of UAH said, This was the coolest July since 1992, when global temperatures were cooled by dust thrown into the atmosphere by the Mount Pinatubo volcano.  A color map of temperature anomalies will be available at http://climate.uah.edu/ .
 
Regardless, new studies purportedly supporting alarmist, regional claims in the U.S. and Europe have been based on outputs from two models, including the Hadley Center Model, which reviewers admitted during the course of the National Assessment on Climate Change performed no better than a table of random numbers in predicting past climate.
 
One such study, Emissions pathways, climate change, and impacts on California, published in the August 24 issue of Proceedings of the National Academy of Sciences garnered considerable press coverage in California and the rest of the nation on August 17.  The Associated Press coverage was typical:
 
Global warming could cause dramatically hotter summers and a depleted snow pack in California, leading to a sharp increase in heat-related deaths and jeopardizing the water supply, according to a study released Monday.
 
Under the most optimistic computer model, periods of extreme heat would quadruple in Los Angeles by the end of the century, killing two to three times more people than in heat waves today; the Sierra Nevada snow pack would decline by 30% to 70%; and alpine forests would shrink 50% to 75%.
 
The most pessimistic model projects five to seven times as many heat-related deaths in Los Angeles, with six to eight times as many heat waves.  Snow pack and high altitude forests would shrink up to 90%.  The scientists’ temperature projections are higher than previous estimates, particularly in summer. Their predictions of an extreme decline in snow pack, alpine forests and the spread of desert areas all exceed earlier projections.
  
In addition to its “random numbers problem”, the model was run on the basis of data from the discredited SRES scenarios of the Intergovernmental Panel on Climate Change that predict countries such as Zimbabwe, Vanuatu and North Korea overtaking the USA in per capita income by 2100.  There was no discussion of the appropriateness or robustness of these data choices in the published paper.

It’s Hurricane Season and the claims are escalating faster than the storms. Already we’ve had Knight Ridder Newspapers claiming “The past nine years, from 1995 through 2003, mark the busiest, most intense nine-year storm period on record” based, apparently, on this Climate Prediction Center graphic. Of course, if you choose your “record” carefully enough you can prove anything – but it is not necessarily instructive to do so.

The National Hurricane Center provides a somewhat longer perspective online in U.S. Hurricane Strikes by Decade. From that table it is a simple matter to create a pretty graphic. The thumbnail at right links to a stacked column graph of U.S. landfalling hurricanes by Saffir-Simpson Category and decade. Counts are not labeled for category 5 storms, one occurring in each of the 30s, 60s and 90s (with Hurricane Andrew [1992] having been escalated from cat 4 to cat 5 on reanalysis in 2002).

On a raw count it appears the 1940s were pretty active while the 1970s were rather quiet. Naturally this doesn’t necessarily mean that the ferocity of these storms are comparable so we need to differentiate by some sort of composite rating.

A quick check on the numbers of more severe storms (cat 3-5), already tallied for us on the linked NHC page, indicates a similar high/low pattern but it would be nice to have something better than simple raw counts. How about using the storms’ Saffir-Simpson Category as a point system? This will give us an instant weighting system so we can accumulate both the number and severity of storms in any given decade – think of it as a sort of decadal hurricane ferocity score.

Perhaps an activity rating would be the more accurate description because the second half of the Twentieth Century does not appear as ferocious as the first.

Granted, this is a very rudimentary analysis but it does suffice to demonstrate the effect of record selection. It is entirely possible, in fact probable, that the Climate Prediction Center has only that length of record with sufficient data to perform their total energy analysis but it does not justify Knight Ridder‘s claim of “busiest, most intense” period on record.

According to The Most Intense Hurricanes in the United States 1900-2000 only 28 of the listed 65 events occurred since 1950. The Deadliest, Costliest, And Most Intense United States Hurricanes From 1900 To 2000 (And Other Frequently Requested Hurricane Facts) indicates that fully half the years when no hurricanes struck mainland U.S. are after 1950 (10 of 19). The most hurricanes to strike in one year were six in 1916 and 1985. There were five in 1933, and four in 1906, 1909, and 1964. Three hurricanes struck the U.S. in one year a total of sixteen times. Ten of these sixteen times occurred during the sixteen years from 1944 to 1959.

It would appear our rough and ready activity rating scheme of allocating and accruing points by Saffir-Simpson Category adequately reflects the relative severity of the hurricane cycle. While not fully represent the energy of the season a total event count obviously gives a rough approximation of the season severity.

The one thing we did not find is any suggestion of increasing hurricane season severity. The most active period within the Twentieth Century record is the 1930s-1960s with something of a lull subsequently. This is not supportive of the hypothesis that the globe is warming catastrophically or that there are more and more severe storms occurring.