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Lloyd

On Feb 26, 12:46 am, "B00ZN" wrote:
Measuring The Phoenix Urban Heat Island

22 Feb 2008

http://www.climate-skeptic.com/2008/...reing-the.html

This is a project my son did for Science Fair to measure the urban heat
island effect in Phoenix. The project could also be called "Disproving
the IPCC is so easy, a child could do it."

The IPCC claims that the urban heat island effect has a negligible
impact, even on surface temperature stations located within urban areas.

After seeing our data, this claim will be very hard to believe.

In doing the test, we tried to follow as closely as possible the process
used in the Nyuk Hien Wong and Chen Yu study of Singapore as published
in Habitat International, Volume 29, Issue 3 , September 2005, Pages
547-558. We used a LogTag temperature data logger. My son used a map
and a watch to mark our times, after synchronizing clocks with the data
logger, so he could match times to get temperature at each location. I
called out intersections as we passed them and he wrote down the times.
At the same time, I actually had a GPS data logger where I gathered GPS
data for location vs. time, but I did not share this with him because he
wanted to track locations himself on the map. My data below uses the
GPS data, which was matched with the temperature data in an Excel
spreadsheet using simple Vlookup calls.

To protect the data logger from the 60mph wind (we tried to drive at
exactly 60 so my son could interpolate distances between intersections)
we put the datalogger in a PVC Tee:

We added some insulation to reduce the effect of heat from the car's
roof, and then strapped the assembly to the roof with the closed part of
the Tee facing forward (the nose of the car is to the left in this
picture).

We drove transects two nights in a row. Both nights were cloudless with
winds below 5 mph. Ideally, we would have driven between midnight and 6
AM, but this was my kid's science project and he needs to get to bed so
we did it from about 9PM to 11PM. We were concerned that the air might
still be cooling during the test, such that as we drove out from town,
it might be easy to mix up cooling with time and cooling with location.
Our idea for correcting this was to drive and gather data on an entire
loop, starting in the center of town, going about 30 miles out, and then
returning to the starting point. That way, with data taken in both
directions, the results could be averaged and the cooling rate would
cancel out. As it turned out, we didn't even bother to do the
averaging. The two trips can be seen in the plots, but the urban heat
island shows through pretty clearly in the data and the slope of the
line between temperature and distance was about the same on the inbound
and outbound legs.

I used the GPS lat/long points to calculate the distance (as the crow
flies) from the center of town (My son did it the hard way, using a tool
on Google maps).

The first night we went north (click to enlarge):

The second night we went south. The urban profile going south is a
little squirrellier, as the highway we were traveling tends to dip in
and out of the urbanization.

Here is the total route over the two nights. I'm still trying to figure
out the best way to plot the temperatures on the map (again, click to
enlarge)

You can see the results. Even at the too-early time of 9-11PM, the
temperature fell pretty linearly by about 0.2-0.3 degrees F per mile
from the city center (as the crow flies).

I would really love to do is to go down to Tucson and run this same test
starting at the USHCN weather station there and driving outwards. That
may have to wait a few weeks until my job calms down a bit.

Update: Per some emails I have received, it is theoretically possible
for the urban heat island effect to be real and to have integrity in the
surface temperature record. The first way this could happen is if the
official measurement stations are well sited and outside of growing
urban heat islands. I know for a fact by direct observation that this
is not the case. A second way this might be the case is if one argues
that urban heat islands exist but their effect is static over time, so
that they may bias temperatures but not the warming signal. I also
don't think this is very credible, given growth of urban areas over the
last 50 years.

A better argument might be that because most US temperature stations are
arriving at daily temperature averages from just measuring daily min and
max temperatures. It might be arguable that while urban temperatures
cool more slowly at night, they still reach the same Tmin in the early
morning as the surrounding countryside. Unfortunately, I do not think
this is the case -- studies like this one taken at 5AM have seen the
same results. But this is something I may pursue later, redoing the
results at whatever time of day Phoenix usually hits its minimum
temperature.

A good argument for the integrity of the surface temperature measurement
system is NOT that scientists blind to local station installation
details can use statistical tools to correct for urban biases. After
looking at two stations in the Arizona area, one urban (Tucson) and one
rural (Grand Canyon) it appears the GISS statistical method, whatever
this double-secret process may be [insert rant about government-funded
research by government employees being kept secret] it actually tends to
average biased sites with non-biased sites, which does nothing to get
the urban bias out of the measured surface warming signal - it just
spreads it around a little. It reminds me a lot of my kids spreading
the food they don't like in a thin layer all over the plate, hoping that
it will be less noticeable than when it sits in one place in a big pile.

Again, I have not inspected their procedure, but looking at the results
there seems to be a built-in assumption in the GISS algorithms that they
expect an equal chance of a site being biased upwards vs. downwards. In
fact, I seem to see more GISS corrections fixing imagined downwards
biases than upwards biases. I just don't see how this is a valid
assumption. The reality is that biases in outdoor temperature
measurement are much more likely to be upwards than downwards,
particularly over the last 50 years of urbanization and even more
particularly given the fact that the preferred measuremnt technology,
the MMTS station, has a very very short cable length that nearly
gaurantees an installation near buildings, pavement, etc.

Update #2: To this last point, consider this situation: Thermometer
one in the city shows 2 degrees of warming. Thermometer two a few
hundred kilometers away shows no warming. Someone aware of urban biases
without a dog in the hunt would, without other data to guide them,
likely put their money on the rural site being correct and the urban
site exaggerated or biased. The urban site should be thrown out, not
averaged in. However, the folks putting the GISS numbers together are
strong global warming believers. They EXPECT to find warming, so when
looking at the same situation, absolutely sure in their hearts there
should be warming, the site with the 2 degrees of warming looks correct
to them and the no warming site looks anomalous. It is for this reason
that the GISS methodology should be as public as possible, subject to
full criticism by everyone.

--

Regards

Bonzo

"The notion of a static, unchanging climate is foreign to the history of
the earth or any other planet with a fluid envelope. The fact that the
developed world went into hysterics over changes in global mean
temperature of a few tenths of a degree will astound future
generations." Richard Lindzen, Professor of Meteorology MIT and Member
of the National Academy of Sciences

Read http://en.wikipedia.org/wiki/Urban_heat_island

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