Forest and City NY Temperatures
An interesting consideration regarding the global warming issue is the effect of local terrain.
The site (please see footnote) :
http://www.co2science.org/center.htm
includes U.S. climate data using which you can make plots to study any aspect of this
issue which interests you :
http://www.co2science.org/ushcn/ushcn.htm
I did this to a small extent, and some of my preliminary findings are interesting and
surprising. As an example, I compared the existing data for 2 locations in NY - New York
City (NYC) and Indian Lake (IL). The latter is a town well embedded in the south central
Adirondacks, near Lake Adirondack. Using its coordinates of 43.76 °N, 74.29 °W & 1660
feet elevation, the surrounding terrain can be seen quite well here. I've never been there,
so can't provide specifics regarding the type of vegetation, soil, etc. - though I imagine
it is in the middle of a largely forested region.
To determine something about a warming climate, the most logical choice is first plotting
average temperatures for the entire station histories. Though the plot for NYC shows the
expected 4 °F increase since the beginning of industrialization :
that for IL shows a 1° decrease during the 20th century :
Among the many things which may be responsible for this, those which seem most likely to
me are effects of urbanization and vegetation. During these same periods, a small increase
of annual average precipitation is noted at NYC :
and no significant change at IL :
Note that these trends are determined using linear regression, and though the temperature
trends above are quite apparent, those for precipitation (being much more variable) are
less so.
Examining maximum and minimum temperatures, it can be seen that though both increased for
NYC - minimum not quite so much as maximum :
the maximum decreased quite significantly at IL, but the minimum slightly increased :
This is characteristic of the urbanization and vegetation effects, though mentioned here is
that an attempt was made to remove "biases" in the data becuase of the effects of urbanization
(and other sources such as moving the station). Adjustments for IL are probably small, though
those for NYC may be masking a much larger increase. Seeing the actual data would be much
better - maybe I can do this sometime later.
Though the NYC July maximum increased comparably with the annual average :
that for IL decreased 5° ! :
An average maximum of 80° seems awfully high for 1660 feet in the Adirondacks - perhaps the
instrment shelter was improved during the years to minimize the effects of solar radiation on
the readings - though the more sensitive modern thermometers should increase maxima slightly.
If the cooling effect of more abundant vegetation in the Adirondacks (which an increase of
CO2 probably would cause) is responsible, it should be apparent in data for other months.
For comparison, I show plots for April, December, and January :
Though the large change is lacking for April & December as suspected, the decrease for
January is as large as July's. I suppose this indicates that too much should not be assumed
from the July plot - vegetation effect is insignificant during January. There could be many
reasons why that is so much colder - probably because of snowfall trends and/or synoptic
climatology. I.e., a slight shift of wintertime flow regimes. This could be responsible
for the summertime trend also, though flow regimes tend to be much weaker and less
significant then. Thus I think the vegetation effect is the likely cause - something
which is clearly apparent to me in the Poconos.
Several particularly noteworthy periods occurred here since I've taken observations. Though
maxima were more variable, minimum temperatures were between 61 & 68° each day from July 16
to August 1, 1999 (July 1999 data, August 1999 data). They were also very consistent during
July 2001 - most often between 53 & 60°. In this largely forested area, the vegetation
seems to act as a temperature control.
During the past 3 years, some of the warmest days of the year were during "spring" (May 2000,
May 2001, April 2002). This was with rather dry ground for May 2000 & 2001. Few or no leaves
were on the trees and vegetation not grown much. The midday sun is high, and days are becoming
long. During July 2000, the average maximum temperature was 71.2°, and the minimum was 57.3°.
It was a wet spring & summer, and more than 6 inches of rain fell during both June & July
(2000 monthly data). I purposely placed my mercury thermometer (which does not record brief
spikes well) in a particularly shady area that summer to see what type of readings I'd get.
It does illustrate the effect of vegetation and wet soil quite well. The 87° maxima May 7, 8,
& 9 of 2000 were the highest of the year and the 90° April 17, 2002 a good possibility also.
That is common in India before the monsoon establishes, but I suppose it is unusual here -
though there is also that tendency preventing a similar type of day to be so warm here during
summer, and the Poconos are not nearly so expansive as the Adirondacks. Central Park in New
York had a maximum of 96° April 17, 2002 - yet the lack of vegetation and warm flow aloft from
the Catskills were probably large factors. They are typically more than 6° warmer than my
location during a similar sunny day at each.
To see if a vegetation or urbanization effect may be prevalent elsewhere, I examined data for
a few other locations around NE PA and did find a small decreasing trend of temperatures for
other rural locations such as Montrose & Towanda, with increases at developed cities such as
Stroudsburg. Some global warming researchers claim that the warming trend remains significant
even after their attempts of removing the urbanization effect, though the data for Indian Lake
suggests that perhaps a location must be well removed from any large urban center to truly
note the effect. I recall that a recent NASA study using satellites showed a very slight
decrease of global temperature. Cities are still relatively small areas globally, so perhaps
it was detecting a more significant influence from the remote areas. This is (of course)
preliminary, and statements with much certainty would require much more research.
Data for embedded images :
Reference :
Easterling, D.R., Karl, T.R., Mason, E.H., Hughes, P.Y., Bowman, D.P., Daniels, R.C. and
Boden, T.A. (Eds.). 1996. United States Historical Climatology Network (U.S. HCN) Monthly
Temperature and Precipitation Data. ORNL/CDIAC-87, NDP-019/R3. Carbon Dioxide Information
Analysis Center, Oak Ridge National Laboratory, Oak Ridge, Tennessee.
Text is copyright of Joseph Bartlo, though may be used with proper crediting.
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