Saturday, January 09, 2010

Population Density and Global Warming

It has often been observed that the center of a city is warmer than the surrounding countryside. Thus the claim has been made that global warming is an error due to weather stations gradually being taken over by urbanization. As detailed in previous posts, I've been unable to demonstrate that from the weather station data available from NASA.

The hypothesis I address on this occasion is that idea that population density in a country could be used as a proxy of urbanization. If so, then there should be a correlation between population density change over time and the temperature in that region.

I used population density figures from the CIA World Fact Book and assumed an exponential decline in density from that time depending on time:

D = d*((100-g)/100)*exp((year-2008)/127)

where D = population density in a given year
d is the population density in 2008
g is the %growth in population in 2008
year is the year of measurement.

Thus D decreases in a log linear fashion over time proportional to the rate of growth observed in 2008, an attempt to mimick population growth.

Plugging this group into the random effects statistical algorithm used in previous posts, I found no relationship between D and temperature in 60 randomly selected countries:

The x axis is the log of D (population density) and the y axis is degrees C.

No effect of population density over time emerges with this analysis.