• We developed a method to estimate the impact of land-use change (including urbanization and agriculture) on surface temperatures

• We compare the surface observations with the NCEP 50 year Reanalysis, which is insensitive to land-use change

• Obtained that the impact of land-use changes is comparable in magnitude to that of greenhouse gases.

Impact of urbanization and land-use on climate change

Eugenia Kalnay and Ming Cai(Nature, 2003)

Issues:

• The two most important anthropogenic activities that impact climate:

1. increase of greenhouse gases

2. changes in land use

• They both tend to produce surface warming so that their impacts are very difficult to separate.

• The impacts of changes in land use have been regarded as “noise”, compared to impacts of increase of greenhouse gases.

1950’s:Tob-Tan=0.0

1960’s:Tob-Tan=0.61

1970’s:Tob-Tan=0.60

1980’s:Tob-Tan=0.80

1990’s:Tob-Tan=1.40

Example: Baltimore City, MD

With time, the observations (in red) become warmer than the reanalysis (in blue).We attribute the difference in the trends, at least partially, to urbanization and other land-use changes.

OBS

REANAL

OBS - REANAL

and attribute the difference to land-use changes

We do it for each station

Land-use changes over the US explain:

• About 40% of the observed increase in Tmin

• Most of the observed decrease in Tmax

• Half of the decrease in diurnal temperature range (-0.14 out of –0.28 C/decade)