By EurekAlert
Tuesday, November 3, 2009
WEST LAFAYETTE, Ind. ╤ Researchers say regional surface
temperatures can be affected by land use, suggesting that local and
regional strategies, such as creating green spaces and buffer zones
in and around urban areas, could be a tool in addressing climate
change.
A study by researchers from Purdue University and the
universities of Colorado and Maryland concluded that greener land
cover contributes to cooler temperatures, and almost any other
change leads to warmer temperatures. The study, published on line
and set to appear in the Royal Meteorological Society's
International Journal of Climatology later this year, is further
evidence that land use should be better incorporated into computer
models projecting future climate conditions, said Purdue doctoral
student Souleymane Fall, the article's lead author.
"What we highlight here is that a significant trend,
particularly the warming trend in terms of temperatures, can also
be partially explained by land-use change," said Dev Niyogi, a
Purdue earth and atmospheric sciences and agronomy professor, and
the Indiana state climatologist. He is the study's corresponding
author.
Niyogi and Fall say the idea that land use helps drive climate
change has been poorly understood compared to factors such as
greenhouse gas emissions. But that is changing.
"People realize that land use cover also is an important force
and not only at the local but also at the regional scale," said
Fall, whose doctoral research focuses on the impacts of land
surface properties on near-surface temperature trends.
The researchers used higher resolution temperature data than
previous studies, meaning the data was more detailed, Niyogi said.
They also employed dynamic data on land-use changes from 1992-2001,
which was derived from satellite imagery.
Niyogi said having an understanding of land use's affects on
climate change could have climatic and other benefits. For
instance, creating green spaces and buffer zones in and around
urban areas also could be aesthetically attractive, he said.
Among the study's findings:
- In general, the greener the land cover, the cooler is surface
temperature.
- Conversion to agriculture results in cooling, while conversion
from agriculture generally results in warming.
- Deforestation generally results in warming, with the exception
of a shift from forest to agriculture. No clear picture emerged
from the impact of planting or seeding new forests.
- Urbanization and conversion to bare soils have the largest
warming impacts.
In general, land use conversion often results in more warming
than cooling.
The study took an approach called "observation minus
reanalysis," or OMR. Through this process, the researchers used
temperature data from local ground observations, observation and
computer modeling, Geographic Information Systems (GIS) and
statistical methods. They were able to separate the effects of land
use or cover from greenhouse warming and isolate the impact from
each land use or cover type. The more detailed data provided a
clearer picture of the effects of land surface properties on
near-surface temperature trends.
"We showed this quantitatively for the first time," said
University of Maryland atmospheric and oceanic science Professor
Eugenia Kalnay, who developed the OMR method with Florida State
University Professor Ming Cai. She also is a co-author of the
study.
While the effects of greenhouses gases like carbon dioxide are
clear, Kalnay said, the study does suggest land use needs to be
considered carefully as well.
"I think that greenhouse warming is incredibly important, but
land use should not be neglected," she said. "It contributes to
warming, especially in urban and desertic areas."
Another study co-author, Roger Pielke Sr., said the results
indicate that "unless these landscape effects are properly
considered, the role of greenhouse warming in increasing surface
temperatures will be significantly overstated." Pielke is a senior
research scientist in atmospheric and oceanic sciences at the
Cooperative Institute for Research in Environmental Sciences and
the Department of Atmospheric and Oceanic Sciences at the
University of Colorado in Boulder.
SOURCE