From Roger Pielke Sr.
A very good news article titled Expanding cities contribute to global warming by Doyle Rice has been published on USA Today.
The article is based on our paper
Fall, S., D. Niyogi, A. Gluhovsky, R. A. Pielke Sr., E. Kalnay, and G. Rochon, 2009: Impacts of land use land cover on temperature trends over the continental United States: Assessment using the North American Regional Reanalysis. Int. J. Climatol., DOI: 10.1002/joc.1996.
The USA Today article reads
The USA’s expanding cities and suburbs are contributing more to global warming than previously thought, says a new study in the Royal Meteorological Society’s International Journal of Climatology.
“We found that most land-use changes, especially urbanization, result in warming,” said study co-author Eugenia Kalnay of the University of Maryland.
Most scientists believe man-made climate change is primarily the result of increasing concentrations of carbon dioxide (CO2) and other greenhouse gases into the atmosphere. So, does this mean rising temperatures due to greenhouse gases are less significant? No, say study authors.
“I think that greenhouse warming is incredibly important, but land use should not be neglected,” Kalnay said. “It clearly contributes to warming, especially in urban and arid areas.”
As for how much it contributes, compared to greenhouse gases, “we cannot provide a specific percentage,” writes study co-author Roger Pielke, Sr., of the University of Colorado in an e-mail. “But our results suggest that land-use change can affect surface temperatures as much or more than what has been simulated by the global climate models as being due to added CO2 from human activities.”
The study recommends that the predicted land-use changes be incorporated into the computer models designed to forecast changes in climate conditions. This is key, according to study co-author Dev Niyogi of Purdue University. He said that even with aggressive green emission controls, warming will still continue unless how we use the land is considered.
“Continued temperature changes will occur as long as the landscape continues to be altered,” added Pielke. “The subject of the effect of future land use change on local and regional climate should be a major focus of upcoming climate assessments.”
Among the study’s findings:
– Land use conversion more often results in warming than cooling.
– Urbanization and conversion to bare soils have the largest warming impacts.
– Conversion to agriculture results in cooling, while conversion from agriculture generally results in warming.
– In general, the more the vegetation covers an area of land, the cooler its contribution to surface temperature.
– Deforestation generally results in warming, with the exception of a shift from forest to agriculture
– The temperature effect of planting a new forest is unclear.