Study Documents False Warming Trend

Study Documents False Warming Trend
June 1, 2003

James M. Taylor, J.D.

James M. Taylor is managing editor of Environment & Climate News, a national monthly... (read full bio)

A newly published study of the Houston, Texas urban heat island effect may resolve one of the most controversial debates in climate change science: Which provides a more accurate reading of the Earth’s global temperature, satellite readings or ground-based readings?

Results of the new study suggest satellite readings, which show no warming since 1979, are more accurate than ground-based readings showing significant warming.

Contrasting Temperatures

Ever since the first temperature-reading satellite was launched in 1979, scientists have tried to explain the discrepancy between satellite and ground-based readings of global temperatures. Satellite readings have shown no warming since 1979, while ground-based readings have registered significant warming.

The national media repeatedly trumpet each year’s apparently warm temperatures, as measured by ground-based stations, failing to mention that satellites show no warming. Global warming alarmists acknowledge the satellite readings but say they may not accurately reflect warming at the Earth’s surface ... even though their own theories and computer models predict the lower atmosphere will show the first signs of global warming.

Many climate scientists, however, believe the satellite readings are precise and accurate, while ground-based readings are subject to artificial warming factors, such as the effect of urban development around land-based weather stations.

Heat Island Growth

In the May 30 issue of Remote Sensing of Environment, a research journal for environmental scientists, Rice University Department of Physics and Astronomy researcher David Streutker compared two sets of temperature measurements, taken 12 years apart by polar-orbiting satellites launched by the National Oceanic and Atmospheric Administration. The satellites measured 82 nighttime temperature readings in Houston and its surrounding environment between 1985 and 1987, and then took another 125 nighttime readings between 1999 and 2001.

The satellite readings allowed Streutker to analyze temperature changes over time in Houston and its surrounding environment. Over the 12-year interval, temperatures in Houston showed significantly more warming than temperatures in the area surrounding the city.

According to Streutker, “over the course of 12 years, between 1987 and 1999, the mean nighttime surface temperature heat island of Houston increased 0.82 ± 0.10 [ºC].” Streutker further reported, “the growth of the UHI [urban heat island], both in magnitude and spatial extent, scales roughly with the increase in population, at approximately 30%.”

Heat Islands Eclipse Warming

The increase in the Houston urban heat island effect of nearly a full degree Celsius between 1987 and 1999 is remarkable in that ground-based temperature readings, unadjusted for heat island effects, indicate less than 1 degree of warming during the entire twentieth century. In other words--unless Houston can be shown to be atypical--localized, artificial heat islands explain the entirety of twentieth century warming reported by ground-based temperature stations, and may even be obscuring a slight cooling trend.

Just as importantly, the study indicates satellites have been giving accurate temperature readings, showing no warming since 1979, while ground-based stations have falsely reported a string of years with record-breaking warm temperatures.

“This extremely well-designed study has probably characterized the development of the urban heat island of Houston, Texas better than has ever been done before for any city on Earth,” reported Sherwood Idso, president of the Center for the Study of Carbon Dioxide and Global Change (http://www.co2science.org), “and, in so doing, it has demonstrated that the growth of the [urban heat island effect] ‘scales roughly with the increase in population.’

“What is more, it demonstrates that this phenomenon is huge. In just 12 years, the UHI of Houston grew by more than the IPCC calculates the mean surface air temperature of the Earth rose over the entire past century, over which period the Earth’s population rose by some 280 percent, or nearly an order of magnitude more than the 12-year population growth experienced by Houston.

“Given these facts,” added Idso, “it is presumptuous in the extreme to believe that the global surface air temperature record of the last two decades of the twentieth century--when world population rose by over 35 percent--could ever be accurately enough ‘massaged’ to provide a realistic assessment of what the planet’s non-urban-affected surface air temperature really did over that period. Hence, like it or not, we are essentially forced to rely on the satellite record when it comes to evaluating contemporary global climate change; and that record suggests that the warming of that period--if there truly was any at all--was a far cry from the ‘unprecedented’ status that climate alarmists are fond of attaching to it.”

Evidence Mounting

The Houston study is in agreement with research published in the March 2001 issue of Australian Meteorological Magazine also documenting a heat island effect.

The Australian study suggested that even very small towns, with populations measured in mere hundreds of inhabitants, produce significant urban heat island effects.

“With such small aggregations of people having such a dramatic impact on air temperature, it is ludicrous to believe that on top of the natural warming experienced by the Earth in recovering from the Little Ice Age we can confidently discern an even more subtle increase in background temperature caused by concomitant increases in greenhouse gas concentrations,” reported the Center for the Study of Carbon Dioxide and Global Change.

“Changes in population, which have generally been positive nearly everywhere in the world over this period, could easily explain whatever tiny bit of warming is left after the natural component of warming (which must be substantial, relatively speaking) is subtracted from the total amount of warming recorded by the totality of Earth’s thermometers over the past century or so.”


James M. Taylor is managing editor of Environment & Climate News.


For more information ...

David Streutker’s “Satellite-measured Growth of the Urban Heat Island of Houston, Texas,” published in Volume 85, Number 3 (May 2003) of Remote Sensing of Environment is available for $30.00 online at http://www.sciencedirect.com/science/journal/00344257.

James M. Taylor, J.D.

James M. Taylor is managing editor of Environment & Climate News, a national monthly... (read full bio)