A Penn State study of climate change, conducted for the Pennsylvania Department of Environmental Protection, attempts to predict the 21st century impact of global warming on the Keystone State.
While a noble attempt to give citizens a heads-up on possible future climate conditions, it contains numerous scientific flaws and unsubstantiated assumptions that render the predictions useless.
Key to the report is its assumption that global warming will raise global and statewide temperatures by 3 to 7 degrees Fahrenheit (2 to 4 degrees Celsius) during the 21st century.
Investigators at Penn State’s Environment and Natural Resources Institute reached this conclusion by simply accepting the projections of United Nations computer models — models that have failed miserably to predict current climate conditions.
For example, in 2001 U.N. computer models predicted 0.2 to 0.4 degrees Celsius of global warming during the ensuing decade. We have nearly completed that decade and yet NASA satellite instruments show temperatures have been steadily declining.
Rather than warming by 0.2 to 0.4 degrees Celsius, temperatures through June 2009 have cooled by 0.4 degrees Celsius since January 2002.
The significant cooling since the U.N. issued its 2001 warming projections is merely the latest data that show no global warming crisis .
During the allegedly “unprecedented” warming of the 20th century, global temperatures rose merely 0.6 degrees Celsius. That’s far less than the 2 to 4 degree Celsius warming predicted by the U.N. and unquestioningly accepted by Penn State and the DEP.
Most of that warming occurred before 1945, at a time when humans were emitting relatively few greenhouse gases. Moreover, NASA satellite instruments show current temperatures are no warmer than temperatures in 1980, the year after the NASA satellites were first launched.
Global temperature increases have decelerated — and lately reversed course — rather than accelerating, as the proponents of global warming “cap-and-trade” legislation would lead us to believe.
The U.N. computer models give no reason why carbon dioxide emissions should suddenly cause rapid temperature increases in the 21st century when they have caused, at worst, very minimal temperature increases during the 20th century and no temperature increase during the past 30 years.
The National Climatic Data Center (NCDC) historical weather database tells a similar story regarding Pennsylvania. According to NCDC data, temperatures in the commonwealth show absolutely no trend over the past 114 years, since reliable temperature data first became available.
Pennsylvania temperatures today are no warmer than they were in the 1800s.
The report asserts that global warming will lead to declining soil moisture and more frequent summer droughts. However, NCDC data show that annual precipitation in Pennsylvania has increased by roughly 25 percent since 1895, with the summer and fall drought seasons showing the largest increase in precipitation.
As global temperatures have risen, Pennsylvania droughts have become less frequent.
This trend in Pennsylvania is consistent with global drought studies. Scientists report in a study of Northern Hemisphere soil moisture reported in the July 2004 issue of International Journal of Climatology:
“The terrestrial surface is both warmer and effectively wetter. … A good analogy to describe the changes in these places is that the terrestrial surface is literally becoming more like a gardener’s greenhouse.”
Similarly, scientists report in the May 25, 2006, issue of Geophysical Research Letters:
“An increasing trend is apparent in both model soil moisture and runoff over much of the U.S. … This wetting trend is consistent with the general increase in precipitation in the latter half of the 20th century. Droughts have, for the most part, become shorter, less frequent, and cover a smaller portion of the country over the last century.”
Still further, scientists recently reported in the Journal of Hydrology:
“Evidence indicates that summer soil moisture content has increased during the last several decades at almost all sites having long-term records in the Global Soil Moisture Data Bank.”
When computer models, programmed by people who already have a dog in the global warming fight, produce projections that are strongly and consistently contradicted by real-world climate, a prudent observer takes such projections with a grain of salt.
By failing to follow this commonsense advice, Penn State and DEP have issued very suspect predictions of future climate in Pennsylvania.
James M. Taylor is senior fellow of environmental policy at The Heartland Institute.