Global warming pushers should be choking on soot this week. Instead, the global warming-friendly media is choking a potentially devastating story.

"Soot may be responsible for fifteen to thirty percent of global warming, yet it's not even considered in any of the discussions about controlling climate change," says Stanford University professor Mark Jacobson. 

The familiar black residue coating fireplaces and darkening truck exhaust is second in importance only to carbon dioxide as a cause of global warming, according a study by Jacobson's published this week in the prestigious journal Nature

Though Nature issued a news release to spotlight the study, no major media outlet reported it — not the Associated Press, Washington Post, or New York Times, all of whom typically miss no opportunity to trumpet gloom-and-doom stories about global warming. 

But that's the problem. Jacobson's study raises serious questions about the theory that humans are measurably changing global climate. 

Jacobson ironically offers the study as a reason to accelerate efforts to control global warming. But his study actually illustrates the utter folly of the Kyoto Protocol — the 1997 treaty not yet ratified by the U.S. Senate, which calls for drastic reductions in carbon-dioxide emissions (read "energy use") among developed nations with the aim of avoiding climate-related calamities. 

Global-warming alarmists claim humans are raising global temperatures by burning oil, gas and coal. Such combustion releases carbon dioxide into the atmosphere. The added "greenhouse gas" absorbs solar radiation, thereby "unnaturally" warming the atmosphere. 

Unchecked carbon-dioxide emissions will cause global temperatures to rise by as much as 10.4 degrees Fahrenheit over the next 100 years, according to the alarmist United Nations' Intergovernmental Panel on Climate Change (IPCC). This temperature increase is predicted to cause all sorts of problems, from severe weather-related events to higher sea levels to the spread of infectious diseases. 

The predicted rise in global temperature is not based on scientific evidence, but rather on mathematical models that rely on crude assumptions about the numerous and complex factors that affect global climate. 

The IPCC explicitly admits a lack of knowledge about climate factors, stating that there is "low" or "very low" scientific understanding of nine of the 12 factors thought to affect global climate. For two factors, there is "medium" understanding. The IPCC says there is a "high" level of understanding only for the greenhouses gases, such as carbon dioxide, methane, and nitrous oxide. 

Enter soot. 

The IPCC acknowledges soot may affect climate but downplays it anyway. The IPCC classifies soot in the "very low" category of scientific understanding and says that soot isn't a very potent trapper of solar radiation. 

But Jacobson says that soot combines in the atmosphere with dust, sea spray, atmospheric aerosols and chemicals. The resultant particles — call them "soot-plus" — absorb much more solar radiation than plain soot. 

The IPCC hypothesizes carbon dioxide is the most important contributor to global warming, trapping solar radiation at a rate of 1.56 Watts per square meter. Methane is rated second by the IPCC at 0.47 Watts per square meter. Jacobson estimates the rating for soot-plus is an astounding 0.55 Watts per square meter. 

Here's how soot-plus is a show-stopper. 

There is general agreement that global temperatures warmed from 1910 to 1940 and cooled from 1940 to 1975. Temperature changes since 1975 are hotly disputed. The IPCC says global temperatures have warmed. But this claim is based on surface temperature records that are biased upwards by temperature readings from urban areas where concrete and asphalt absorb heat. 

Other climatologists point to satellite and balloon temperature measurements that are unaffected by the so-called "urban heat island effect" and report no significant warming global warming since 1979. 

So despite the steady increase in atmospheric greenhouse gases during the 20th century, there has been significant no warming trend since 1940. 

The IPCC tries to account for this discrepancy by saying an increase in atmospheric aerosols — dust from volcanic eruptions and sulfates from fossil fuel that reflect solar radiation — masked the post-1940 warming effect of the greenhouse gases by providing a cooling force in the atmosphere. 

Accepting the IPCC's explanation for the sake of argument, the heretofore ignored existence of soot-plus exactly offsets the cooling effect of the aerosols — and the IPCC is back to needing an explanation for why global temperatures aren't rising with greenhouse gas concentrations. 

So the IPCC models that assume global climate is very sensitive to greenhouse gases and predict a 2.5- to 10.4-degree increase in temperature over the next 100 years remain seriously flawed. 

University of Virginia climatologist Pat Michaels says Jacobson's study bolsters his prediction of only a 2.5-degree Fahrenheit increase over the next 100 years. Atmospheric physicist S. Fred Singer says the predicted temperature increase is likely to be even less. 

The larger question, though, is how much confidence should be placed in IPCC forecasts that completely overlook possibly the second-most important manmade impact on climate? 

Under the Kyoto Protocol, carbon-dioxide emissions would be reduced to 1990 levels by 2010, which would require a 30 percent reduction in energy use. Should we reduce energy use and risk harming the economy based on predictions of global warming that are so lacking in understanding? 

Certainly more research is needed to confirm soot is the dirty secret that undoes global warming hysteria. Meanwhile, the soot-plus hypothesis should bar the rush-to-judgment the global warming pushers want us to make — if only the media would tell someone. 

— Steven Milloy is a biostatistician, lawyer and adjunct scholar at the Cato Institute and publisher of Junkscience.com.