With an unusually intense heat wave sweeping the nation, Fox News has been silent on global warming, which scientists say makes heat waves like this one more likely. By contrast, Fox News repeatedly used winter storms to mock global warming -- one of several problems with Fox's coverage of climate change highlighted in a new mini-documentary by Media Matters Studios:

Most flagrantly, Fox Nation and Fox News personalities Sean Hannity, Glenn Beck, Gretchen Carlson, Steve Doocy, Stuart Varney, and Eric Bolling all seized upon the February 2010 blizzard to mock Al Gore and suggest that the storm undermines the science supporting global warming. That same winter, Fox News Washington managing editor Bill Sammon ordered the network's journalists to cast doubt on climate change data.

In reality, that winter included “the eighth warmest December" since records began in 1880, the “fourth warmest” January, and the “sixth warmest” February according to global temperature data from NOAA. 2010 tied for the warmest year on record, and 2000-2009 was by far the warmest decade on record.

Over the past week, Fox News has not mentioned human-induced climate change or global warming while reporting on or discussing the current heat wave, according to a search of Snapstream video and Nexis transcripts.

The Washington Post reported that this “long duration, widespread heat wave continues to bake virtually the entire central U.S” and “969 daily high temperature records were either tied or broken in the country” through July 16. The Post further reported:

Climate change research indicates that manmade emissions of greenhouse gases may already be increasing the likelihood of extreme heat events like this one, including the 2003 European heat wave that killed tens of thousands. Also, recent studies have projected much hotter summers beginning as soon as just a few decades from now as the climate continues to warm. However, it will take months if not years for scientists to determine whether climate change has played a role in turning up the heat so far this summer, and in this heat wave specifically.

NASA climatologist Gavin Schmidt told Media Matters it's “very probable that any particular heat wave happening now will be shown to have become more likely because of global warming,” adding: “Of all the different extreme events that can happen, the partial attribution of heat waves to ongoing climate change is one of the easier connections.”

Schmidt explained that there are a number of questions to ask when considering whether global warming may be contributing to extreme weather events:

1) A sniff test - does it make any sense that this effect might be linked? (this doesn't mean that non-obvious things can't happen, but the burden of proof is higher).

2) Are there analyses in the scientific literature that indicate that models do in fact show a change in this extreme as a function of increasing global temperatures? Are these analyses credible? (this will depend on the scale involved, etc.), do all models show the same thing?

3) Have we seen increases in the data already? (this can be hard since the data on extremes is not very extensive).

4) Are the expected changes in the statistics commensurate with what has been seen? (i.e. if models predict a 10% increase but the increase has been 100%, then it's not clear we have understood what is going on).

In the case of heat waves, the answer to each of these questions is yes, Schmidt said.

The National Research Council explained in a recent report that heat waves are expected to become “more intense, more frequent, and longer-lasting” in the United States and around the globe as a result of human-induced climate change.

This conclusion echoes the findings of the U.S. Climate Change Science Program, which stated in a 2009 assessment of climate change impacts in the United States that “with rising high temperatures, extreme heat waves that are currently considered rare will occur more frequently in the future.” The report added:

Recent studies using an ensemble of models show that events that now occur once every 20 years are projected to occur about every other year in much of the country by the end of this century. In addition to occurring more frequently, at the end of this century these very hot days are projected to be about 10°F hotter than they are today.

Extensive long-term and global data show that the climate is warming and the recent heat wave is consistent with scientists' expectation of more frequent and longer-lasting extreme heat events. Avoiding discussion of global warming while covering the current heat wave is a bit like ignoring the economic recession while discussing mass layoffs. The climate system is shifting. Will Fox take notice?