On the August 10 broadcast of his nationally syndicated radio show, Rush Limbaugh falsely dismissed the role humans play in global warming and ozone depletion. In fact, the vast majority of the scientific community -- including the U.S. government -- has accepted for decades that chemicals released into the atmosphere by humans are responsible for depleting ozone levels around the globe. Additionally, both the Intergovernmental Panel on Climate Change (IPCC) and the National Academy of Sciences (NAS) have stated that human-caused greenhouse gases are largely responsible for global warming.

Limbaugh fiction: “We couldn't destroy the ozone layer”

Referring to the “modern environmental movement” as “the latest refuge for communists and socialists who are opposed to capitalism,” Limbaugh asserted that "[w]e couldn't destroy the ozone layer"; he also said that humans could not be at fault for the ozone hole that appears annually over Antarctica because it “closes every year, and we don't do anything to close it.”

But Limbaugh's statements contradict the opinion of the Environmental Protection Agency (EPA) and the United Nations Environmental Programme (UNEP). In a component of a report titled “Scientific Assessment of Ozone Depletion: 2002,” the World Meteorological Organization (WMO) and UNEP noted: "[I]t was discovered in the mid-1970s that some human-produced chemicals could destroy ozone and deplete the ozone layer. The resulting increase in ultraviolet radiation at Earth's surface can increase the incidences of skin cancer and eye cataracts."

Recognizing the global threat posed by ozone depletion, the Reagan administration agreed to the 1987 Montreal Protocol, which phased out chlorofluorocarbons (CFC) and other ozone depleting substances (ODS) responsible for this process.

Limbaugh referred to the protocol as follows: “It's all irrelevant to me. The ozone hole closes. When is the last time you heard the ozone hole as a big issue?” He added, “It's been years, and all we've done is drive more cars, burn more fuel. We cool and do these sorts of things.”

Yet Limbaugh is simply wrong to assert that ozone depletion is not a result of human activity. While the Antarctic ozone hole does, in fact, close every year, this does not mean that ozone depletion is not human-caused. According to the EPA, the dramatic -- though temporary -- destruction of the Antarctic ozone layer is indeed caused by the interaction of human-released ODS with local weather patterns. Moreover, scientists remain extremely concerned about the gradual depletion of global ozone levels -- a process that is not self-correcting. As the EPA notes, this worldwide process is caused by human-produced ODS and has reduced ozone levels over the United States by 5 percent to 10 percent. Worldwide, ozone levels have decreased an average of 3 percent from pre-1980 levels.

According to the EPA, scientists predict that worldwide ozone levels could be entirely replenished by 2050, provided that countries comply with the Montreal Protocol by ceasing production of ODS, but “delays in ending [ODS] production could result in additional damage and prolong the ozone layer's recovery.”

Limbaugh fiction: Global warming “one of the biggest hoaxes being perpetrated on the people of the world”

Limbaugh insisted that “environmentalists still cannot prove that this [global warming] is man-made.” To support this assertion, he claimed, “There have been too many global heating and cooling cycles long before man came along and industrialized the planet, and there have been way too many volcanoes spewing pollution that doubles the amount of the total of all the automobiles ever invented and manufactured in the world.” On the August 15 broadcast of his show, Limbaugh added that global warming is “one of the biggest hoaxes being perpetrated on the people of the world.”

Again, Limbaugh's claims are contradicted by the overwhelming weight of scientific opinion. Though natural phenomena, or “natural forcings,” have certainly caused the earth's average temperature to rise and fall in the past, the scientific consensus is that the current warming trend is unprecedented -- at least in the last millennium. In 2001, the IPCC, which was established by the WMO and UNEP, concluded in its “Third Assessment Report” (TAR) that it is “very likely” (defined in the report as a 90 percent to 99 percent chance) that “the 1990s was the warmest decade, and 1998 the warmest year, in the instrumental record (1861-2000).” Moreover, it is “likely” (defined as a 60 percent to 90 percent chance) that "[t]he increases in surface temperature over the 20th century for the Northern Hemisphere" were “greater than that for any other century in the last thousand years.”

Limbaugh's suggestion that volcanoes are primarily responsible for the recent rapid warming is equally baseless. In fact, scientists have concluded that volcanoes and other natural phenomena cannot account for the dramatic increase in global temperatures over the past half-century. According to the IPCC's TAR, which reviewed a wide array of scientific work, “Simulations of the response to natural forcings alone (i.e., the response to variability in solar irradiance and volcanic eruptions) do not explain the warming in the second half of the 20th century.” The report included a graph that illustrates this divergence of actual temperature changes since 1950 (observations) from those predicted by models based entirely on natural causes (model results):

The IPCC did note, however, that when the effects of human-released greenhouse gases were added into the temperature change models, the results closely mirrored observed temperature changes:

Citing multiple studies that demonstrated this “evidence for an anthropogenic [human-caused] signal in the climate record of the last 35 to 50 years,” the IPCC stated, “There is new and stronger evidence that most of the warming observed over the last 50 years is attributable to human activities.”

The IPCC is not alone in this assessment, as Media Matters for America has previously noted. A 2001 NAS report commissioned by the Bush administration found that greenhouse gases released by human activities are “causing surface air temperatures and subsurface ocean temperatures to rise.”

While it may not be possible to “prove” that humans cause global warming, the overwhelming weight of scientific evidence has convinced even the Bush administration to acknowledge that “the surface of the Earth is warmer and an increase in greenhouse gases caused by human activity is contributing to the problem.”

From the August 10 broadcast of The Rush Limbaugh Show:

CALLER: So you don't believe in global warming?

LIMBAUGH: No.

CALLER: Or the large ozone hole?

LIMBAUGH: I, ah, no, wait, wait, wait, oh --

CALLER: Or that humans created the ozone -- destruction of the ozone?

LIMBAUGH: No. No, no, no. I don't because the hole closes every year, and we don't do anything to close it. Ah, so how are we causing it? It's the same thing --

[...]

LIMBAUGH: So 20 years has gone by, and the environmentalists still cannot prove that this is man-made. They cannot prove that the current warming cycle that I admit we're in, can be proved to be man-made and even man-caused. There have been too many global heating and cooling cycles long before man came along and industrialized the planet, and there have been way too many volcanoes spewing pollution that doubles the amount of the total of all the automobiles ever invented and manufactured in the world.

[...]

LIMBAUGH: I think the modern environmental movement is simply the latest refuge for communists and socialists who are opposed to capitalism.

[...]

LIMBAUGH: We couldn't destroy the ozone layer if we -- we would have to put out the sun. We would have to find a way to send fire trucks to the sun and put it out.

CALLER: Then what was the point of the Reagan signing the Montreal Protocol, you know, ending CFC production? Or restricting it at least?

LIMBAUGH: Uh ... it's all irrelevant to me.

CALLER: It is.

LIMBAUGH: The ozone hole closes at -- when's the last time you heard about the ozone hole's a big issue?

CALLER: Nah, but that's all --

LIMBAUGH: It's been years. And all we've done is drive more cars, burn more fuel, we cool and do these sorts of things.