If you'd like to catch up on the discussion to date, you can read Part One of this series here, Part Two here, and Part Three here.

A recent report in Canada’s National Post reads “The polar ice cap is shrinking, laying bare deep gullies in the landscape and the climate is the warmest it has been in decades or perhaps centuries.” Sounds scary, doesn’t it? Well it is if you’re a Martian! According to NASA, data collected from the Mars Odyssey mission reveals that Mars is also experiencing “global warming.” NASA scientist William Feldman said, “In some low-latitude areas, the ice has already dissipated.” Following a recent analysis of the first twelve months of data collected from Mars, scientists are accumulating evidence that climatic changes similar to Earth’s are also occurring on the only other planet in the solar system where climate is now being studied.

Now, the obvious question is “How can Mars experience global warming if global warming is caused by an increase in carbon dioxide produced by human industry?”

According to the proponents of “man-made” global warming, carbon dioxide emissions are the culprit in climate change. So what is the role of carbon dioxide if any and are there other, more plausible explanations for the half-degree centigrade temperature increase that is believed to have occurred over the last century?

Astrophysicist Nir Shariv, one of Israel’s top scientists, was once a proponent of the theory that man-made carbon emissions are driving climate change.  In an interview with Lawrence Solomon, a columnist for the National Post, Dr. Shariv “described the logic that led him -- and most everyone else -- to conclude that SUVs, coal plants and other things man-made cause global warming.” Dr. Shariv points out that “scientists for decades have postulated that increases in carbon dioxide and other gases could lead to a greenhouse effect.” Then, as if on cue, “the temperature rose over the course of the 20th century while greenhouse gases proliferated due to human activities” and since “no other mechanism explains the warming… greenhouses gases necessarily became the cause.”

Recently however, he has recanted saying: “Like many others, I was personally sure that CO2 is the bad culprit in the story of global warming. But after carefully digging into the evidence, I realized that things are far more complicated than the story sold to us by many climate scientists or the stories regurgitated by the media.” As Dr. Shariv began to dig into the issue he was surprised to discover “there is no concrete evidence -- only speculation -- that man-made greenhouse gases cause global warming.”

Solomon points out, “Even research from the Intergovernmental Panel on Climate Change (IPCC) -- the United Nations agency that heads the worldwide effort to combat global warming -- is bereft of anything here inspiring confidence. In fact, according to the IPCC’s own findings, ‘man’s role is so uncertain that there is a strong possibility that we have been cooling, not warming, the Earth. Unfortunately, our tools are too crude to reveal what man’s effect has been in the past, let alone predict how much warming or cooling we might cause in the future.’”