Two new climate studies agree: the planet is definitely getting warmer. But beyond that simple point, the two studies could not be further apart.

Global warming believer-turned-skeptic Anthony Watts -- a former TV meteorologist -- posted a new report online questioning the reliability of weather stations in the U.S. Historical Climatology Network, a 120-year-old weather system that forms one tent pole of climate measurements. As the country has evolved, building urban metropolises and airports and pouring parking lots, the weather stations haven’t moved, Watts said -- and poorly sited stations are spoiling the data.

“The best stations get adjusted up to the level of the worst stations,” Watts told FoxNews.com. “It’s like making a temperature smoothie. You put all these different fruits in to represent different qualities of stations and you run it through a blender and you get a milk shake.”

That problem of poorly sited stations thanks to “encroaching urbanity” -- locations near asphalt, air conditioning and airports -- is well established. A sensor in Marysville, Calif., sits in a parking lot at a fire station next to an air conditioner exhaust and a cell tower. One in Redding, Calif., is housed in a box that also contains a halogen light bulb, which could emit warmth directly onto the gauge.

Watts cherry-picked the well-sited stations and reanalyzed their data; his results show the planet warming at just 0.155 degrees Celsius per decade, rather than the 0.309 C per decade cited by the government.

[pullquote]

“I believe global warming is real. No doubt about it. Not a bit of doubt,” Watts told FoxNews.com. “However, I don’t think it’s catastrophic, or as bad as it’s been portrayed.”

Skeptic-turned-believer Richard Muller -- a University of California-Berkeley professor -- posted a new study online Saturday with equally sweeping conclusions. Muller’s Berkeley Earth Surface Temperature (BEST) study also say the planet is warming -- and concludes it’s solely because of man’s actions.

On the basic fact of warming, the two men seem to agree. On the details? Not so much.

“Last year, following an intensive research effort involving a dozen scientists, I concluded that global warming was real,” Mueller announced via an op-ed in the New York Times. “Humans are almost entirely the cause,” he wrote.

Muller’s study analyzed 250 years of temperature records. It concludes that the rise in average world land temperature is approximately 1.5 degrees C in the past 250 years and about 0.9 degrees in the past 50 years, a far steeper rate of change than Watts cites.

“Solar activity was not a major contributor, but there was a match to carbon dioxide,” he told FoxNews.com.

Muller’s team has completely re-analyzed the data from the surface station network. His analysis highlights several cold snaps that coincide directly with volcanic activity, further proof that his study is accurate, he said.

“I never imagined we would see [volcanoes] so clearly,” he said. “The fact that we can go back to the 1700s and see it so clearly gives us added confidence” in the temperature record.

Neither study is peer reviewed yet. Both men argue that by their work online prior to publication in a peer-reviewed journal, the discussion on the data can be broadened and made public.

Many skeptics take issue with what they call systemic data manipulation hidden from their view. For example, climate blogger Steve Goddard told FoxNews.com that “adjustments” made in the past to climate data have merely conflated the problem Watts uncovered.

“They started making what they called corrections after the year 2000, which turned the U.S. temperature trend from completely flat to fairly steep warming. That's what Anthony was questioning. The corrections were changing the temperature record,” Goddard said.

Several large adjustments hadn’t been documented at all, boosting readings by as much as 1.5 degrees over older measurements.

“It’s hard to tell exactly what they’re doing at this point,” he said.

Muller’s study attempts to correct for the quality of the data, in a transparent, repeatable fashion scientists should appreciate. Much of that data should be simply thrown out, Watts said.

“This affects the raw data, and there is no adjustment procedure in place to fix this,” he said. “BEST tries to solve it, and I applaud them for the attempt. But without knowing the history of the station, even their methodology doesn’t deal with it,” he told FoxNews.com.

There’s no “hockey stick” shape in Muller’s new graph, though it does ape that shape. But noted Penn State climate scientist Michael Mann said he agreed with it anyway.

“[It] demonstrates what scientists have known with some degree of confidence for nearly two decades: that the globe is indeed warming, and that this warming can only be explained by human-caused increases in greenhouse gas concentrations,” Mann wrote on his Facebook page.

Indeed, both studies conclude that the planet is warming. But the degree and cause of that warming remains a volatile issue.

“I think we would like to at least settle the scientific issues so we can move on to the more continuous political issues,” Muller told FoxNews.com.