It's Really, Really Unlikely that Climate Change is "Naturally Occurring"
This is probably the most commonly offered rejoinder to the scientifically observed phenomenon of global climate change. Well, sure, temperatures are rising around the world, and last decade was determined by NASA, NOAA, and a number of the world's other top tier scientific institutions to be the hottest ever. But how do we know it's man's fault? Couldn't it be a natural process, like sun spots, or a naturally-occurring increase of cloud cover or something, that's causing the warming of the world? The short answer is: Nope. Or rather, at this point, it's very, very unlikely. Put very simply, the basic reason for this is that there is a large body of evidence that strongly supports the theory that man-made greenhouse gases are the culprit in warming the climate. But there's no other coherent theory yet proposed that successfully explains all that evidence -- indisputably rising temperatures, increased CO2 concentration in both the atmosphere and oceans, and so forth.
In other words, there might be another explanation that could somehow explain all of that stuff better than the fact that there's an increased concentration of man-made greenhouse gases in the atmosphere that just hasn't been discovered yet. But the puzzle pieces of the anthropogenic theory just fit together too cleanly -- it's by far the best theory yet proposed, and even skeptical scientists might agree with that.
Now, there are a couple high-profile scientists that support the "naturally occurring" theory (not-so-coincidentally, these scientists mostly enjoy their high profiles for doing exactly that), most notably MIT's Richard Lindzen and Roy Spencer. These scientists are among among an extreme minority amongst the climate science community, largely because their arguments seem implausible.
Skeptical Science relays Spencer's most recent misgivings with the scientific community:
"Spencer has grown frustrated with the fact that most of his climate scientist colleagues conduct research under the premise that the recent warming is anthropogenic, and in an article on his blog, has thrown down the gauntlet: 'Show me one peer-reviewed paper that has ruled out natural, internal climate cycles as the cause of most of the recent warming in the thermometer record.'Skeptical Science's Dana Nuccitelli then proceeds to kindly explain that nobody has ruled out anything -- and pointing out that there have been no peer-reviewed papers ruling out leprechauns as the cause of most of the recent global warming, either. But that doesn't give us an excuse to ignore the mounting evidence that supports the theory that humans are causing climate change. And at this point, that evidence is so compelling that it's difficult to see the merit in holding out for some alternate theory -- as nice as it would be to discover that humans aren't the root cause of warming up the planet, and that we don't have to change our industrial habits after all.