For good God's sake, one of the first damn principles in science and philosophy that I learned was that correlation does not equal causation. Similarly, the Romans recognized the error of thinking post hoc, ergo propter hoc (after this, therefore because of this).
And yet, so many scientists claim that the cause of global warming (which is, I admit, apparently undeniable--at least in the short term) is the result of increased carbon gas emissions since the advent of the industrial revolution (c. late 1700's). However, logic tells us clearly that just because these two things correlate (somewhat--check the freaking records!), neither can be construed as the cause of the other, for it is equally probable that they are either both results of an altogether different cause (which, makes no sense at all--that a warming climate led to an increased burning of fossil fuels is quite absurd) or completely unrelated (very likely, but not very dramatic).
Ockham's Razor--a basic principle in so-called "modern science" (I use quotation marks because the idea is about 700 years old)--tells us to look to lex parsimoniae (the law of parsimony/succinctness). Simply put, nearly one thousand years ago, William of Ockham pointed out that entia non sunt multiplicanda praeter necessitatem (entities should not be multiplied beyond necessity). In layman's terms, this means that the most likely answer/cause is the answer/cause. Such reasoning is quite reasonable whenever solid, irrefutable evidence pointing toward a single answer/cause does not exist.
Knowing this, I ask you which is more likely:
That the climate has been steadily increasing since the Ice Age (thousands of years before the industrial revolution), and is therefore a natural occurrence, completely independent of human action; or that the Earth warmed naturally from the Ice Age but then stopped at some kind of arbitrary point and that human beings have managed to pushed the climate beyond that "naturally" arbitrary point?
Basically, it is irrefutable that the climate warmed thousands of years ago without human assistance. Those cavemen, while they might have been able to use Geico.com, produced as a whole over several millennia, fewer "greenhouse gasses" then I do after a trip to White Castle. So it is established that the Earth can warm on its own.
Considering Ockham's contribution, then, it is far more likely that the Earth is simply continuing what it started ten thousand years ago with only brief respites.
Let's not forget the motivation behind the Chicken Little's who cry that the sky is falling.
Some are politicians (e.g. Al Gore) who can use such fear to catapult themselves to the pinnacles of power. Many are egotists who are so pathetically lonely that they must use such fear to make themselves seem important. Still others have their eyes set on the money that keeps pouring in from ignorantly desperate governments who lack the wisdom to just say "No." Perhaps more insidious is the fact that many socialists who advocate a command economy have seized upon the issue in order to gain control over the modes of production and consumption.
But let us not forget that demagogues lead their people to Hell. Egotists care for no one but themselves. The greedy will do anything for money. And the socialists will sacrifice the lives of millions to see their collectivist schemes enacted. You don't believe me? Study the histories of the Stalinist Russia and Maoist China.
They tell us that it is likely that humans are causing global warming. However, with a complete lack of knowledge about what causes the climate to increase naturally, anything is a likely candidate. Imagine a room full of one thousand people. The room is dark. No one can see. A murder is committed. The lights return. Every person there is equally likely a suspect.
While the industrial revolution was underway in Great Britain and the United States, Ludwig von Beethoven composed his 9th Symphony, famous for its "Ode to Joy." Ever since it was first performed, it has been performed constantly. It correlates to the supposed advent of global warming.
Another factor that most people don't consider is that human beings could not come close to recording accurate temperatures until the early 1700's. Since the Earth has been around far longer than that, these so-called scientists are claiming that a mere 300 years (out of millions and millions of total years) is enough to establish supposedly "normal" climate patterns. You should not have to think long to see this as nonsensical. 300 years is not even one half of 1,000 years, and recorded history far exceeds 2,000 years. In a nutshell, 300 years is a completely insufficient sample. Add to this the fact that the climate has gradually warmed on its own since the Ice Age, and you can see even more problems with the "Sky is Falling" camp.
Still another point to consider is that whenever a major volcanic eruption occurs, the Earth (quite naturally) deposits far more "greenhouse gasses" into the atmosphere than man has ever produced in all of history. Check the data on Mount Pinatubo's 1991 eruption for actual evidence to this point.
If nature itself can outdo man's entire repertoire in a single volcanic eruption, who's the more likely culprit in global warming?
Remember, I'm not saying that overall temperatures have not increased since they've been recorded. What I'm saying is that there is no proof that humans have caused this increase, and that such a claim is baseless. Conjecture is not evidence. Possibility is not evidence. If it were, then every person in Dallas on November 22, 1963 could be a "likely" suspect in President Kennedy's assassination (for the record, it was Lee Harvey Oswald. Read Case Closed by Gerald Posner if you wish to disagree).