"For every complex problem there is an answer that is clear, simple, and wrong." H. L. Mencken

What caused the end of the "Little Ice Age" just a couple hundred years ago? It happened before the Industrial Revolution, so it seems unlikely that it was ended by human activities. If that's the case, then what's to say that the reported rise in global temperatures today is caused by human activities?

This topic has become nearly religious dogma with some, to the point that anyone who dares question it is ridiculed or labeled some sort of heritic. Dogma is for morons who are unable to think for themselves.

As for the computer models of the climate, they're still woefully inadequate for the task. I've spent 20 years programming computers, so I know what goes under the hood for models. The more accurately a physical system is understood, the better the model. The climate models are based on too many assumptions and too few data sources.

As stated here:

Science is to be preferred over fiction. The current generation of climate models, no matter how noble, fails to comprehend the difficult conditions of THC's past or future states -- strengthening, weakening or collapsing. Touting greenhouse gas emission reduction to save the world from a future glacial period is an unqualified prescription with no scientific vetting.

As for the scientists themselves, Let Them Confess Their Faith:

It wasn't long after I became a research scientist that I learned that scientists aren't the unbiased, impartial seekers of truth I always thought they were. Scientists have their own agendas, philosophies, pre-conceived notions, and pet theories. These views end up influencing their science. Nowhere does this have a greater impact on the science than in global warming theory.

When confronted with a new, policy-relevant science problem, there are always scientists that will immediately rush to judgment about a "possible" environmental catastrophe. In the 1970's it was an impending ice age. In the late 1980's it was inflated global warming predictions. Most recently both extremes have morphed into the possibility that global warming will actually cause an ice age for Europe. In an age when popular culture helps to blur the line between science fiction and reality, our imaginations are fired by the thought of an ice sheet advancing on a city, or unexplained increases in severe weather.

On February 4 I testified in a congressional hearing that was held to explore the role that science plays in public policy formulation. I tried to explain that science always involves assumptions, and so scientific conclusions are only valid if the assumptions hold up. And there are always additional, unstated assumptions that the scientist isn't even aware of!

For a complex problem like climate change, assumptions abound. Early in the climate modeling days, confidence was high as physicists used to working on well-defined problems with a limited number of variables thought they had the answer. We meteorologists (by training) were always more skeptical because we understood how complex weather is. Enter the scientist "heavy hitters" that are savvy public speakers, maybe a Nobel laureate in some unrelated field of science, all having strong opinions about what the government should be doing to help "save the Earth" and you have a recipe for bad policy. Now, the climate modelers are learning how complex the climate system really is (surprise!). The tendency for scientists to rush to judgment isn't the fault of science -- it's just human nature.