h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

In this post-modern age I think it's tempting to seek the comfortable middle ground of "nobody really knows for sure..." Which may be fine when you're discussing art or whether love is real or a fictional invention, but when it comes to science it doesn't cut it.

The scientific evidence as of the year 2000 overwhelmingly supports the belief that the emmission of greenhouse gasses, primarily carbon diaoxide, carbon monoxide, and methane, caused by industrial pollution, transprtation pollution, and industrial scale farming, are the primary cause of global warming. There is almost zero contention of this opinion by any responsible scientist without vested interests. Statements to this effect have been published by every recognized group representing climatological and meterological expertise. That people and even responsible news organizations continue to suggest that there is a valid competing opinion reflects the fact that hardly anyone has the education to judge scientific data as well as the continued denial of industry, particularly the coal, petroleum, power, and automibile industries, in the face of overwhelming evidence.

The nature of this evidence, incidentally, are incredibly advanced computer modelling techniques which allow us to build models of climate and then predict how various inputs affect them. Scientists have tested the validity of these models by examining real world scenarios of greenhouse gas emmissions - from volcanoes, for example - and comparing the models' predictions to what actually happens. The accuracy of the results of these experiments have put the doubts of unbiased naysayers to rest. For the accuracy of these models to be a coincidence would be a breach of probability that would lead one to believe that the Heart of Gold was in the vicinity.

If you want to know the real story, go to serious scientific publications like Science, Nature, or the American Chemical Society's Chemical and Engineering News. The latter is particularly valuable, as the ACS is heavily invested in the petroleum industry and there is no benefit in their subscribing to the greenhouse gas theory of global warming. Yet they do support that theory, for a simple reason: it is the theory best supported by the best scientific evidence.

This being said, there are still a lot of unanswered questions. How will weather patterns change? how high will sea levels rise? Are catastrophic weather events being caused or made worse by global warming? But the basic premise that human production of greenhouse gasses is a key root cause of global warming no longer needs to be defended. It's as close to fact as science gets.

Incidentally, I have a bachelor's degree in chemistry and have worked professioinally as a researcher on pollution issues. I'm not an expert on the climate but I think I am justified in representing the tide of opinion as represented in the scientific press.

So why can't the models accurately predict what will happen if the Earth does get warmer.

Models are only as good as the people who program them, and of course any assumptions (and you must make assumptions) made in a model can affect the results.

I'm an astronomer. Look at the tooth-and-nail fight over the Hubble Constant, and you can see just how easy it is to get different results from the same data. You can also see how far a "reputable scientist" will go to make a data set produce their result.

We are still emerging from an ice age. The place where I sit at this moment ( Alberta, Canada) was covered by a ice a mile deep a mere 14,000 years ago. If (unsteady) warming had not been occurring for that long humans would not occupy America, but we would be able to walk from Bejing to Jakarta, given proper footwear and time off work.
This is the fifth warming trend in the current freeze. The first four faltered and the ice re-established itself. I do hope the tropical norm is finally restored, but in any case there is no such thing as a static 'balance' to be disturbed, or not, by human activity. Shutting down the industrial engine that feeds billions would not even stop the warming let alone restore an Eden that has never existed.
Of more interest is the question of where we are going to put billions of displaced coastal dwellers and how will we stop them from killing each other as they compete for new ground.