If the Earth really did warm up ten degrees, we'd double the sustainable population in return for a few swamps and sandbars being under water. When you turn a ten week growing season into a twenty week growing season, you take a climate from barely livable to really bloody useful.
Wow, where are you pulling this from? Firstly, if the Earth warms up by 10 degrees (celsius? fahrenheit? either way 10 degrees is a crapload) the amount of dry land would dramatically decrease due to rising sea levels. All coastal cities would be flooded without massive man-made structures to keep the water at bay (the cost of which would be impossibly high except for the wealthiest cities of the wealthiest nations).
Raising global temperatures by 10 degrees would also in no way increase the growing season - it would in fact do the opposite (for the most part, though there would be exceptions). It would turn most currently arable land into desert, but the bigger problem is that it would dry up most of the fresh water on the planet. No matter how much arable land you have (and all models predict that a dramatic increase in temperature would drastically reduce it), you aren't going to grow jack without fresh water. Not to mention that water shortages are already a problem in the dryer parts of the world, such as in parts of African and the Middle East.
Another problem associated with such a big increase in temperatures is that insect-born diseases (the most prominent one probably being malaria) would become much more widespread. Say good-bye to Africa!
The Earth is, for several years in a row now, cooling off. Being stupid and educated just makes a moron more dangerous to himself and others.
Someone else already pointed out that a trend of 'several years' is meaningless regarding geological and climatologic timeframes. The temperature has been cooling down for the past several years but it doesn't change the fact that over the past century there has been a clear trend of increasing temperatures. Now it is possible that it's all part of the natural cycle of the Earth's climate. But like it or not, for the past century humanity has been pouring all sorts of pollutants into the atmosphere and cutting down forests at extraordinarily high rates. So high in fact that we can actually measure significant changes in the levels of many chemicals, including CO2, methane, CFCs, and a whole lot more.
Chemicals like CFCs are artificial - they do not exist in nature unless we put it there. And yet, during the last century (less, even, they were invented in 1928 and were largely banned worldwide in 1994) we dumped so much into the atmosphere that we affected a noticeable decrease in ozone levels in exactly the places where most light-weight molecules are expected to end up (due to winds and the rotation of the earth). The fact is that we have affected the atmosphere by spewing chemicals into the air before; and the amount of CO2 emissions we've produced since the Industrial Revolution exceed those of any other chemical ever by leaps and bounds. And it just so happens that over the last century global temperatures have been rising faster than expected.
Arguing that us puny humans are incapable of affecting the Earth's climate are downright ignorant. We know we've affected the planet in significant ways (we've messed with the ozone layers, polluted pretty much all of the water on the planet and destroyed vast swaths of forests; we've converted millions of square miles of plains and other terrain into farmland, diverted rivers, build and blown up islands; we've even managed to light up the dark side of the earth! And most of these were small-scale achievements, made by single nations or even smaller groups; emitting pollution is one of the few things all nations have happily contributed to).
So we can chalk it up to coincidental simultaneity of the onset of the industrial revolution and the accelerated heating up of the planet - which so far has never been convincingly explained via natural phenomena. Or, we can take a hint, err on the side of caution and do what we can to mitigate the consequences of our carelessness. If we do our best to stop or reverse the effects of global climate change, and it turns out that it was never our fault to begin with and our actions achieve nothing, then all we've done is waste some time and effort (if you can call developing alternative energy and more energy efficient products a waste of time). But if we do nothing and it turns out that we really are responsible for the changing climate, and it really is as bad as a whole lot of researchers in the field believe, then we should all be arrested for negligent endangerment of generations of children.
We know that the climate is changing. It's already been shown pretty effectively (thank you Mumblefratz) that it's exceedingly difficult to find anyone qualified and without conflicts-of-interest arguing that the climate isn't changing. And there is clear evidence that we might be responsible for that change. There's a chance we aren't responsible for it, but IMO enough qualified people have run warning bells all over the world that it warrants serious consideration.
From the research I have done (and I have done considerable research into the topic and have had the opportunity to speak one-on-one with physicists and climatologists who have made this the research topic of their lives), I am convinced that there is a good chance that the effects will not only be undesirable, but catastrophic.
Based on the fact that the climate is changing and my opinion that the chances of disastrous consequences are high, I'd much rather we play it safe and do what we can to at the very least mitigate the damage. I mean, take the following example: the chances of you dying in a car crash whenever you pull out of your driveway are extraordinarily small. But I'm willing to bet that the vast majority of you buckle your seatbelts nearly everytime, anyways; because if you do get into an accident that seatbelt might just save your life. In this case, climate change is the accident that might happen (and I think the chances are higher than a car crash), and combating climate change via whatever means is your seatbelt. Except in this case, it's one big seatbelt for everybody on the planet including future generations. If not enough people are willing to bother with the mild inconvenience of helping to fasten that seatbelt and that car crash does happen, then everybody loses. On the other hand if everyone contributes, and the crash happens, we have a good chance of getting up and walking away from it unharmed. And even if it doesn't, all we've lost is the little bit of time and effort we contributed - much of which will have yielded useful advances anyways.