The obvious issue is providing clean drinking water and sanitation to every single human being on earth at the cost of little more than one year of the Kyoto treaty.
Of course, the world is full of problems. But on the other hand it's important to get the sense... are we generally moving in the right direction or the wrong direction?
We need to invest dramatically in green energy, making solar panels so cheap that everybody wants them. Nobody wanted to buy a computer in 1950, but once they got cheap, everyone bought them.
To some, a cap-and-trade system might sound like a neat approach where the market sorts everything out. But in fact, in some ways it is worse than a tax. With a tax, the costs are obvious. With a cap-and-trade system, the costs are hidden and shifted around. For that reason, many politicians tend to like it. But that is dangerous.
When a business group tells us there is nothing wrong with the environment, naturally they may have good arguments, but we are also sceptical, because we know that they have an interest in these things.
The saddest fact of climate change - and the chief reason we should be concerned about finding a proper response - is that the countries it will hit hardest are already among the poorest and most long-suffering.
