The ecosystems provide us with about $30 billion from natural processes, such as pollination, water purification,etc. All of the world's economies add up to less than $20 billion. In addition, there are so many jobs that can be created out of this field, such as environmental engineers and designers of new eco-friendly technologies. These far outweigh the arguments against.
Climate change is a serious problem that needs to be addressed. The government should do what it can to limit the dangerous effects that are being produced. The longer the delay in implementing a good policy the more problems that are likely to occur on this planet. Action needs to be taken now.
The US should do more on climate change for several reasons. Since this question addresses only the economy, I'll speak from that perspective.
We are lacking jobs. We have many skilled people who are unable to find work, who could be put to work making our country (and world) a better place to be. Green energy projects are both good for the environment, and good for making money. These projects will save our planet, save us all money (goodbye fossil fuels), make us energy independent, and, most of all, put money in regular folks' pockets. Those people will then be able to put that money into the economy again, thus strengthening it.
Climate change is largely adopted from the liberal media and those who, for social political reasons, want to slow down the economy. The will of these believers is to increase social welfare programs making more people dependent on the government and therefore giving more power to control the population of the U.S. to the will of our lawmakers.
The government intervening to increase the amount of spending on green technologies would not help the economy, but rather the opposite. This is because,, even if we accept Keynesian economics, the multiplier from investing in green technology would be so small (due to virtually no short term AD boosts and tech gains) in the short run it would only have an inflationary effect on the economy.