Undeveloped countries who then develop and start utilizing resource that produce pollutant emissions will keep increasing into the future. No matter how many cuts developed countries make, there will also be a large amount of emissions coming from countries who choose not to adopt any kind of restrictions on emissions of pollutants.
Green energy sources, which produce less bad effects for the environment and the climate, will eventually lead to lower energy costs. An example of this is solar energy, coming from the sun - an energy source requiring no management by humans. Because of this combating climate change will eventually lead to lower costs which could justify the costs to develop it.