Why are scientists concerned about an increase in the amount of carbon dioxide in the atmosphere?

Carbon dioxide in the atmosphere is not a concern as long as the amount remains fairly constant, so that it helps sustain life and maintain our temperatue at a comfortable level, suitable for human existence. Because carbon dioxide is a greenhouse gas, the present rapid rise in its atmospheric concentration is a concern because it is leading to global warming and climate change.

A warmer world might even sound desirable, but the long-term global trend to higher average temperatures poses a real risk to our economic and social well-being, as well as to the native creatures with which we share the planet.

Climate change is causing sea levels to rise. Not by much so far, but this is only the start. Higher sea levels, combined with the greater storm surges associated with climate change, will force people to abandon some prestige coastal properties. The inundation of New Orleans should have been a wake-up call, but many see this as a special case with no relevance elsewhere. Rich agricultural coastal flood plains will become salinated and unproductive.

Floods will become more frequent and more severe in some areas, while droughts will similarly become more frequent and more severe in others. Analysis of hurricane activity shows that severe hurricanes are becoming more frequent and more destructive, as a result of increased atmospheric thermal energy. Frequent storm damage to properties will cause insurance premiums to rise until some can no longer even afford to insure their houses.

Wildlife will suffer from loss of appropriate habitat and from heat stress. Some corals will die back as sea levels rise and they no longer receive sufficient sunlight, while others will be bleached by the rising temperatures and acidity.