Chickenman, a few quick replies.

Volcanoes (and any other large source)- yes they can put out huge amounts of greenhouse gases due to *natural processes*. These processes are part of the natural system, and is fine. The issue becomes pulling out trillions of tons of carbon (fossil fuels) that have been stored underground for millions of years. This Carbo has not been part of the natural system, and to pull out those billions of tons of carbon and put it into the active atmosphere and biosphere in the matter of 100 years is a very strong shock to the system. The changes in greenhouse gas concentration of this magnitude typical occurs over thousands to millions of years.

The earth's climate has changed before- simple and short answer to this- yes it has. But never at this rate, which is very important. Most species, including some aspects of human society, are not able to react and deal with changes in climate at that speed. Absolute best example, coastal communities. We've already seen sea level rise and it's on going to go higher due to climate change. The majority of the world's population lives on the coasts, sometimes withing feet of elevation of the water. Sea level rise is going to be very costly to deal with, no matter how you slice it.



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