If the permafrost melts, think of all the new arable land that will be available for farming. Think of all the species that will be able to expand their populations into. Think of all the grasses that will "eat" the CO2.
Let's talk about benefits from warming. Climate change has winners as well as losers. History has shown that there are more winners than losers as the world has gotten warmer. Life is more abundant today than any time in the past since the last ice age for most species including man. A couple of extra degrees will make it even better. Sure, it may negatively affect 150 million people who live a low areas by the sea. By there's billions more that warmer weather will make it better for.
Think of all those cold Canadians who won;t have to flee to FLorida in the winter.
Alan, we had this discussion before. The sudden and unpredictable temperature swings are a big problem. As shown somewhere else on the first few pages of this thread, 2 degrees higher temperatures killed thousands of people in Asia and Europe in the recent summers.
This year, in Ontario we had 15 record warm days. That's as of 15th of January. We haven't been able to skate outdoors yet, but more slush and ice the ice had been forming on the sidewalks than usual. The warm winter days ruin also all the fun and fish harvesting from the winter ice fishing. Most fishing huts are still sitting in the suburban driveways and backyards. Not speaking about ruined skiing season.
The changing weather patterns are also a problem for the snow birds. In southern Florida, the second half of December was the coldest, windiest and wettest 2 week period in the recent history. With huge and angry waves preventing swimming in the ocean.
The greatest benefactors of warmest weather in the northern hemisphere are all kinds of insects. Personally, I saw in Ontario a great increase in japanese beetles, mosquitoes, and ticks. The onslaught of japanese beetles destroyed many berry bushes in matter of days and the hordes of mosquitoes ruin all fun from carrying a canoe just from the parking lot to the lake. The problem with destroyed berry bushes is not only that one summer harvest, but a setback for the entire plant. Two seasons in a row like that, and the mature and nice bushes are finished.