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Originally Posted by Richard
Why is a warmer world a worse world?
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Because of it's lessser ability to support the life that is not extinct today.
It terms of the effect on humans the downside is increased malaria, dengue fever, increased CVD, and malnutrition, increased water stress decreased arable land, displacement of people in many areas, increased floods and droughts, increased storm incidence and intensity, and the cost to the economy of changing land use that is no longer suitable for its current use.
Current human mortality attributable to climate change is about 150,000 people per year. (see: Impact of regional climate change on human health,
Patz et. al. Nature 2005)
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The Earth has been warmer than it currently is many times in the past and there's never been a suggestion that this causes a catastrophe.
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Only a very long time ago. Only a very few living fossils alive today have survived a world that is detectably warmer than it is currently.
Note also the speed of this warming is unprecedented except where it has been a catastrophe. Plant migration takes time. Of course these days there are physical land use barriers to plant migration as well, which is why estimates of the extinction rates of the world's species are up around 25% of all species (See: Extinction risk from climate change,
Thomas et. al. Nature, 2004), with worst case scenarios over 50%. (Note that current emissions are
worse than the worst case scenario.)
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In fact warmth is essential to most life, perhaps a warmer world will actually be a generally better one?
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Life adapts to it's environment over millions of years. If that environment is changed over hundreds of years, extinctions result.
But the the weather itself becomes more dangerous in a warmer world, and we haven't even touched the effects of a higher CO2 atmosphere alone, which means lower plant transpiration threatening the worlds rainforests, particularly the Amazon whose West is entirely dependent on transpiration for rainfall, the acidification of the oceans which threatens oceanic calcifying organisms - a very important CO2 sink, as well as the obvious disaster to the oceanic food web if they go extinct, and a reduction in the nutritional value of plants.