An update to the most recent IPCC [Intergovernmental Panel on Climate Change] report warns that even smaller temperature increases could mean even larger real life changes than earlier IPCC projections. This study was authored by a panel of scientists whoare members of the IPCC. Apparently the IPCC formal report was watered down bit to please a broad spectrum of members. The study, published in the Proceedings of the National Academy of Sciences, is titled "Assessing Dangerous Climate Change Through an Update of the IPCC 'Reasons for Concern."
This new report lists five areas of major concern: 1) We may see the entinction of indigenous tribes, animals and sensitive ecosystems--coral reefs, tropical glaciers, endangered species, unique ecosystems, biodiversity hotspots, small island states.
2)More extreme weather events: Hurricane Katrina, 2003 heat wave in Europe.
3)Low altitude places (Bangladesh, Miami, Venice) and impoverished areas under more stress and greater threat.
4)Global impact can affect hundfreds of millions of people, disrupting eocnomic, political and agricultural systems.
5)Tipping Points in numerous natural processes. E.g., there's now better understanding that the risk of additional contributions to sea level rise from melting of both the Greenland and possibly Antarctic ice sheets may be larger than projected. Several meters [3 meters = ten feet] of additional sea level rise could occur on century time scales.
Bottom line from these scientists: the more we learn about global warming, the more severe the threats that can be seen.