Here is a link to a BBC report by Richard Black ( BBC Environment Correspondent) covering the recent issue of the IPCC final assessment on its 2007 report on the state of the environment.
Here are his concluding comments:
This is the IPCC's fourth major assessment of global climate change since its formation nearly 20 years ago.
During the course of its existence, it has become more certain that modern-day climate change is real and principally due to human activities; it has also become firmer about the scale of the impacts.
"If you look at the overall picture of impacts, both those occurring now and those projected for the future, they appear to be both larger and appearing earlier than we thought [in our 2001 report]," Martin Parry, co-chair of the impacts working group, told BBC News.
"Some of the changes that we previously projected for around 2020 or 2030 are occurring now, such as the Arctic melt and shifts in the locations of various species."
There are indications that projected increases in droughts are also happening earlier than expected, he said, though that was less certain.
The IPCC considered about 29,000 pieces of real-world evidence in compiling this report, as well as the projections of computer models.
These include observations showing that dry areas of the world such as the Sahel and southern Africa are receiving less rainfall, while it has increased in northern Europe and parts of the Americas.
The panel suggests societies need to adapt to future impacts, as well as curbing emissions.
Without extra measures, carbon dioxide emissions will continue to rise; they are already growing faster than a decade ago, partly because of increasing use of coal.
The IPCC's economic analyses say that trend can be reversed at reasonable cost. Indeed, it says, there is "much evidence that mitigation actions can result in near-term co-benefits (e.g. improved health due to reduced air pollution)" that may offset costs.
The panel's scientists say the reversal needs to come within a decade or so if the worst effects of global warming are to be avoided.
The findings will feed into the Bali talks on the UN climate convention and the Kyoto Protocol which open on 3 December.