Short answers, pulled from the story.
The IPCC Fourth Assessment Report, titled Climate Change 2007, was published in 2007 by the United Nations Intergovernmental Panel on Climate Change. It is the fourth in a series of reports assessing scientific, technical, and socio-economic information on climate change, its effects, and options for adaptation and mitigation. It took six years to produce and cited over 6,000 peer-reviewed scientific studies.
The IPCC Fourth Assessment Report involved more than 450 lead authors, more than 800 contributing authors, and more than 2,500 scientific expert reviewers. People from over 130 countries contributed to the report.
AR4 projected a best-estimate surface air warming of 1.8 degrees Celsius under the most optimistic scenario and 4.0 degrees Celsius under the most pessimistic scenario by 2090-2099, relative to 1980-1999 temperatures. Even if greenhouse gas concentrations had been frozen at year 2000 levels, a rise of about 0.1 degrees Celsius per decade was still expected for the following two decades.
Working Group III estimated that stabilizing greenhouse gas concentrations at 445 to 535 parts per million would reduce average annual GDP growth rates by less than 0.12 percent. A substantial fraction of those costs could be offset by health benefits from reduced air pollution, improved energy security, and increased agricultural production.
A paragraph in the Working Group II report projected that Himalayan glaciers could disappear by 2035. The IPCC later acknowledged the date was incorrect, tracing the error through a misquotation chain from an ICSI report through a WWF report. The IPCC maintained that the summary-level conclusion about Himalayan glacier recession remained robust.
The Synthesis Report concluded that warming of the climate system was unequivocal, that most warming over the prior 50 years was very likely due to human activities, and that impacts would very likely increase with more frequent and intense extreme weather events. It also found that anthropogenic warming and sea level rise would continue for centuries even if greenhouse gas concentrations were stabilized, and that unmitigated climate change would likely exceed the capacity of natural and human systems to adapt.