As Autonomous Mind says, the IPCC isn't about science, but politics. A nicely mocking piece from the Telegraph -
"In a leaked June draft of the report's summary from policymakers, the IPCC said the rate of warming in 1998-2012 was about half the average rate since 1951. Several governments who fund the body have since complained about how the issue is tackled in the report. Germany called for the reference to the slowdown to be deleted, saying a time span of 10-15 years was misleading in the context of climate change, which is measured over decades and centuries. The US also urged the authors to include the "leading hypothesis" that the reduction in warming is linked to more heat being transferred to the deep ocean. Belgium objected to using 1998 as a starting year for any statistics. That year was exceptionally warm, so any graph showing global temperatures starting with 1998 looks flat, because most years since have been cooler. While Hungary worried the report would provide ammunition for sceptics."
I blogged about the vested interests which act as "scientific" advisors to this dodgy UN outfit back in January.