Critics of the report
Despite the breadth of the scientific expertise involved and the extensive review and approval process, the assessment reports spark quite a few criticisms, from both climate change believers and skeptics.
Skeptics say the panel exists only to produce further evidence supporting the idea of man-made climate change while ignoring opposing research. But climate change activists, and many climate scientists, say the panel's consensus-seeking policy produces conclusions and estimates that are too conservative.
Another often-cited critique of the report is that, due to its size and lengthy approval process, it is already outdated by the time it is released. Several important studies already have been published in the past year in the constantly evolving science of climate change that will not be included in this assessment.
Despite the critics, this week's document will serve as a major measuring stick for the current state of the world's climate and what type of change is in store.
The summary for policymakers will be available Friday at www.climatechange2013.org.