The science in the IPCC (International Panel on Climate Change) report is contained in the report published by Working Group 1 of the IPCC, the UN’s Intergovernmental Panel on Climate Change. I suspect that few people have actually read this ~1500 page tome. Most people read the Summary for Policy Makers, which is written by bureaucrats and does not, in my opinion, faithfully reflect the contents of the actual report. There is too much emphasis on worst-case scenarios, which the report does not say are the most likely ones, in the Summary.
As best I can make out, what the report itself says is this: Global warming isn’t likely to be a big deal. It is unlikely to cause significant harm over the next 100 years or so. In a followup special IPCC report even in the worst-case scenario the prediction is a fall in economic productivity of 10% of what it would otherwise be by 2100. That’s not even noticeable considering the growth in the economy that will have occurred by then.More