The IPCC's latest report does NOT state that the science supporting global climate change is "weaker than ever".
That's a pretty abusive characterization of the latest report. The most important climate variable, the temperature forcing sensitivity of CO2 concentration in atmosphere was loosened to a factor of three difference between highest and lowest estimate. It's now back to where it was in the late 19th century with Arrhenius's estimates (which I gather is the basis for Jane Q. Public's claim that the science is "weaker than ever"). Extreme weather was put on the back burner. We're left with a greatly weakened case for urgency as a result. Those are huge changes.
Sure, a few minor botches were discovered in the report, but that doesn't change the fact that there is some evidence, supported by the opinions of a large though undetermined majority of climate scientists (most who don't have any more experience or knowledge than knowledgeable outsiders), that global warming is real and partly caused by human actions.
FIFY. Note both the weakness of the actual claim made and that it doesn't actually translate into a call for action. Just because a narrow category of scientist, most which don't actually do research on global warming, happen to have an opinion that there is some degree of human-induced global warming doesn't mean that we need to act to reduce CO2 emissions.
And I question whether there actually is that high a level of agreement. From this story, we have the following comment on a 2007 survey:
Of the 489 Earth and atmospheric scientists surveyed by Harris Interactive, 97 percent said that global temperatures have increased during the past 100 years, and 74 percent agreed that "currently available scientific evidence substantiates the occurrence of human-induced greenhouse warming." The findings mark a significant increase in concern over climate change since 1991, when a Gallup survey of the same universe of scientists showed only 60 percent agreed that temperatures were up and 41 percent believed that evidence pointed to human activity as the cause.
74% is a fair bit short of your "over 90%" claim, but that includes scientists without a direct financial or status stake in global warming being true. Now there's been a few years since 2007, but I see no evidence, despite widespread government bribery, that the evidence has improved significantly. To the contrary, the IPCC had to weaken their case as Jane Q. Public noted.