But you've hit on a problem: can we maintain global cooperative institutions in the face of an expansionist hegemonic power like China? I don't think we can, because anything controversial and it gets ripped apart.
The US and allied countries have their own national organizations, but even the EU is compromised on a number of issues, such as creeping fascism (Poland and Hungary) and the inability to take action against member states, or even coordinate in a pandemic. Even NATO is compromised by expansion to include such countries, and Turkey as well. So I'm questioning how useful large group multi-lateralism is for an organization like the WHO.
Edit: And I just scanned the last week of posts and can't see mention of anything like that. You're confusing with user koolba.
The accuracy of answers about the source of a virus was very much dependent on the level of openness and cooperation from the jurisdiction in which the virus originated. Climate change, on the other hand, does not have a single geographical source, and therefore the IPCC is less limited in the information available to it.
Similarly, I suspect that the WHO's early mistakes or inaccuracies in assessing the dangers of the virus were due to the fact that most of the early cases and mortality data were being collected in a single jurisdiction.