Make it profitable to be clean, or force them to be clean by government action, and the problem will resolve itself in your country.
If other countries are polluting, stop trading with them if you can or tax them heavily and invest the tax money into environmental pursuits.
In short, this is an economic problem. Governments, and even individuals, can vote with their wallets to improve the situation.
The vast majority of people are greedy, uneducated and selfish.
Fix that and you won't just fix climate change you'll fix a lot of our issues.
That's a naive view of human personality. The reality is that all people are "greedy" and "selfish" in that they consciously or subconsciously pursue their own interest. (Some people do suffer from various degrees of developmental trauma that affects their ability to do that easily, but the part of the brain that is responsible for that still exists. "psychologists" sometimes refer to this as inability to perceive borders, perception of self etc).
Now, the set of people that you are referring to by exclusion, i.e. those that are not "greedy, uneducated and selfish" simply find themselves in a priviledged position and signal virtue by painting themselves as climate conscious individuals. Of course, the brain hides most of the real motivation behind this reasoning.
Are there also people who want to see the world burn? Absolutely. Again trauma does that to people. But most mentally "healthy" people don't want the planet to become uninhabitable for human life.
This is all coming from someone who was at one point in life deeply affected by intense destruction of natural ecosystems around, intense logging, illegal deforestation. I was an avid cyclist and used to love nature and was seeing the destruction on my rides. But you learn to accept that, this is the way of life.
Now, to answer to original question. What must happen for humanity to coordinate on solving this problem? I don't expect humanity to be able to do it. But I think what would need to happen as a stepping stone, is to end most of the conflict in the world right now. This is of course impossible to do in one generation. When you stop seeing the world in "us vs them" and the vast majority of people emphatize with everyone else and other life forms, i think coordination is possible. I doubt humanity will reach that point though.
With respect to our closest relatives, it is interesting that our level of aggression is in the middle of the chimps and bonobo's. Apparently, we are at the right level between individualism and cooperation to have developed the kind of intelligence we posses. If we would have been more cooperative, and value our personal interests less than that of the species, we would not have developed the technology that we now cannot handle. That we are a species that can use language to create intrinsic lies, is also not helping. On one hand language has helped us to cooperate without submitting to the whole, but also has lead to the development of politics: leaders who can convince others that they are good leaders based on what they say.
(Yes, this means we’ll wait a long time before acting.)
An even hotter summer heatwave causing large numbers of deaths in continental cities should make politicians take much closer notice.
Although it doesn't please me to say this, I think this is the crisis we need in order for this problem to start being taken much more seriously. Change can happen in a crisis.
For that matter, the climate-change-is-a-hoax politicians are doing equally well with COVID19-is-a-hoax.
That applies to only half the population in one country with about 4% of the world's population, but it's responsible for 25% of the greenhouse gas emissions (and 20% of the COVID19 deaths). The new data may nudge enough of them to cause a significant change in the outcome if an election, but it would at best be temporary since so many other things can nudge it back come the next election.
I don't see anybody taking climate change seriously who isn't already. It's just too effective as a political strategy.
Otherwise I think the impacts of events from climate change must be more pronounced before we see more focused action.
A co2 tax disallows companies to externalize the damage to the environment. Hoping for innovative forms of energy production and storage. We have some of that already, but the investment costs are too high.
Resource consumption is the root of all environmental impact. High populations tend to exacerbate that impact to the point where it is negative. So once the population reaches a certain level, even a minimal existence creates a negative impact.
Good luck convincing even a majority of the population to reduce offspring (capitalism as we know it requires population growth), reduce consumption (people are greedy and wasteful), and change their lifestyle (from eliminating chemical products, adopting a zero trash lifestyle, to giving up cars, yes even the electric ones). Then you'd have to get countries to work together not just to essentially ban greenhouse emissions, but also reverse the warming trend by blocking solar energy in space or the atmosphere and recapturing greenhouse gasses, etc.
It's gonna be tough or impossible.
Consider the models that were used in the first days of the COVID pandemic to predict the trajectory of deaths over time by US State. It wasn’t that they were wrong...that was to be expected. What was problematic was their estimates of the uncertainty in their estimates of those trajectories which, if I remember, was way too small. You will overinvest if the uncertainties are understated...and the very modelers who understated the uncertainties will be first line to sop up the money. Convenient.
The loudest voices, whether politicians or scientists, will generally overestimate how much confidence we should place in their predictions. “The seersucker principle - for every seer, there’s a sucker.” Especially when there is a 10 Trillion Dollar international slush fund waiting to be established and milked. That’s a lot of graduate stipends, and somebody has to eat all those Viennese pastries at international conferences.
Well, what about consensus? You mean a Mongolian cluster...umm...let’s just say that there is no way to quantify the reduction in uncertainty when a group of experts, who stand to gain reputationally (for at least as long as it takes for their kids to get out of college), say that something is a sure thing. I believe that a relevant phrase from finance is “lipstick on a pig”.
But we have to do something, right? Well, are there lower risk investments? Well, a lot of folks are going to die in China, India and the like from air quality, if certain health models are correct. Models that can be verified a lot more easily than global climate models. India needs technologies to plant crops without burning fields. Those are well-established technologies that could be implemented in India today with a small fraction of just 1 Trillion. Scrubbers on coal plants in China? Direct lives saved this decade. Electric vehicles? A win-win according to some analysts for both short term and, if the climate models are correct, long term. Nuclear power? Replacing burning wood with cleaner household fuels? Let’s address deforestation too.
What about climate modelers? We still need researchers and research...because we live here. On Earth. Nice to know where the light switches are, for a lot of good reasons.