The way the author keeps framing this as a first step to accountability it's almost sorta cure, of it wasn't so dangerously naive. Frankly, in today's political climate, the idea that those responsible will see any form of consequences is patently absurd.
Climate
Discussion of climate, how it is changing, activism around that, the politics, and the energy systems change we need in order to stabilize things.
As a starting point, the burning of fossil fuels, and to a lesser extent deforestation and release of methane are responsible for the warming in recent decades:

How much each change to the atmosphere has warmed the world:

Recommended actions to cut greenhouse gas emissions in the near future:

Anti-science, inactivism, and unsupported conspiracy theories are not ok here.
They knew about the toxicity of lead also, but somehow it came as a shocker when they discovered spewing it out of millions of tailpipes was leading to an accumulation in the environment.
Of course they did. This is one of issues with our models of democracy, that may be quite difficult to solve.
Politicians and their parties have 4 or 5 years to introduce new and alter existing legislation, sign contracts with companies and agreements with other countries. If they don't do anything for 'now', and focus on the future - people won't vote for them anymore.
When one party promises improvements in 6 months, people will always choose it over a party that promises a stable and healthy environment in 50 years. Of course, the first one lies. But those lies work and get votes. So what do you do?
Why would have things been any different than today?
Eh, yes?
We've known about global warming since the 1890's when first scientific reports about it were published
This isn't a new thing, its just been swiped under the rug for decades because profits for a few people.
And before the capitalism bad crowd chimes in, every country ignored it unless you're willing to claim that the USSR was all about environmental protection (it was most definitely not)
Put in the words of that guy about hospitals closing "I don't believe it".
Just like they know them today but don't care because profits matter much more.
Moneh-moneh-moneh-money! Moooneyy!