The term 'refugee' does not even appear in the article.
... and while people do talk about 'climate refugees', nobody is talking about them 'overwhelming us'. And FYI it definitely does not take too many people to overwhelm a social system with benevolent impetus, as we saw starkly in Sweden, 2016.
As for the materiality of the article and what should set off alarm bells:
"“For example, it appears that the USA is entering a long period of decline in many aspect of its society, with a potential for a more rapid collapse in the coming decade,” said Steffen.
"Samuel Alexander, a lecturer with the University of Melbourne and research fellow at the Melbourne Sustainable Society Institute, told Voice of Action that the coming collapse would not be a single black or white event.
“With respect to civilisations, what is more likely is that we have entered a stage of what JM Greer calls ‘catabolic collapse’ – where we face decades of ongoing crises, as the existing mode of civilisation deteriorates, but then recovers as governments and civil society tries to respond, and fix things, and keep things going for a bit longer,” said Alexander.
“Capitalism is quite good at dodging bullets and escaping temporary challenges to its legitimacy and viability. But its condition, I feel is terminal.”
"“As economies deteriorate and as inequalities deepen, more people get disenfranchised, incentivising resistance and sadly sometimes making people look for scapegoats to blame for new or intensifying hardships (e.g. the so-called alt-right),”"
“I think global capitalism is realising that the parasitical nature that has emerged (where the top 1% own the vast majority of the world’s wealth), can only be sustained for so long,” said Buckley"
We have:
A) America in social decline (political statement)
B) the other boogey man 'capitalism' as the root cause obviously!
C) The 'alt right' (are we talking about the environment here?)
D) Researchers work cancelled for ostensibly political reasons, which is not good, but it's also not objective either.
So the problem with the article, is that a lot of the authorship is deeply ideological. This is hard issue to escape when trying to put an economic value of such things as 'pollution and traffic' vs other elements.
Far too many references to their representation of 'inequality', and major gaps in their assumptions as to how that leads to social decay, for this to be a serious treatise on climate.
And of course, no mention of Nuclear Energy, which is odd, given 'existential threat' you'd think we'd try to use something that is already fairly well proven.