It would be nice to think the talk that "the end is nigh" as you so amusingly put it (and we could find a few hundred cartoons to illustrate that thought) is merely empty rhetoric. Unfortunately for us all, it is not.
Let's agree to treat the person of Greta, her nationality, age, modes of travel and emotions as irrelevant with regard to her message. We can also accept your assurance that you are not writing as a "middle-aged-white man-who's-triggered".
Starting with the letter from those 500 scientists: Of the 500, only 10 identified themselves as climate scientists, and of those, very few, if any, have peer-reviewed published work to back up their claims.
The others are engineers, geologists or work in other fields, including journalism and the wine industry. Some have been, or are, part of the oil and gas industry.
Six climate scientists who analysed that letter estimated its overall scientific credibility to be "very low", with one describing the content of the letter as "completely inaccurate, undocumented, and fail[ing] to bring proof for its claims".
By comparison, 97 power cent of all publishing climate scientists support the consensus on anthropogenic climate change. (https://en.wikipedia.org/wiki/Scientific_consensus_on_climate_change).
Moving on to "the UN has done this before": Severn Cullis-Suzuki (the Greta equivalent you mention) remains a Canadian environmental activist, and is a speaker, television host and author.
She holds a BSc in biology from Yale University and MSc in ethnoecology from the University of Victoria, where she studied with elders from the Kwakwaka'wakw First Nations.
Precociously, at 12, she addressed delegates present at the UN Conference on Environment and Development. In what way does this lessen the climate-change message?
You then suggest that "this" (presumably understanding the likely effects of climate change) is about "charging taxes for emissions".
Many might agree with you. I thought so too, back when carbon credits first became a thing. Carbon credits have muddied the waters for far too long. They came about because of the world's obsession with money to the detriment of pretty much everything else.
"Let's make them pay – then they will change their ways" does not work. But something needs to. Because climate change is happening, whatever the economy is or is not doing.
It can be seen in the rapid rise in the planet's average surface temperature, warming oceans, shrinking ice sheets and glaciers, seawater infiltration into land masses, and rising numbers of extreme weather events.
It is shown in the published data of climate scientists globally. There is indeed a "looming catastrophe", although you use that phrase flippantly. These are not just "climate fluctuations", though it would be great if they were.
Various solutions, or mitigations anyway, from the highly technological to the very simple, are being proposed.
Some, as Sophie Handford has "dared" to bring forward, are to do with the business of agriculture, but…agriculture forms the backbone of the New Zealand economy.
And there it is again – profit margins, exports, money. If climate change continues unchecked (and it is already almost too late to turn things around, even by means of overall de-growth) the effects worldwide, including widespread disease and eventual societal breakdown, will mean that the word "money" has no meaning at all.
Have you heard that all before?
*Glennis Moriarty is a wife, mother, grandmother, and former science teacher, author and editor.