An interesting and upbeat read.
Greta Thunberg’s position is that (heavily paraphrased) the science of climate change has been settled for decades* and the time has come to deal with it. That the science really has been settled for decades is demonstrated in various ways including the simple fact that the core climate change science has not changed in decades and we really are running of time to get serious about the climate crisis (see the various IPCC reports).
* For examples of core climate change science that has been settled for decades, see https://en.wikipedia.org/wiki/Hockey_stick_controversy (1998), https://blogs.ei.columbia.edu/2018/06/26/james-hansens-climate-warning-30-years-later/ (describes 1988 research and controversy), and https://en.wikipedia.org/wiki/ExxonMobil_climate_change_controversy (
The story of Greta Thunberg’s April 14-25, 2019 rail trip to speak on the importance of getting serious about climate change and to promote Sweden’s “flygskam”, or “flight-shame”, movement.