On an evening in the Southern Hemisphere's late spring that was still cold enough for a jacket, Julie Arblaster joined about 100 other choral singers at the Melbourne Symphony Orchestra rehearsal studio to practice a new piece of music. Its name was "Fire of the Spirit."

It celebrated a female mystic from the 12th century whose words might have been spoken by environmental activist Greta Thunberg in the 21st: "The Earth sustains humanity. It must not be injured; it must not be destroyed."

Arblaster, an Australian climatologist, had just co-authored a paper about a weakening Antarctic polar vortex. She knew it would combine with a worrying set of conditions that can occur in the waters surrounding her vast country.