Short answers, pulled from the story.
The first governmental climate emergency declaration was made by the City of Darebin in Melbourne, Australia, on the 5th of December 2016. It was put forward by Trent McCarthy, an Australian Greens Councillor. The declaration was encouraged by a Climate Emergency Declaration petition launched in Australia in May 2016.
As of May 2022, more than 2,100 local governments in 39 countries had declared a climate emergency. The populations covered by those jurisdictions amounted to over one billion citizens.
Oxford Dictionary chose climate emergency as its word of the year for 2019 because usage of the term soared more than 10,000% between September 2018 and September 2019. The dictionary defines it as a situation in which urgent action is required to reduce or halt climate change and avoid potentially irreversible environmental damage resulting from it.
On the 5th of November 2019, BioScience published an article endorsed by more than 11,000 scientists from 153 nations declaring that planet Earth is facing a climate emergency. The article warned that the world's people face untold suffering due to the climate crisis unless major transformations to global society occur. By July 2021, more than 2,800 additional scientists had signed the declaration.
Critics argue that climate emergency declarations can justify concentrating power in executive institutions, potentially bypassing democratic checks and balances. Researchers Gills and Morgan (2020) described the pattern as a successful failure, with symbolic commitments failing to deliver emissions reductions at the required scale. There are also concerns that emergency rhetoric can generate eco-anxiety, discouraging individuals from pursuing practical solutions.
The Senedd, Wales's parliament, became the first parliament in the world to officially declare a climate emergency on the 1st of May 2019, passing a declaration the Welsh Government had made on the 29th of April 2019.