The figure is four times more than original predictions and is due to governments failing to address the urgency of the crisis, according to international experts.
Warwick District Council is holding a ballot on May 7 over a £3m annual climate action plan.
The Swedish activist will be speaking at Bristol Youth Strike 4 Climate on College Green in the city.
By Zak Derler, Desmog UK
Tories say that regulation will make the UK less competitive. But climate-driven floods and heatwaves already cost Britain billions.
US researchers identified rising maximum temperatures as the key threat to animals and plants, which both face a similar risk of extinction.
Environmentalists have warned that climate change cannot be tackled by damaging nature.
North Somerset Council turned down a planning application to expand Bristol Airport because of environmental concerns.
Boris Johnson faced criticism on the issue from Labour leader Jeremy Corbyn during Prime Minister’s Questions.