Friday 3 November 2017 06.45 GMT
When UN climate negotiators meet for summit talks this month, there will be a new figure on the table: 3C.
Until now, global efforts such as the Paris climate agreement have tried to limit global warming to 2C above pre-industrial levels. However, with latest projections pointing to an increase of 3.2C by 2100, these goals seem to be slipping out of reach.
“[We] still find ourselves in a situation where we are not doing nearly enough to save hundreds of millions of people from a miserable future,” said Erik Solheim, the UN environment chief, ahead of the upcoming Bonn conference.
One of the biggest resulting threats to cities around the world is sea-level rise, caused by the expansion of water at higher temperatures and melting ice sheets on the north and south poles.
Scientists at the non-profit organisation Climate Central estimate that 275 million people worldwide live in areas that will eventually be flooded at 3C of global warming.
Asian cities will be worst affected
The regional impact of these changes is highly uneven, with four out of five people affected living in Asia.
Although sea levels will not rise instantaneously, the calculated increases will be “locked in” at a temperature rise of 3C, meaning they will be irreversible even if warming eventually slows down.
5.2 million people affected
At the end of a month in which it has been battered by unseasonably late typhoons and relentless rain, Japan is already confronting the threat posed by climate change-induced flooding.
Image modelling shows that swaths of Osaka – the commercial heart of a region whose GDP is almost as big as that of the Netherlands – would disappear beneath the water in a 3C world, threatening the local economy and almost a third of the wider region’s 19 million residents.
Millions of people live in the urban area surrounding Osaka. Sea-level rise will reshape densely and sparsely populated areas.