With $1tn a year needed, we analyse how best to fill the gap, from wealth taxes to levies on flying and oil extraction

Countries meeting in Baku, Azerbaijan, for the Cop29 climate summit are under pressure to find ways to raise money to help poorer nations cut greenhouse gas emissions, shift to a low-carbon economy, and adapt to the impacts of extreme weather.

At least $1tn a year is needed. Developed countries are willing to ensure about half of that is provided from public sources, leaving a large gap that countries are hoping to fill with other sources of cash, known as innovative forms of finance.