A new report on climate change, released by the international charity Christian Aid, says Mumbai and Kolkata top list of the cities most prone to coastal flooding. The report – Act now or pay later: Protecting a billion people in climate-threatened coastal cities – released on Sunday, also underlines how the most carbon-emitting countries are also where major cities most prone to climate-induced risks are. Most of these cities are in US, China and India and highlights the danger of how more than a billion people are set to be exposed to coastal flooding by 2060 through a combination of sea level rise, storm surges and extreme weather.

According to projections for the year 2070, supported by the inter-governmental panel on climate change, Kolkata and Mumbai top the list of cities whose populations are most exposed to coastal flooding, with 14 million and 11.4 million respectively. The first seven cities on the list are from Asia, followed by Miami at number eight.

Miami is also forecast to suffer the brunt of the financial losses from coastal flooding by 2070, topping a separate list with an eye-watering $3.5 trillion of exposed assets. The US is likely to pay a hefty price for its world-leading per capita carbon emissions, as New York also comes in third with $2.1 trillion. China’s Guangzhou splits the two American cities with exposed assets of $3.4 trillion. In total, of the top 20 most financially vulnerable cities, half are from either of these two countries: four from the US, six from China.

Report author Dr Alison Doig, Christian Aid’s principal climate change advisor, said the figures should be a wakeup call ahead of next week’s World Humanitarian Summit in Istanbul (May 23-24). “We’re facing a head on collision between growth of coastal urban areas and climate change which makes coastal flooding more likely,” she said. “This perfect storm is likely to bring about a heavy human and financial toll unless we do something about it.”

Emphasising how the poor will suffer the most, she added, “Although financial cost to cities in rich countries will be crippling, the wealthy will at least have options to relocate and receive insurance protection. Evidence shows that from New Orleans to Dhaka, it is the poorest who are most vulnerable because they have the worst infrastructure and no social or financial safety nets to help them recover.”

According to Dr Doig: “There is a chance this horrifying vision of the future can be avoided. It is striking that the cities facing the most severe impacts are in countries with high contributions of carbon emissions. The first thing we can do is speed up the global transition away from dirty fossil fuels to the clean, renewably energy of the future.”

Already, ahead of next week’s World Humanitarian Summit, UN General Secretary Ban Ki-moon has called for the percentage of global aid spent on disaster risk reduction to be doubled to 1%. This would bring the figure to $1 billion. Christian Aid wants this to be raised to 5%. Dr Doig said: “This would go some way to help protect people in these cities now, and alleviate the threat for the billion vulnerable at risk from coastal flooding by 2060.”

In another ranking the report lists which nations will have the most people living in exposed coastlines by 2060. China tops the list, followed by India and Bangladesh. The UK comes in 22nd. Dr Doig said:

“In the UK we’ve experienced in recent years the winter flooding that has left large parts of the country deluged. But these figures show that it’s not just more rainfall we need to be wary of. The people living along our coastlines will become vulnerable to rising tides unless we do something about climate change.”

The report goes on to examine how men and women are affected differently by climate related disasters, with women on the whole suffering more acutely.