Oxfam warns the current relief system can barely cope
The number of people hit by climate-related disasters is expected to rise by about 50%, to reach 375m a year by 2015, the UK-based charity Oxfam says.
Current humanitarian systems are barely able to cope, an Oxfam study contends.
It warns agencies are in danger of being overwhelmed by events such as flooding, storms and drought.
The group called for a radical shift so that humanitarian aid is sent impartially, instead of on the basis of political or other preferences.
Oxfam's Rob Bailey told the BBC a big increase was needed in aid spending, but that the problem was not just about the amount of money.
"We need to see that money spent in better ways," he said.
"At the moment, poor people in the developing world who are facing up to these disasters, they are almost facing a kind of lottery on a global scale."
He said that in 2004, the equivalent of more than $1,200 (£823) was spent on each victim of the Asian tsunami, compared with just $23 per person for the recent crisis in Chad.
"There's a huge mismatch in where the money goes," said Mr Bailey.
Oxfam is also calling for a greater focus on helping countries and communities to prevent, and prepare for the suffering that climate change will cause.