| CANCUN, Mexico
CANCUN, Mexico Climate negotiators left this tourist city upbeat about a modest deal to control global warming, but the world still faces daunting choices on how to cope with rising seas, health woes and mass migration.
Because nations are unlikely to make deep cuts in greenhouse gas emissions to prevent climate change, world leaders must work out how developing nations will adapt to more severe weather predicted in coming years that will hit food and water supplies.
Delegates from nearly 200 nations surprised skeptics when they agreed a pact in Mexico to set up a new fund -- with a goal of $100 billion in a year from 2020 -- for measures to protect forests, share clean technologies and help the poor adapt.
Until now, most efforts have been on curbing greenhouse gases from factories, power plants and vehicles -- not on adapting to a changing climate of droughts, floods and a creeping rise in sea levels.
The Cancun deal asks countries to submit ideas by February 21 about steps to set up an "Adaptation Committee."
Adapting to climate change will affect rich and poor nations but it is the latter that are likely to be hardest hit and will have to seek money to fund everything from research into drought-resistant crops to barriers against rising seas.
So deciding how to dole out limited donor funds among desperate nations will become increasingly difficult in the years ahead. Leaders will have to grapple with which climate battles they can fight and which are simply overwhelming.
"Adaptation will increasingly involve choices about what to preserve, since enormous amounts of resources might otherwise be wasted on the impossible," according to Dara International, a think tank that audited the impact of climate change around the world.
Nations currently spend $9 to control greenhouse gasses for every $1 they spend on adapting to climate change realities, according to Oxfam, the humanitarian aid organization.
"That is out of whack," said David Waskow, Oxfam's senior climate policy adviser. "We need discussions on adaptation that won't leave spending decisions to the whim of funders."
Kiribati, Tuvalu, the Cook Islands, the Marshall Islands and the Maldives are among the water-locked nations that could be erased from the map if sea levels rise, their leaders say.
Other poor countries such as Bangladesh, Vietnam and Sudan are also at risk from flooding, rising seas and food crises, according to the World Bank.
Environmentalists and scientists say the devastating floods that hit Pakistan and the soaring heat and wildfires in Russia this year are examples of the extreme weather the world will increasingly face.
Defending against such climatic turmoil could include building sea walls to defend against surging waters and relocating coastal communities further inland.
If global carbon markets take root that allow polluters to trade the right to burn fossil fuels, nations might use the revenues to fund climate mitigation projects.
"That is a bit into the future," said Norway Prime Minister Jens Stoltenberg who has been tapped by the United Nations to find a way to create the $100 billion fund. A global price on carbon of between $20 and $25 a tone would go a long way to reaching financing goals, he has said.
In the meantime, vulnerable nations might turn to a new panel conceived at the Cancun summit that encourages rich nations to share technology and know-how on adapting to climate change.
The panel will also consider climate risk insurance which many island nations believe is necessary to allow them to withstand and bounce back from disastrous storms.
"When Hurricane Katrina hit, that did not affect the United States as a nation. But when Hurricane Ivan hit, our entire economy collapsed," said Grenada Prime Minister Tillman Thomas, comparing the 2005 storm that wrecked New Orleans to the 2004 storm that flattened his country.
But the costs to curtail the greenhouse gases linked to climate change are in many cases matched by the expected costs of adapting to a hotter world. Rising sea levels will cost $100 billion a year by 2030 as some coastal areas are flooded or totally submerged, according to Dara International.
The U.N. panel of climate experts has said that sea levels may rise by 18 to 59 cms (7-24 inches) by 2100. If ice in Greenland or Antarctica melts fast, U.N. Secretary General Ban Ki-moon has said it could be up to 2 metres (6 ft 6 inches).
"There are going to have to be many tough choices made. We need, in the near term, to build communities to face the climate changes," said Waskow of Oxfam, which wants half of all future climate change spending to go toward adaptation.
(Editing by Russell Blinch and Alister Doyle)