This week, University of Florida scientists discovered the sea level along the southeastern U.S. coast has risen far more quickly than the long-term rate globally, underscoring new concerns about the effects of climate change.
Increasingly, the phenomenon of rising sea levels has amplified fears over climate refugees — individuals forced to leave their homes due to changing environmental conditions in their respective homelands. Climate watchers estimate that at least 26 million people around the world have already been displaced, and that figure could balloon to 150 million by 2050, according to the Worldwatch Institute.
Relocating those populations cost money, raising the question of who will cover those costs as sea levels continue their uptrend. The rise in global sea levels has accelerated since the 1990s amid rising temperatures, with a thaw of Greenland's ice sheet pouring ever more water into the oceans, a team of international scientists reported last month.
In the U.S., the cost of climate change is expected to be steep. A Science study estimates that every one degree Celsius increase in global mean temperature will cost the U.S. 1.2 percent of its economic growth. Separately, a recent assessment by Lloyds estimated that flooding ranked high among the top five risks to global economic growth, and could cost upwards of $430 billion.
Mark Witte, a professor of public finance at Northwestern University, said climate relocation demonstrates a classic economic problem when it comes to addressing slow moving, long-term challenges.
"We're waiting for the tipping point," Witte told CNBC recently. "We're going to wait too long, and it'll be a more expensive fix in the long term than if we just did something now."
To be sure, skepticism abounds over whether a warming climate is being caused by human activity — including the Trump administration, which has come under fire for rejecting the landmark Paris climate agreement. Even a few true believers in climate change have argued the costs of implementing carbon reduction policies could have potentially devastating economic consequences.
However, for people like 27-year-old Panama native Diwigdi Valiente, climate change is "not a fairy tale anymore." In addition to washing away homes and schools on the inhabited islands, rising seas are set to engulf hundreds of Kuna-owned tourist beaches off the Caribbean coast, which locals use as their main source of revenue.
Valiente, part of an indigenous population called the Kuna, is one of tens of thousands of autonomous islanders who may need to relocate to the mainland within the next 20 years, as rising seas threaten to swallow their homes. Some Kuna are facing moves to the mainland even sooner than that as puddles of water form on the islands.
"There is zero infrastructure on the mainland right now," Valiente, who works for Panama's Ministry of Economics and Finance, told CNBC recently. "The Kuna will have to rebuild what they built up on their islands over the last 150 years, and who knows how much that will cost?"
Panama's government has pledged to help fund the Kuna's relocation. However, according to Valiente, the effort is not moving quickly enough, and may not cover the full costs.
Aresio Valiente López, Valiente's father who also serves as an environmental lawyer for the Kuna, estimated the environmental impact could result in a loss of about $3 million in revenue per year for the Kuna—which have turned to international organizations for financial assistance.
For millions of individuals living in low coastal areas across the world, and for the policymakers debating what to do and how to pay for it, climate change is no longer an abstract, far-off concept.
"We all thought this is something that was going to happen in 100 years or something," said Valiente. "But it's happening right now."
Long run options 'unaffordable'
In the U.S., some states have already received funding from the federal government. Last year, Louisiana received $92 million from the U.S. Department of Housing and Urban Development for two coastal resilience-building projects.
The state earmarked $48 million of that award to relocate 99 residents off the small island of Isle de Jean Charles, in what will be one of the first climate-induced relocation effort undertaken in the U.S. Louisiana also plans to use nearly $40 million to implement a program to shore up the state's natural disaster preparedness and recovery strategies.
Since 1955, 98 percent of the island's mass has been swallowed up, according to HUD, with relocation efforts expected to be completed over the next few years.
Pat Forbes, executive director of Louisiana's Office of Community Development (OCD), said there is a lot more to the project than just getting the people off the island.
"If all we do is get the people off the island, we have not succeeded," Forbes said. "We need them to be a community and hopefully even build a stronger community."
Mathew Sanders, the OCD's resilience program and policy administrator, said Louisiana is testing out policies and frameworks that could potentially be used by other communities across the country facing similar problems.
Louisiana, however, is just one recipient of federal aid. Other states haven't been as fortunate, at least not yet.
Philip Stoddard, the mayor of South Miami, said he does not expect to see financial assistance from the federal government anytime soon — even though one in eight homes in Florida could be underwater by 2100, Zillow data states.
"In the short run . . . the problem is almost overwhelming to the most clear-thinking of politicians, Stoddard said, as he blasted President Donald Trump's skepticism on climate change. Yet even still, the lingering issue of cost looms large in the debate.
"In the long run, the entire menu of possible solutions is unaffordable," Stoddard added.
At the current time, the mayor does not expect support from Florida, either, but said municipalities should meet with members of the community and come up with their own regional plans. Still, Stoddard said the problem with that approach was that "local neighborhoods are not very good at spending money on what they perceive as long-term problems."
Stoddard believes flood insurance rates — which have been subsidized for years by governments — will be the so-called tipping point for homeowners in the U.S.
When rates are allowed to rise to a level that matches the actuarial risk of flooding, homeowners will find they cannot afford their flood insurance and will pressure elected officials to take action, he argued.
"Homeowners will find themselves underwater literally and figuratively," Stoddard said.
--Reuters contributed to this article.