Many of Alaska’s roads, runways, railroads and water and sewer systems will wear out more quickly and cost more to repair or replace because of climate change, according to a study released yesterday.

Higher temperatures, melting permafrost, a reduction in polar ice and increased flooding are expected to raise the repair and replacement cost of thousands of infrastructure projects as much as $6.1 billion for a total of nearly $40 billion — about a 20 percent increase — from now to 2030, according to the study, by the Institute for Social and Economic Research at the University of Alaska Anchorage.

The cost estimates are based on the needs of nearly 16,000 pieces of public infrastructure, including airports and small segments of roads.

The researchers speculated that in the distant future the costs would level off as the agencies adapted their practices to the warmer climate.

Temperatures have risen by an average of two to five degrees in different parts of the state in recent decades, and the changes have already been linked to problems like coastal erosion in remote Alaskan villages and wildfires. The researchers who wrote the report said their estimates for increased costs were based on “middle-of-the-road” forecasts for warming in a place where projects were designed to endure the cold.

“We assume warming temperatures mean infrastructure has to be replaced more often,” the report said. “It’s also possible the changing climate could actually increase the life of some structures, but we haven’t so far identified any such exceptions.”

The study is the first of its kind in Alaska, and its authors emphasize that it does not project costs for things like moving villages, protecting the Trans-Alaska Pipeline, fighting wildfires or protecting private property that may be affected.

“There are a million other issues related to climate change,” said Peter Larsen, a natural resource economist at the Institute for Social and Economic Research and the lead researcher for the report. “This is just one component, but it’s a critical piece because this is where all the goods and services come through the state’s economy, is through the infrastructure.”

Mr. Larsen said the most vulnerable places in the state were probably those built heavily on permafrost, the permanently frozen subsoil, whose average temperature is projected to rise above freezing in the future, potentially making the ground unstable.

“Those structures need to be investigated further,” he said. “What happens to costs when you cross that freezing point threshold?”

With no simple template for how to measure increased infrastructure costs from climate change, Mr. Larsen said he and other researchers had settled on studying how higher temperatures and precipitation changes affect the life span of materials. Then they combined that data with forecasts for higher temperatures and climate change in Alaska.

“There are other places that have done studies,” he said, “but Alaska is warming more quickly than any other place on the planet right now. There was nothing to this extent.”

He said he had begun the research “from scratch,” calling various state agencies. “I’d say something like ‘Can you tell me how much the changing climate over the last 50 years has changed this piece of infrastructure?’ ” he said. “On more than one occasion I had people laugh at me on the phone.”