The city is taking steps to prepare for the significant impacts of global climate change, but moving the route of Honolulu’s rail line more inland is not one of them, Mayor Kirk Caldwell said Monday.

Meanwhile, Caldwell and key scientists blasted President Donald Trump’s administration for “trying to bury the bad news” contained in the federal government’s comprehensive National Climate Assessment by releasing the report at the end of the day on the Friday after Thanksgiving.

Oahu is already seeing the effects of rising sea levels, from the coastal erosion along the North Shore caused by increasing higher surf to flooding during king tides in Mapunapuna and elsewhere, Caldwell said.

“We need to take action, (but that) does not mean we retreat from the urban core,” Caldwell said, standing at a pier in Honolulu Harbor. “I don’t think we’re going to leave from this place, nor are we going to leave from Kaka­ako with these towers and the infrastructure that we put in, or Waikiki or this pier.”

“We’re going to need to harden in certain areas, raise the height and elevations of our harbors and our lands piecemeal,” he said. “Sometimes the building may go higher — the footprint — or maybe … the first floor of the building may be surrendered to tides and then the streets will get raised.”

He added, “The investment, the infrastructure, the real property values are just too tremendous to do that, But we need to do things to protect these areas by raising the height of the land and other things we’re going to be looking to from our scientists.”

In more rural areas such as the North Shore, “perhaps we retreat, we give our beaches a chance to live by eroding and allowing the sand to stay,” the mayor said. “But we may have to give up homes, we may even have to give up roads. It doesn’t have to happen tomorrow, but we need to take the action to have it happen perhaps in the next 20, 30, 40, 50, 60, 70 years.”

Caldwell said alarms raised about the impacts of sea level change on the city’s $8 billion-plus rail project are coming from the project’s opponents and that it’s unrealistic to consider changing its route, which is slated to run through a section of Nimitz Highway next to Honolulu Harbor.

“If we’re talking about relocating rail, then we’ve got to talk about relocating our financial district, our harbor, our airport and Waikiki,” Caldwell said. “Mayors around the world, mayors in our country, they can’t relocate their cities, so they’re raising podiums and they’re raising street to address that over the long run.”

In Honolulu such a shift “would be so prohibitively costly it will never occur,” he said. “So the alternative is, over time, to raise the level of building and podiums.”

Rail designers are already taking climate change into consideration, Caldwell said. “The podiums and the stations are raised above what they’re estimating to be the sea level rise. And because it’s elevated in terms of the rail line itself, it’s high enough for even when you raise the roads for trucks, buses and other things to go on.” To shift farther inland from Nimitz now would essentially kill the effectiveness of the project, he said. “If you do that, it’s dead. It ends at Aloha Stadium or it ends at Middle Street, and you have half the ridership. That’s not resilient, that’s not sustainable.”

Trump, asked by a reporter Monday in Mississippi about the report’s conclusion that climate change would have severe negative impacts on the economy, responded, “I don’t believe it.”

Josh Stanbro, Honolulu’s chief resilience officer, said “the science is clear and has spoken.” Stalling on making changes to meet climate challenge only costs the government and taxpayers more money. “It’s going to reduce our economy by 10 percent.”

Chip Fletcher, Honolulu Climate Change Commission vice chairman, said people need to cut their carbon footprint by 50 percent by 2030 and then another 50 percent by 2040 and then again by 2050. “So by midcentury we are essentially operating as a carbon-free community on the planet,” he said. The report’s chapter on Hawaii and “U.S.-affiliated Pacific Islands” can be found at 808ne.ws/2TKVOFo.