A combination of land subsidence and rising sea levels mean that “coastal infrastructure, such as port facilities in Boston’s Inner Harbor and Boston Logan Airport, will be at risk of flooding ... ” The city began addressing these issues back in 2004, with its report “Climate’s Long-term Impacts on Metro Boston.”

Water levels in Lake Michigan will go down. Temperatures will go up. Severe weather will increase. Water contamination from sewage overflow will be a problem. In response, the city is innovating -- for example, converting impervious to pervious surfaces to decrease runoff. It’s a start.

Because of a rising landmass, higher sea levels are not expected to challenge communities in the Cook Inlet area, including Homer. But increased precipitation could cause coastal erosion, storm surges, and debris slides. This small town is thinking ahead, writing climate change into its comprehensive plan and creating a fund for sustainability initiatives.

“Sea level rise threatens the very existence of the Florida Keys, owing to their low elevation,” according to the report. The effects are already being felt in places like Ramrod Key, above. In nearby Miami, the Biscayne Aquifer, the city’s main drinking water source, is threatened by sea level rise. “The city proposes efforts such as incorporating climate change into long-term planning.”

The world watched in horror when New Orleans flooded during Hurricane Katrina. That type of threat is still very present as sea levels rise, wetlands flood, and more extreme weather is forecast. Because of Katrina, the city is already actively working to prepare for future events, by elevating existing structures and zoning to steer development to less flood-prone areas.

Crosbie

Norfolk has been seeing an increased rate of flooding in recent years, as the coastal land subsides and sea levels rise. “The rate of annual sea level rise measured at Sewells Point in Norfolk is the highest of all stations along the U.S. East Coast -- nearly 4.5 millimeters per year.”

“Precipitation is projected to decline in southern Arizona by 5 to 10 percent by 2100,” says the report. That means more drought for Phoenix, where temperatures are already going up. The city is already using treated wastewater for crops, golf courses, and other purposes, and has decreased per capita water usage in recent years, even as population has increased.

Rising sea levels could threaten key infrastructure in the San Francisco Bay Area. Earlier snowmelt could mean less water during the summer, when demand is highest. Lots of people inside and outside government are working to address these challenges in forward-thinking San Francisco, with measures including a much more aggressive approach to water management.

Much of Seattle’s waterfront residential development, as well as its port, is at risk from sea level rise. In addition, its fisheries -- including salmon and shellfish -- are threatened by rising water temperatures and increasing acidification of marine waters. The city is actively studying the challenges to prepare itself.