Climate change is coming ashore in Florida, and that's a fact.This is the clear message from the just-released National Climate Assessment, the most comprehensive report ever on climate change from the U.S. government. The report gives a detailed look at how climate change is raising sea levels along the coast and further states how carbon pollution will drive weather to extremes across our country — from more dangerous wildfires and crop-dwindling droughts to more intense flooding and stronger hurricanes.Since 1859, scientists have shown that greenhouse gases, like carbon dioxide, trap heat. Today we are repeating their experiments on a planetary scale, increasing carbon emissions 30 percent in the last 30 years.Global warming is melting glaciers and ice sheets, and seawater is expanding as it heats up. These changes, in turn, are causing sea levels to rise, a threat that is particularly acute for Florida with its low elevation and 1,200 miles of coastline. Rising seas are already affecting our infrastructure, beaches and freshwater supply.Whether Democrat or Republican, Florida residents cannot afford to ignore the evidence of climate change. Consider the facts below. These aren't climate projections; these have already happened.• Since the 1960s, sea levels along Florida's coasts have risen 5 to 8 inches.What do a few inches matter? It turns out a great deal. Take Miami, for instance. According to Jayantha Obeysekera with the South Florida Water Management District, 60 years ago a matrix of canals with flood gates were installed that were designed to handle 6 inches of higher water levels. When stormwater threatened to pour onto roads and into our homes, engineers could open the gates and use gravity to drain it into the ocean. Today gravity is not on our side: Now if some gates were to open during high tide ocean water would flow inland.• Salt water intrusion is making water from underground freshwater wells undrinkable.As sea levels rise, salt water from the ocean is seeping through porous limestone into underground freshwater supplies. U.S. Geological Survey data shows that near Fort Lauderdale salt water intrusion has crept nearly 6 miles inland. This has forced water management districts and local governments in South Florida to abandon wells and seek freshwater further from the coast. The NCA report highlights how Hallandale Beach has abandoned six of its eight drinking water wells and now pays to get half of its water from Broward County.• The ocean is warming and turning acidic, becoming less hospitable to coral reefs and fish.Economically important fish like snapper and grouper depend on healthy corals to survive, but our carbon pollution is putting reefs and fish at risk. The NCA report finds that one-fourth of emissions are being absorbed by the oceans, resulting in surface waters that are 30 percent more acidic than before the Industrial Revolution. In addition, the Environmental Protection Agency states that oceans are absorbing 80 to 90 percent of heat from global warming. These stressors are contributing to more extensive coral bleaching events that can cause reefs to die, threatening the long-term viability of Florida's fishing and tourism industries.Those are just the facts for what we have experienced. They are just the beginning unless we mount a strong response, starting now.Local officials in cities and counties are leading the charge to prepare their communities for climate change. Partnerships like the Southeast Florida Regional Climate Change Compact, which represents counties with 5.6 million people, have put strategies in place to avoid urban flooding and protect critical infrastructure. Officials in Tallahassee need to establish a statewide climate strategy to ensure Florida continues to thrive. State-level action — from offering coordinated guidance to providing financial assistance — can help local agencies deal with climate-related problems today and in the future. Florida can also embrace commonsense policies to cut emissions, like a renewable portfolio standard that would bring clean, affordable energy such as solar to our citizens.Climate change is one of the greatest risks facing our society, and Florida is already feeling its effects. It's time to follow the facts and take a sensible approach to address this urgent problem.Lee Thomas served as Environmental Protection Agency administrator under President Ronald Reagan from 1985-89. He recently retired as CEO of Rayonier Corp. and currently serves on the board of World Resources Institute. He and his wife, Dorothy, live in Jacksonville. He wrote this exclusively for the Tampa Bay Times.