What is climate change?

The climate—defined as the long-term average of weather conditions, including temperature and precipitation—is changing because the earth is warming. Heat-trapping greenhouse gases, including carbon dioxide, have warmed the earth and its atmosphere by one degree since the 1960s. As a result, evaporation has increased leading to higher average rainfall and more frequent, heavier rainstorms while, paradoxically, leading to drought in some places.

The surface of the ocean, too, has warmed by one degree causing thermal expansion and ice sheets in Greenland and Antarctica to melt resulting in an increasing rate of sea level rise. Indeed, since the 1920s, the global average sea level has risen about nine inches and the rate is growing exponentially—though experts disagree on how much and how fast. The National Oceanic and Atmospheric Administration believes that sea level could rise more than six feet by the year 2100. James Hansen, known as the “godfather of global warming,” predicts it could reach 16 feet by then and Harold Wanless, chair of the geological sciences department at the University of Miami, believes that it could continue rising a foot per decade from 2100 forward.

Climate change is expected to negatively impact the global economy, human health, agriculture, land use and infrastructure and increase competition for land, drinking water and food resources. In addition, climate change is beginning to adversely affect natural habitats, wildlife ecology, and individual species.

 

Why is southern Florida vulnerable to climate change?

Climate change disproportionately affects coastal communities. Coastal homes and infrastructure will flood more often as the sea level rises, leading to higher storm surges that move further inland. In some places, a particularly high tide can be enough to cause streets and homes to flood. These tidal floods are increasingly common and cause traffic backups, damage homes and cars, poison fresh water wells, kill lawns and gardens and overwhelm storm water drainage systems.

Southern Florida is particularly vulnerable to the effects of climate change because of its topography and geology. The region is flat and low lying with much of the area less than five feet above sea level. As a peninsula, the area is threatened by sea level rise from both the east and the west, through the Everglades. Worse, the peninsula is comprised of a porous plateau of limestone, which allows salt water to move freely—rising up into parks, corroding building foundations, and rendering traditional water management methods such as sea walls and barriers, ineffective.

Changing climate is also likely to increase inland flooding. Since 1958, the amount of precipitation during heavy rainstorms has increased by 27% in southeast Florida; more intense rainstorms increase inland flooding because rivers and canals can overflow their banks, and more water pools in slow-draining, low-lying areas.

 

How will climate change affect southeast Florida’s economy and infrastructure?

Climate change also threatens to damage southeast Florida’s economy. One conservative think tank predicted this scenario: “As [flood] insurance rates climb, fewer are able to afford homes. Housing prices fall, which slows development, which decreases the tax base, which makes cities and towns even less able to afford the infrastructure upgrades necessary to adapt to rising seas. The spiral continues downward. Beaches deteriorate, hotels sit empty, restaurants close.”

Indeed, tidally-induced flooding is already affecting coastal and inland communities by overtopping sea walls, pushing up through storm systems and raising groundwater levels producing flooding and threatening roads, bridges, beaches and overall quality of life. Beyond flooding, city planners expect that local communities will have to make significant investments to mitigate the impacts on public infrastructure, including the effects of shoreline recession, saltwater contamination of ground water and surface water supplies and elevated water tables.

 

How much will sea levels rise?

By 2015, climate scientists were predicting the local sea level would rise by 2.5 to 6.0 feet by 2100. After a review of technical data and scientific modeling, Broward County’s Climate Change Task Force—comprised of representatives from four counties within southeast Florida—determined that a projection of 3-to-9 inches of sea level rise (from a baseline of the year 2000 level) by the year 2030 should be used when considering short- and long-term plans and remediation. They also recommended a projection of 10-20 inches of sea level rise by 2060 and a projection of 24-48 inches of sea level rise by 2100 for long-term planning. Nevertheless, while there is scientific consensus that sea level rise along the coast of southeast Florida will be significant, the timing and level is impossible to precisely predict, forcing communities to choose among a host of differing projection ranges.