Climate Change and the Oceans

Why We Care: Global Warming's Impact

In the past century or so, global mean temperature has risen about 1°C. This is much smaller than our own experience of day-to-day changes, so why all the fuss? In fact, for many people, if you offered them warmer weather they’d take it.

One problem is, the trend towards warmer temperatures is accelerating. Over the next century, most models predict a global average rise of 3°C (~6°F) and perhaps as high as 6°C (10°F). Such large changes in annual-averaged temperatures would cause multiple problems for the Earth, including ecosystem dislocations and species extinction, sea level rise, and possible changes in the frequency and magnitude of severe weather events. The impacts of climate change are potentially large and adverse, but remain sufficiently uncertain that quantitative estimates are not yet possible.


Effects of Ocean Warming:

A beach in the Southern Caribbean, completely covered by broken coral heads from offshore reefs damaged by a combination of warming and severe storms. Ocean Warming Impacts Ecosystems:
  • Corals have been damaged by increased temperatures and by invasions of predatory starfish that thrive in the warmer water.

  • Fish species have been found off Alaska’s North Slope that had previously only occurred in the Bering Sea, much farther south.

  • Penguin rookeries off Antarctica have suffered damage as the sea ice used for roosting breaks up.

  • Massive algal blooms have occurred in the Bering Sea as a result of increased water temperatures.

  • Loss of sea ice is causing population stress among species such as polar bear that rely on pack ice as habitat.

  • Thermal stress on commercially viable species already threatened by overfishing.


Effects of Sea Level Rise

The present rate of rise is a few mm per year, or a few cm over ten years, or something like a foot per century. Sound benign? It’s not!!

A rise in sea level causes:

  • Enhanced erosion of coastlines, especially (but not only) by storms

  • Loss of shallow marine habitats such as coral reefs and coastal wetlands

  • Saltwater intrusions into the groundwater table

Basically, as the sea level rises, land disappears. Populous low lying areas like Bangladesh would suffer the worst. Millions of people could be displaced around the world. The IPCC estimates that the mean annual number of people flooded would increase several-fold (somewhere between 75 to 200 million) for a mid-range sea-level rise (40 cm).



Loss of habitat/change in ecosystems
As sea level rises, the narrow ribbon of the coastal zone will disappear or change more rapidly than either the ocean or land. Thus, species that rely on foraging in the coastal zone may be the first to experience the sea level rise. The sandpipers, red knots, and turnstones seen here on a beach near Cape May in the Delaware Bay will face declines in horseshoe crab eggs, their principal food along these shores. Poor foraging here will affect the success of their annual flight from South America to the Arctic. (Gary Braasch, "World View of Global Warming").


Coastal Erosion

Coastal Erosion north of Miami, on a clear day in April 2001, by a normal high tide.

Coastal erosion is a fact of life around the globe. This photo, by Gary Braasch, shows erosion occurring on a routine day, with a normal high tide. What might happen as sea level rises, and possibly the severity of storms increases?

Many low-lying areas of the US East Coast are already threatened, including Florida, the barrier islands of the Carolinas, and major population centers surrounding Chesapeake and Delaware Bays. Rising sea levels will exacerbate the already serious problem and threaten additional areas of the East Coast and Gulf of Mexico.


The potential financial cost of the loss of presently valuable real estate in the eastern and southern US is enormous. For other nations, however, the dislocation of rising sea level and coastal zone loss is potentially catastrophic. Areas of Asia and Africa stand to lose large regions of their most productive agricultural land, without the economic capacity to relocate the regions’ peoples or crop production. Many small island nations of the Indo-Pacific face an even more complete loss of their territory.


To see more impacts of global warming, visit Gary Braasch's World View of Global Warming website.


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