Global Warming: Sea Level Rise
Written by YeSeul Kim, Erika Granger, Katie Puckett,
Cankutan Hasar, and Leif Francel
Sea Level Rise
The main factors affecting sea level rise are thermal expansion of the oceans, melting glaciers, and melting icecaps. These are all symptoms of global warming. As the ocean, or any liquid, increases in temperature, it increases in volume as well. This process is known as thermal expansion. Glacial and icecap melting occurs when there is net loss of water from the body of snow and ice; that is, if more water melts off of the glacier or icecap during the summer than is accumulated through precipitation (snow) during the winter. (EPA, 2000)
Types of Sea Level Rise
According to Barry R. Lewis (2000), there are two types of sea level rise: eustatic and isostatic. Eustatic sea level rise responds to major climatic change and possibly affected by global warming. Isostatic sea level rise is a localized representation of vertical displacements of land surface with respect to sea level.
Global Sea Level Prediction
Sea level rise from any given source varies based on which model was implemented. The most often cited models that predict sea level rise are MPI, CCCma, GFDL and Hadley-CM3. The range of data arises from many uncontrollable and unpredictable factors that influence sea level rise. Such factors include climate, global warming, thermal expansion, future development of technology and amount of green house emissions. Each model makes different assumptions which add to some uncertainty in the results. However, to have the most accurate number, the average of the ranges was calculated. Sixteen different sources of sea level rise predictions a hundred years from now or 2100 were compiled. Primary sources included reports from the International Panel on Climate Change (IPCC), Environmental Protection Agency (EPA) and NOAA. The data ranged from extremes of .02 meters of sea level rise (Walsh, 2002) to 6 meters (AGI, 1994). After omitting the upper and lower outliers, the average of the ranges indicate that sea level will rise .944 meters.
This box and whisker plot delineates the 50% range of the compiled sea level rise is .48 meters to 1.94 meters. The plot omitted the outliers, which were indicated with red circles. The median is .55 meters, while the average is .944 meters.
Models and Their Uncertainties
Hadley-CM3 is considered “one of the most state-of-the art greenhouse models” that predict positive temperature trends (Douglass, 2004). However, existing observational data shows the contrary trend since 1979. The authors of this report believe one of two alternatives that could explain this phenomenon. First, the Hadley-CM3 is correct and all observational data sets must then be incorrect. Otherwise, the “[model does] not fully capture the multitudinous climate effects (including various feedbacks of an increase in greenhouse gases” (Douglass, Pearson, and Singer, 2004).
Stone, researchers at MIT who developed the
MIT-2D model, believe that uncertainty in heat uptake by the deep ocean
key factor for the uncertainty in models. The uncertainty in the rate
uptake by the deep ocean has not been included in the projects of
change made by the IPCC [model] (Houghton, Jenkens, and Ephraums,
following table shows the variability in four different models.