Global sea level rose during the 20th century, and projections suggest it will rise further and at a higher rate during the 21st century. Dr. Suzanne Moser, a Social Science Research Fellow at the Woods Institute for the Environment at Stanford University and a Research Associate at the University of California-Santa Cruz, Institute for Marine Sciences, has warned that “the impacts of sea level rise are already being felt widely.” So why are sea levels rising? Simply stated, the climate is warming, and a warming climate causes sea level to rise primarily by water expanding in a warming oceans and melting land ice, transferring water to the ocean.
The warming climate is commonly referred to as “climate change.” The most general definition of climate change is a change in the statistical properties of the climate system when considered over long periods of time, regardless of cause. Accordingly, fluctuations over periods shorter than a few decades, such as El Niño, do not represent climate change. The term sometimes is used to refer specifically to climate change caused by human activity, as opposed to changes in climate that may have resulted as part of Earth’s natural processes. In this sense, the term climate change has become synonymous with anthropogenic (the influence of human beings on nature) global warming. Whether or not climate change is a reality should not be confused with the uncertainty associated with climate change science, particularly the magnitude and timing of impacts from climate change, such as the amount of sea level rise and how it will unfold over time.