Sea level rise has been an undeniable consequence of human-caused climate change. Global warming is driving this rise in two ways: thermal expansion of the oceans (water expands as it warms) and melting of glaciers and ice sheets. These processes are increasing in speed and are expected to continue unless emissions of carbon dioxide and other greenhouse gases (GHGs) are rapidly cut back.

In the past, scientists measured sea level changes by looking at tide gauges in ports and harbours. Today satellites can take more comprehensive measurements by bouncing radar signals off the sea surface to determine the height of the ocean. For example the satellites TOPEX/Poseidon, Jason-1 and OSTM/Jason-2 have provided detailed observations of changes in sea level. These measurements, combined with computer models, are used to make projections about future sea level rise.

These projections are based on atmospheric and oceanic general circulation models (AOGCMs) that simulate the physical processes that drive climate change, including sea level rise. They also incorporate future scenarios for GHG emissions.

Rising seas will affect coastal areas and people living there, destroying wetlands important for wildlife and making it harder to farm crops. It will also increase the power and reach of storm surges, causing flooding. This will hurt the economies of low-lying countries, especially those that depend on tourism. The world can adapt to slow sea level rise, but if the pace of rise accelerates, it will be much harder. This is why the task force emphasized the need to cut emissions.