Rising of sea level due to

Im going to guess that you are asking why sea levels are rising?

The rising in sea levels is due to climate change. By burning fossil fuels such as coal or oil we produce green house gasses such as carbon dioxide which are causing the climate to become warmer. This is resulting in warmer seas and warmer winters meaning glaciers and huge amounts of snow and ice are melting. It is the melting of these that is causing a rise in sea levels.