If we stopped pretending climate change wasn't around we would have a much more sustainable planet. Climate change is causing glaciers and ice caps to melt and therefore putting more water stored as ice in the ocean rising sea levels as a consequence. There are also dangers to coastal regions getting flooded.
A cool graphic image showing what Earth would look like if climate change kept going.
(quick disclaimer, this image is not real and will probably never be real)
(quick disclaimer, this image is not real and will probably never be real)