When we think about long-term climate change, we often look only towards the end of our current century. The conversation is about what will happen by the year 2100 – which cities will be underwater, what the global temperature will be, how different the world will look. It leads to a bias that lets us forget a startling yet not-so-surprising reality: even if the entire world stopped emitting greenhouse gases today, the sea would still continue to rise for hundreds and hundreds of years.
Rising sea levels have become locked-in as an effect of climate change, which means that the future changes to come are irreversible. This is attributable simply to the fact that ice takes time to melt. It will be an ongoing process as the change of state catches up to its warmer environment.
With regard to rising temperatures, the most realistic estimate currently predicts an increase of 3.2 degrees Celsius by the year 2100. It comes from the IPCC (UN Intergovernmental Panel on Climate Change), which releases reports containing different possible scenarios for the future state of the environment. However, it actually is possible for the global average to stop rising after the year 2100. This happens in the most ideal scenario where carbon dioxide emissions are rapidly reduced and we eventually have a means of producing negative emissions (i.e. taking carbon dioxide out of the atmosphere) in the future. Meanwhile, all predictions from the IPCC (UN Intergovernmental Panel on Climate Change) show that sea levels can only continue rising.
The youngest people alive today will live to see 2100. Anything beyond then, we so far have no connection to. However, even though the big headlines stop after 2100, climate change doesn’t. As projected by the IPCC, “it is virtually certain that global mean sea level rise will continue for many centuries beyond 2100, with the amount of rise dependent on future emissions.”
Tl;dr the sea level will keep rising for basically forever.