evidence: Even if we stop all greenhouse emissions today – which is not exactly realistic – sea levels will continue to rise. That’s not to say that what we do doesn’t matter. In fact, it matters a great deal. But the sea level rise we see today is the consequence of global warming that started from emissions released decades ago. Large bodies of water like the oceans have a great heat capacity – they warm up slowly and keep that temperature for a long time. This means that changes in sea level lag behind warming of the atmosphere. [...] How far the oceans rise will depend a great deal on what we do in the next few decades. Whether emissions can be restrained and sharply reduced will mean the difference between manageable disruption and catastrophic inundation. If we take action now, we’ll save and improve the lives of those 680m people who live in coastal areas just 10 metres above sea level. [...] How much sea level rise the world can expect by 2050 is quite well known. Everything after that depends on further emissions. To plan for the worst, structures built by humans should be adapted to accommodate for potentially significant sea level rise in future. In Northern Germany, so-called "climate dikes" have already been built. They have a wide foundation that means they can be built higher depending on the extent of sea level rise in the next few decades. Designing and building infrastructure with future change in mind demands investment today, but it will save lives and money in the long run.