If no one did anything to help climate change, how long would it take for the whole world to be flooded?

What a thought-provoking question!

As per my understanding, the whole world will not be flooded. Because the estimated global sea level rise is about 70 meters when all the mountain glaciers and ice caps of Antarctica and Greenland melt; however, our coastal cities would be flooded and some small islands would sink. This would result in significantly smaller land and completely different coastlines. However, scientists are still trying to calculate the exact volume of glaciers and ice caps on Earth.

Furthermore, the scientists who study sea level changes in the past, found that the Antarctic ice cap has survived much warmer times than current warming. Therefore, it is likely that all the ice may not melt completely. The main concern is that some parts of the West Antarctic ice caps and Greenland may melt completely. Scientists are still researching how, when and under what conditions this might happen.

So, the short answer to your question would be, we're still working it out!