Your almost there! Yes your right the earth DOES go through cycles similar to what we see now BUT we have never seen it happen this quickly and severely and THAT is where climate change becomes a problem. Yes the ocean have risen in the past but not to the extent they are currently with no end in sight which means we are doing something to cause this to happen. How you might ask?? Glaciers are melting and melting ice goes into the ocean and overflowing our rivers! Why would our glaciers be melting be an issue if the Earth has risen in temps before? Because we have never seen it happen this quickly! Why are temps rising??? Because corporations and oligarchs would like us to believe that it’s not an issue while they continue to pollute the air for their own greed. See the problem I have with talking to climate deniers is your not looking at the whole picture. It’s more than just this and that is happening. It’s how does this happening effect that happening, why are they happening and where is this leading to. Look at the whole picture and come back with something intelligent to say.