Firstly, no one is saying what the Earth's temperature should be, just that as it warms, the ice will melt which adds to sea levels, that newly introduced fresh water changes the density and temperature of sea water which causes ocean currents slow, they stop transporting warmer temperatures from the Equator to the hemispheres which then cool since they only get heat from the sun. This is what caused the Ice Age. There are plenty of scientific papers you can read on this and what the temperature was in Oregon when the North American plate was part of Laurasia/Pangea...but would you believe them?
Climate change has always existed, no one has said that Humanity caused climate change, but we have affected it. To deny that the Industrial Age did not contribute to climate change is crazy. We've known that CO2 is a greenhouse gas for over 100 years (1856, by Eunice Foote). I don't understand the choice of not believing the science.