"It has been a slow process that has been continuing for the last 15,000-20,000 years."

Factually wrong.  It has been 7000 years since the interglacial thermal maximum, and it should have been cooling naturally since then.  The 7000 year natural cooling trend  completely reversed itself 100 years ago.  Only humans could have caused that reversal -- all natural forcings are negative.

http://www.realclimate.org/images//Marcott.png

Ice melting has been accelerating in the last 100 years.  Glacier National Park, for example, had 150 glaciers in 1850, and that number has been reduced to 25.  

The Greenland ice  sheet (land ice) is losing 287 Gt of ice per year, and the trend of mass is steadily down.
https://climate.nasa.gov/vital-signs/land-ice/

In short, you are misrepresenting the facts to suit your political agenda.