Two filmmakers record a large chunk of glacier breaking off and sinking into the ocean while filming the award-winning documentary Chasing Ice. It was the single largest calving event that has ever been recorded. Over the course of 75 minutes, they watched almost five square kilometers (3 square miles) of ice break away. This isn’t just a little crust of ice either, it’s about 915 meters (3000 feet) The video shows a time lapse of what that process looks like over the course of a few seconds. At the end of the video, the filmmakers show what it would look like if lower Manhattan were sitting in that same area. It is a humbling feeling to see such a great expanse of ice fall into the water as if it were nothing.

Glacial retreat is just one of many parameters that scientists use when studying climate change. As global temperatures rise, the glaciers cannot hold the sea water as ice any longer. As they melt, the sea levels will rise. Scientists have calculated that sea levels appear to be rising at 3.5 millimeters (0.14 inches) over the last 25 years. On the surface, that sounds meager enough… unless you know how to multiply. Globally, sea levels are up as much as 8 inches (20 centimeters) in the last 100 years alone. Unfortunately, glacier retreat and subsequent sea level increase have sped up over the last two decades.

By 2100, it is estimated that sea levels will rise as much as 40-120 centimeters (16-48 inches). Unfortunately, because of all of the combining factors that play into glacial retreat and rising sea levels, more precise numbers cannot be given. On the upper end of that scale, millions living in cities like New York, London, Miami, and Los Angeles will be displaced. Entire islands could disappear. The changing ocean waters are also expected to impact the fish populations and could very well reduce the food supply. These consequences are going to be catastrophic.