I had a very strange interaction online a couple of days ago. Some weeks ago I was invited to join a Facebook group entitled ‘Church of Hawking Year 2 AH’ (After Hawking) or something similar (they have now blocked me). I was invited by someone who apparently ran the Facebook page. Yesterday, they wrote a comment on some story on global warming, and in that they indicated that they didn’t know what an icecap was, by effectively stating that the Arctic sea ice was part of the northern ‘ice cap’. This is incorrect. They apparently didn’t know the difference between an ice cap, an ice sheet and sea ice. I attempted to put them straight but had forgotten the term ice sheet, which I had looked up some months previously for an article I wrote1, so I incorrectly used the term ‘ice cap’ for the Greenland ice sheet. Realising and admitting my mistake later, and at the same time receiving some derogatory comments, I googled it and came up with the definitions of these terms from the US National Snow and Ice Data Center (NSIDC)2. They are as follows:
An ice sheet is a mass of glacial ice based on land which extends over more than 50,000 square kilometres. They are of fresh water ice, as they come from precipitation. There are only two ice sheets currently on the planet. They are the Greenland and Antarctic ice sheets. During the last ice age, ice sheets covered much of North America and Scandinavia3.
An ice cap is a mass of glacial ice which is based on land and is less than 50,000 square kilometres in extent. They generally form in polar and sub-polar regions and are relatively flat and high in elevation. Like ice sheets, they are of fresh water ice as they too come from precipitation. Iceland has an ice cap and it is found on the southern part of the island and covers about 8,000 square kilometres4.
Sea Ice is frozen ocean water, but for most of the year it is covered in snow. Because it is so bright, it reflects about 80% of the sunlight that hits it, back into space. When it melts, the darker water absorbs 90% of the light hitting it5. This is one of the global heating feedbacks concerning climate scientists, as the amount of Arctic sea ice is rapidly decreasing.
Given that these people online were pontificating incorrectly about the cryosphere, the fact that none of them seem to have heard of the NSIDC is extraordinary. The person who invited me onto the Facebook page continued to spit the dummy, effectively accusing me of lying about the climate and eventually blocked me. It is an odd thing to be subject to abuse while attempting to politely enlighten someone when they have committed an error. It is something I have rarely suffered before, except from creationists and climate change deniers. In retrospect, to be blocked by this bunch is probably a bonus.