"John Hall" wrote in message news
That's just the Arctic though. AIUI JohnD is talking about the sum of
Arctic and Antarctic.

Yes indeed, thanks John. Just to repost, the link for global SIE (based on
NSIDC data) is:

https://sites.google.com/site/arctis...t_byyear_b.png

On Friday, 4 August 2017 10:54:47 UTC+1, JohnD wrote:
"John Hall" wrote in message news
That's just the Arctic though. AIUI JohnD is talking about the sum of
Arctic and Antarctic.

Yes indeed, thanks John. Just to repost, the link for global SIE (based on
NSIDC data) is:

https://sites.google.com/site/arctis...t_byyear_b.png

Thanks for posting that link. I see what you mean now.
But the Arctic and Antarctic sea ice extents both seem to be on steady trend lines so I don't understand why their sum should show such a large change.