This is helpful to me (and many others, I'm sure) and I look forward to reading more. Subscribed.

This is factored in. The sea level rise comes from ice that is currently sitting on continental shelves, hence why Antarctica is a particular concern.

I've had exactly the same experience today, having been asked to complete a captcha (of a type I haven't seen before—rotating a 3D object) after every prompt. I'm logged in and a paying subscriber of more than a year. I assume it is a bug.