Well,
climate change is in the news again ...
Of course, the presence of the so-called proxy is not infallible, but if they're looking at a sufficiently long period of time, and the coverage matches currently available historical climate data, then there is a high probability that they're right. In which case, we might be in for some "new" oceanfront property.
Personally, I think the stated grand objective of getting ice coverage data spanning the past million years may be pushing reality, but what do I know.