He appears to be plotting balloon surface altitude vs RSS lower troposphere. That is not correct, he needs to use 850 mb or interpolate to match the lower troposphere definition. Also he could have looked at UAH.. Also he appears to be using an old RSS dataset, because they have a spike in 2015 which should show through on the 5 year MA.
So that's a few things worth checking. However it is great, now I've got the balloon data to play with as well. So to summarise, thanks for the blog link, but it is not definitive.