Earth’s collapsing atmosphere

At www.physorg.com/print198429352.html there is a report on a paper at Geophysical Research Letters June 19th which says there was a contraction of the  thermosphere during the deep solar minimum of 2008-9. It is known to cool and shrink when solar activity is low – but in this instance, the collapse was almost 3 times greater than low solar activity by itself can explain – from their mathematics. The thermosphere lies between 90 km and 600 + km in altitude, the realm of meteors, aurorae, and where satellites orbit the earth. It is also where solar radiation makes first contact with the earth. When the Sun is active it warms the thermosphere causing it to puff up – but when activity is law it shrinks. Solar activity for the last couple of years has been low – sun spots became scarce and the thermosphere contracted. It is being claimed the collapse was too great to blame entirely on the Sun and so other factors need to be taken into consideration. The obligatory mention of C02 is made where it says even increased levels of that gas cannot be blamed, even though C02 warms the lower atmosphere – but it is thought it cools the upper atmosphere. Even taking C02 into consideration the numbers don’t add up – so what else is involved?