Today is the feast day of Saint Pope Pius IX , who is noted for many things, perhaps the most lasting is Vatican I which defined the doctrine of papal infallibility.
Still widely misunderstood (and deliberately misconstrued by some), it has been confused to mean that the pope's opinions on everything from politics to sport teams are divinely inspired to be free from error. Not so. The dogma of papal infallibility is rather specific and has only been formally invoked one time in church history to proclaim the dogma of the Assumption. (The dogma of the Immaculate Conception was declared by Pius IX before the formal passage of the doctrine of Papal Infallibility.)
The doctrine of papal infallibility states "when, in the exercise of his office as shepherd and teacher of all Christians, in virtue of his supreme apostolic authority, he defines a doctrine concerning faith or morals (ex cathedra or "from the throne") to be held by the whole Church." It is hard to construe papal opinions on politics, global warming or interviews granted on a plane to the press as meeting such criteria. Vatican I itself was adjourned due to warring armies invading the papal states, putting governmental decisions made by the pope and the Vatican in critical perspective.
The inerrancy of the Church's teachings in faith and morals are ensured by the inspiration and guidance of the Holy Spirit - good news for all faithful Catholics.