I've wondered about this very thing because of the weather the past few years. Remember that climate is not neccesarrily the weather on any give day, season or year, but what is expected or the norm. So are the current extreme patterns a new norm and a shift in climate? It is according to a panel of officials and scientists put together by the Union of Concerned Scientists. Climate scientist Katharine Hayhoe (Texas Tech) said, "It's a new normal and I really do think that global weirding is the best way to describe what we're seeing," Nikhil da Victoria Lobo of the reinsurance firm Swiss Re is quoted, "Globally what we're seeing is more volatility."
I think we will only be sure if this is the case is unfortunately looking in our rearview mirror. It is disturbing to think that this change could actually be noticeable in the space of years rather than decades. The irony is that while rapid change may get the public behind mitigation it would be an indication that the problem is much worse than expected.
While we're on this subject , here are the GISTEMP maps of surface temperature anomalies for March and April: