It doesn't follow that it's reasonable to express alarm. Decades of stability followed by sudden change is strong evidence against CO2 being the cause, because

It doesn't follow that it's reasonable to express alarm. Decades of stability followed by sudden change is strong evidence against CO2 being the cause, because growth of that in the atmosphere is a very stable process. It suggests a different cause, which means it's natural, most likely related to undersea volcanism. In which case it's unlikely to be dangerous, unless you think this is some sort of freak event like an asteroid strike. But then you're not talking about climate change.