Someone asked me this recently. I think the rhetoric has become more violent on the denialist side, and remains the same on the acceptance side.
The IPCC has remained somewhat conservative and forensic-only in its rhetoric. Sites like 350.org have remained the same.
The reason for the ramping up of denialist rhetoric is that the facts remain the facts, and screaming hasn't made them go away.
In a sense, the acceptance language has been nowhere near effective enough. This is not because it isn't violent enough, but because
1. The IPCC and subsequent PR (including the websites) made a fundamental mistake.
2. The acceptance language is too much wedded to avoiding a disastrous future. The disaster has already occurred.
On (1) the mistake was that everyone (including the IPCC) allowed Frank Luntz, a conservative PR strategist, to define (falsely) “global warming” versus “climate change.” In 2003.
Now this is used as a weapon to beat the scientists with. “Oho--they changed it from global warming to climate change. Because they were wrong!”
In reality, scientists have used climate change since the 1950s. More recently, what was already the case in Gilbert Plass's quite accurately predictive 1956 paper, namely that humans are responsible, and that the climate change in question is due to an increase in global temperature, we have begun to use the term global warming. Since the later 1980s. That's when I remember first hearing it on the radio. Some time around 1988. This is when the IPCC (the CC means climate change) was founded.
Again: climate change has resulted from global warming.
The fact that “the climate has always been changing” is (1) irrelevant and (2) a way of watering down the meaning of this particular phase.
Ecology people who use the term “climate change”: you are now in Frank Luntz's world. Do you not want to be in it? Insist on calling it what it is, at least as a hyperobject: global warming.
I conclude: the rhetoric on the acceptance side is not nearly violent enough. This violence should not be in the form of stridency about the future. It should be ruthlessly insisting on the truth, which is that the catastrophe has already happened. We now have to figure out what on Earth to do with this knowledge. Not “brace ourselves for” anything as the New York Times wrongly puts it in a piece on my friend Stephanie Lemenager.