There's no doubt the Earth's been getting warmer in fits and starts, since the end of the last ice age. However, there's the flaw in the alarmists theories right there in that sentence - "fits and starts". The increase hasn't been on a relatively smooth upward trajectory; there's an irregular cycle built in, and no-one can explain the reasons behind the variability. Paleo-climatology has a stab at it, and there are some plausible theories, some "best-guesses", and some downright manipulation and cherry-picking of data, like Mann et. al.'s "hockey-stick". But there's no proof as to what caused the variations - there cannot be. Climatologists are looking back through a murky and distorting lens, and one which might be pointing in the wrong direction, or looking at the wrong data.
Let's look at some real data then, and see how the "x is accelerating" claims stack up. First temperature data, because most or at least may think this is the main indicator of things to come.
|Latest Global Temps - UAH Satellite data to February 2012|
|HADCRUTt3 variance-adjusted global mean, 1979-present (Source: Wood for Trees)|
Where's the acceleration, dude?