I think it was intended to make fools of the Global Warming "deniers". Instead it provided some proof that the "deniers" are actually skeptics.

I first read it from a link from Junk Science. I click on the link without reading the commentary at the site. While reading it in the beginning I first thought it some of it was plausible, but I also thought it was quite strange. I could tell that the writer was a believer in global warming, if nothing other then the general assertion that global warming was caused solely by CO2- no one serious, even the "serious" believers hold this view. So, maybe, the writer was an idiot, or bad writer, or trying to appeal to popular public opinion- or all the above.
I read on.
Next the test to determine how much CO2 the bacteria produced was highly suspicious in a number of different ways. First, it would been very difficult do to this at all properly, second even if done right there would been huge inherent margin for error from such a small sample- plus unless there was massive and detailed survey of ocean floor that I was unaware of- a even perfect measuring of the sample wouldn't give you much more than broad ballpark number.
I continued reading until got to the graph showing global temperature and human emission of CO2.

As it happens, I was earlier google searching for such a graph on total human emission over the decades [without success]. The graph on human emission of CO2 looked somewhat credible, but then I looked at the temperature graph. Then looked at it again. At that point, I thought either somehow I'm reading the graph wrong, or it was gross error, or it was a joke.
I went back to Junk science and then saw the commentary that said it was a hoax.

I don't think the Hoaxer was trying very hard to make it seem realistic. Instead he wanted to be able to say "How could you believe in such obvious hoax"? E.g. the temperature graph isn't even close. "You think the global temperature has risen more than 3 C over last Century and you *still* aren't tiny bit concerned?"

And the other graphs are equally as silly- and obviously an ironic reference to graphs showing correlation between sunspots activity global temperature. Which obviously the author of the hoax sees as too perfect of a match to be credible [unlike the holy CO2 and temperature graphs which instead showing CO2 as cause of warming, it appears to the "unclean unchosen" to be an effect of warming- and little correlation in time spans of merely decades or centuries].

So, in order to have that kind of fun, he deliberately put in grossly obvious false facts, hoping the dummies or at least enough of them would take the bait [natural sources which do dwarf human emission].