Ken may repeat it because he has the same misunderstanding as you do...that repeating something many times will change people's minds.
I don't do it to change the minds of deniers, Inky. Denialists of all stripes are on record saying "No amount of evidence will change our mind". GW deniers, HIV causes AIDs deniers, Holocaust deniers, vaccines=autism proponents, birthers, moon landing deniers, are all unreachable. They have an ideological point of view, and anything that threatens that ideological view is rejected regardless of the amount of evidence.
I do it because the denialists have truly muddied the waters with falsehoods. I do it for the people who are open-minded and aren't sure what to believe. The denialists recycle the same arguments over and over again as if they've never been proven false years ago. Some claims are so ridiculous you don't even need specialized knowledge to refute it. Others can be refuted with a Grade 7/8 level of math.
Their arguments are distortions, cherry-picks, strawmen, misquotes of real scientists, and things they just make up. None of it stands up to any scrutiny; most of it insults the intelligence of their readers. As I've said before some of the strongest evidence for GW comes from the paucity of the denialist arguments.
Their goal, though, is not to dispute global warming on scientific terms, but to create the image that science is still divided and unsure. They want to create paralysis, prevent action. For some they do that because their political ideology is "less gov't, the better", and when confronted with a problem so huge that more gov't will be needed, they reject the evidence, deny it exists, make things up, simply because of a political ideology. Others are tied to oil companies who have been actively funding think tanks and some individuals...essentially paying them to lie.
I have never seen so many scientists taking to the message boards to condemn the deniers who take their papers, misquote them to make them say the opposite of what the author(s) said. They are furious at the deliberate misinterpretation of their work. I have never seen so many deliberate lies by people who do know better, not even with the whole acid rain thing back when Reagan was denying there was a problem (same people involved in that denial campaign are in the GW denial campaign...and tobacco smoke health risk denial campaign).
And I don't just repeat things. I usually back it with evidence from real scientists, real experts, people who work in the field of climatology. I've only seen two denialist arguments that were good...and the people making them at the time were true skeptics, not denialists. Since then both points have been accounted for.
One was because a satellite orbit had decayed and it was measuring temp at a different time than ground stations thought---that was a problem because climate models predicted one thing, yet the satellite data said the opposite. Then in 2005 they found the satellite had drifted, and once that was taken into account, the satellite data now matched the climate models very nicely. So the strongest argument against turned out to be a strong argument for....so if you see a denier talking point saying, "Satellite temps do not show warming in the upper atmosphere", they are now lying...and I say lying because they would have heard the explanation many times now.
Other falsehoods are: warming stopped in 1998 (or 2002), ocean temps are not increasing, sea levels aren't rising, 555 of the 625 monitored glaciers are growing (or 55% of glaciers are growing)--regardless, both points are just made up, its all from the sun, its the urban heat island effect, CO2 isn't a greenhouse gas, etc etc etc ad nasuem.
If anyone is tempted to write a contrarian comment on a science blog, first do some independent reading... (as CF clearly has been doing since he's beginning to agree with the science now...stop apologizing too, CF, we know your opinion was uninformed and therefore useless but you're now remedying that and doing some reading so you have a better idea what you're talking about...the old CF is dead, the new CF has learned to read)
... because if you post one of these falsehoods and declare "explain this!", you'll be shredded, given some basic links to read, and told to come back when you've read them and know what you're talking about. They're happy to educate, but if they suspect you're not educatable, they'll leave you a gooey humilated mess. Yeah, some scientists are a-holes...doesn't mean they are wrong though (google that, btw, Orac just had a post about a-hole scientists...good reading).
Science folks have heard the same lies thousands of times now and their patience is getting short with people who refuse to learn (I just read a report by either NASA or national academy of sciences, and one of their main bullet points is "Anyone who thinks GW is not happening, has their head in the sand". Pretty blunt for scientists, but they're tired of the same lies, tired of being told they're the liars who are hoaxing the public, that they're part of some big conspiracy, and they're tired of no-nothings Senators who are trying to get them fired simply because the Senators don't like the evidence these scientists find).