Wikipedia is little more than a propaganda source that allows interested, mostly left-leaning but certainly establishment-supporting parties to spread disinformation. And, it seems like one of those involved in Climategate may have been using Wikipedia to present biased coverage of global warming.

Actually looking into the details and specific edits is left as an exercise, but according to this:

[CRU scientists] turned to their friends in the media and to the blogosphere, creating a website called RealClimate.org [note: see this]... One person in the nine-member Realclimate.org team — U.K. scientist and Green Party activist William Connolley — would take on particularly crucial duties... Connolley took control of all things climate in the most used information source the world has ever known – Wikipedia. Starting in February 2003, just when opposition to the claims of the band members were beginning to gel, Connolley set to work on the Wikipedia site. He rewrote Wikipedia’s articles on global warming, on the greenhouse effect, on the instrumental temperature record, on the urban heat island, on climate models, on global cooling. On Feb. 14, he began to erase the Little Ice Age; on Aug.11, the Medieval Warm Period. In October, he turned his attention to the hockey stick graph. He rewrote articles on the politics of global warming and on the scientists who were skeptical of the band. Richard Lindzen and Fred Singer, two of the world’s most distinguished climate scientists, were among his early targets, followed by others that the band especially hated, such as Willie Soon and Sallie Baliunas of the Harvard-Smithsonian Center for Astrophysics, authorities on the Medieval Warm Period.

All told, Connolley created or rewrote 5,428 unique Wikipedia articles. His control over Wikipedia was greater still, however, through the role he obtained at Wikipedia as a website administrator, which allowed him to act with virtual impunity. When Connolley didn’t like the subject of a certain article, he removed it — more than 500 articles of various descriptions disappeared at his hand. When he disapproved of the arguments that others were making, he often had them barred — over 2,000 Wikipedia contributors who ran afoul of him found themselves blocked from making further contributions. Acolytes whose writing conformed to Connolley’s global warming views, in contrast, were rewarded with Wikipedia’s blessings. In these ways, Connolley turned Wikipedia into the missionary wing of the global warming movement.

He goes on to say that the "Medieval Warm Period disappeared", but that's not entirely clear. It may have been factored in to the "hockey stick graph" in some (perhaps dishonest) way, and the article on the MWP was in Wikipedia at least in 2007. Once again, looking into specific edits is left for those who are familiar with this topic, but those who are are strongly encouraged to do so in order to help further discredit Wikipedia.

Note also that Connolley was mentioned in the article "Know It All/Can Wikipedia conquer expertise?" by Stacy Schiff of the New Yorker, with Jimmy Wales taking Connolley's side (link):

For all its protocol, Wikipedia’s bureaucracy doesn’t necessarily favor truth. In March, 2005, William Connolley, a climate modeller at the British Antarctic Survey, in Cambridge, was briefly a victim of an edit war over the entry on global warming, to which he had contributed. After a particularly nasty confrontation with a skeptic, who had repeatedly watered down language pertaining to the greenhouse effect, the case went into arbitration. “User William M. Connolley strongly pushes his POV with systematic removal of any POV which does not match his own,” his accuser charged in a written deposition. “His views on climate science are singular and narrow.” A decision from the arbitration committee was three months in coming, after which Connolley was placed on a humiliating one-revert-a-day parole. The punishment was later revoked, and Connolley is now an admin, with two thousand pages on his watchlist—a feature that enables users to compile a list of entries and to be notified when changes are made to them. He says that Wikipedia’s entry on global warming may be the best page on the subject anywhere on the Web. Nevertheless, Wales admits that in this case the system failed. It can still seem as though the user who spends the most time on the site—or who yells the loudest—wins.

Connolley believes that Wikipedia “gives no privilege to those who know what they’re talking about,” a view that is echoed by many academics and former contributors...

That same New Yorker article has this appended:

The July 31, 2006, piece on Wikipedia, “Know It All,” by Stacy Schiff, contained an interview with a Wikipedia site administrator and contributor called Essjay, whose responsibilities included handling disagreements about the accuracy of the site’s articles and taking action against users who violate site policy. He was described in the piece as “a tenured professor of religion at a private university” with “a Ph.D. in theology and a degree in canon law.”

Essjay was recommended to Ms. Schiff as a source by a member of Wikipedia’s management team because of his respected position within the Wikipedia community. He was willing to describe his work as a Wikipedia administrator but would not identify himself other than by confirming the biographical details that appeared on his user page. At the time of publication, neither we nor Wikipedia knew Essjay’s real name. Essjay’s entire Wikipedia life was conducted with only a user name; anonymity is common for Wikipedia administrators and contributors, and he says that he feared personal retribution from those he had ruled against online. Essjay now says that his real name is Ryan Jordan, that he is twenty-four and holds no advanced degrees, and that he has never taught. He was recently hired by Wikia—a for-profit company affiliated with Wikipedia—as a “community manager”; he continues to hold his Wikipedia positions. He did not answer a message we sent to him; Jimmy Wales, the co-founder of Wikia and of Wikipedia, said of Essjay’s invented persona, “I regard it as a pseudonym and I don’t really have a problem with it.”