It's not like the IPCC was trying to hide this. If anything, the entire way this scenario played out should be a reassurance that the IPCC and cooperating scientists are acting in good faith. They're not trying to "cover up" failures; they're acting on the established scientific process.
Actually, the linked research came from a survey commissioned by the WMO, not the IPCC...the IPCC fabricated the original claims that there would be more and more severe hurricanes due to global warming, according to the original article, with "no science so [sic] substantiate them."
One of the authors of this research, who resigned from the IPCC in protest over the original hurricane claim, indicated in 2005, "All previous and current research in the area of hurricane variability has shown no reliable, long-term trend up in the frequency or intensity of tropical cyclones." It has taken the past several years to compile data to change this stance, and the results contra-indicate the IPCC's original claims.
There are, undoubtedly, scientists who act largely in good faith based upon the existing climate data; the limited amount of data that I have seen indicates that there are aspects of global climate change that are quite real. The IPCC, however, is a political organization that appears transparently to be acting (or, at least, to have acted) in bad faith--between its baseless claims regarding hurricanes, its inaccurate estimates and later denial of the rate of melt of glaciers in the Himalayas, and various dubious data practices (failure of some members to comply with freedom of information requests, "lost" data and storing only reduced results of data, and selectively ignoring the tree ring data, to name just a few examples).
This is not the story of a claim being well-founded, but being corrected by advances in data or theory. This is the result of a political claim based on little or no evidence being examined by an outside body and found inaccurate.