Nine separate investigations found that climate scientists involved in the “climategate” controversy did not falsify data.
In 2009, the Climatic Research Unit’s servers were hacked. One scientist was reported as saying that he “completed Mike’s nature trick” to “hide the decline” in an email. The “trick” in question simply refers to combining instrumental temperature data and tree ring data.
“Hide the decline” referred not to a temperature decline, but a decline in the reliability of some tree rings as a temperature proxy. This had become an issue in data starting from the year 1960. Also known as the "divergence problem," it had been discussed in the scientific literature since the mid 1990s — 15 years before "climategate."
Steve Mosher, who fueled the conspiracy theory, has since issued a public apology, acknowledging that the scientists’ work was accurate.