Very Likely vs. Virtually Certain
That's the language argument over the new climate report as to how sure scientists are that humans are responsible for global warming. You can read the report here.

Here's what the LATimes says:

In the strongest language it has ever used, a United Nations panel says global warming is "very likely" caused by human activities and has become a runaway train that cannot be stopped.
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The phrase "very likely" indicates a 90% certainty. The last IPCC report, issued five years ago, said it was "likely" that human activity was at fault, indicating a certainty of 66%.

Many scientists had argued during the editing process that the report should say it is "virtually certain" that human activities are causing global warming. That would indicate a 99% certainty.

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The report also says scientists' "best estimate" is that temperatures will rise 3.2 to 7.8 degrees by 2100. In contrast, the increase from 1901 to 2005 was 1.2 degrees.

The report also projects that sea levels could rise by 7 to 23 inches by the end of the century, and perhaps an additional 4 to 8 inches if the recent melting of the Greenland ice sheet and the Larsen B ice shelf in western Antarctica continues at current rates.