"thereby confirm" is correct and can be used in written English.
It is often used to indicate that one action or event has confirmed or verified something else. Example: By signing the contract, we thereby confirm our agreement to the terms and conditions.
We prostrate ourselves at love's portals, like social strivers waiting at the rope line outside some exclusive club hoping to gain admission and thereby confirm our essential worth.
Like national holidays commemorating common experiences, elections link citizens to each other and thereby confirm the viability of the polity.
Physicists are engaged in the biggest scientific experiment in the history of the world at CERN, the European particle physics laboratory, in an attempt to find the particles associated with this field and thereby confirm its existence.
When architecting dependable systems, in addition to improving system dependability by means of construction (fault-tolerant and redundant mechanisms, for instance), it is also important to evaluate, and thereby confirm, system dependability.
The term display is defined as 'the process by which individuals and groups of individuals, convey to each other and to relevant audiences that certain of their actions do constitute 'doing family things' and thereby confirm that these relationships are 'family' relationships' (Finch 2007, p. 67).
OK, yes, all the Google-smart news-speak mavens can choose to buy their fresh foods at the most expensive markets and thereby confirm their conspira-stories that healthy, local food is elitist.
His late, firm case for Ryder Cup inclusion was thereby confirmed.
And the rest of us are going to be your in-house" – thereby confirming what Fox New critics have consistently maintained about the network's faux-news agenda and its built-in ideological bias.
Almost every night I spent at the Table, there was a moment when I failed to enlighten the poets as to how music was written, thereby confirming their initial assumption that I was a lousy conductor, albeit a funny guy.
But that assumes that the Iraqi captive will now reveal weapons of mass destruction and his connections to Al Qaeda, thereby confirming the intelligence that the Bush neocons are charged with having cooked up to justify going to war.
When Burnside and Dollar included all the countries in their sample, regardless of the economic policies their governments pursued, they found no link at all between aid and growth, thereby confirming Peter Boone's negative findings.
