Adverbial clauses are dependent clauses used to modify verbs, adjectives, adverbs, or entire phrases or clauses. They are introduced by subordinating conjunctions. As introductory elements, they may begin a sentence; they may also be placed in the middle or at the end of a sentence.
In September 1993 the U.S. auto industry and the Clinton administration
announced a historic partnership to develop vehicles having three times the fuel
economy of today's fleet while they provide the same comfort, safety and
performance.
--"Improving Automotive Efficiency," Scientific American(modified)
Never use a future tense marker (will or going to) in an adverbial clause.
If observations will tell us that the density of the
universe is considerably different from the critical density, which corresponds
to a flat universe, inflationary cosmology will face a real challenge.
If observations tell us that the density of the universe
is considerably different from the critical density, which corresponds to a flat
universe, inflationary cosmology will face a real challenge.
--"The Self-Reproducing Inflationary Universe," Scientific American