Learn Spanish (Latin America): El náufrago empezó a escalar la palmera ayer. - The castaway started to climb the palm tree yesterday.

The hacía... que structure is used to express how long an action had been going on in the past (e.g., "He had been climbing for two hours"). In this sentence, the action of starting (empezó) is a single, completed event that happened ayer (yesterday). Because it is a discrete event rather than an ongoing background action, it uses the standard preterite tense.

Why is there an a between empezó and escalar?

In Spanish, verbs that indicate the beginning of an action require the preposition a before an infinitive verb. It is a set formula you have to memorize: empezar a + [infinitive].

Could I use comenzó instead of empezó in this sentence?

Yes, comenzó is perfectly interchangeable with empezó here. Both mean "started" or "began," and both require the preposition a before the infinitive. Comenzar can sound slightly more formal in some regions, but both are extremely common.

I know palma means palm. What is the difference between palma and palmera?