LONDON — Roughly two weeks into his job, the chief executive of Royal Dutch Shell warned on Friday that the oil company’s fourth-quarter results would be lower than financial markets had anticipated.

“Our 2013 performance was not what I expect from Shell,” the executive, Ben van Beurden, said in a statement as the company announced that adjusted earnings for the quarter would shrink to $2.9 billion, a 48 percent decline compared with the period a year earlier. Shell, which is based in The Hague, blamed the poor performance on weak industry conditions in refining, higher exploration expenses and lower production of oil and natural gas.

“We’re a bit shellshocked this morning after this profit warning, which is highly unusual for an integrated oil company,” analysts at Sanford C. Bernstein in London wrote in a research note.

Analysts had expected $4.9 billion in adjusted earnings for the quarter, according to Bloomberg News. Shell also took a $700 million impairment write-down.