Real were cruising after Brazilians Kaka and Marcelo scored first-half goals and Gonzalo Higuain added a third on 64 minutes before Sergio Ramos was shown a straight red for a foul on Sergio Aguero.
Roared on by the home crowd, Diego Forlan pulled a goal back with 11 minutes of regular time left, Aguero added another three minutes later and Iker Casillas produced a superb save to deny the Argentina striker at the death as Real held firm.
"We had a very good first half and controlled the second until Ramos was sent off," the Chilean said.
"The final minutes were dangerous but did not reflect the superiority we enjoyed throughout the match as a whole."
The ploy seemed to be paying off when Zlatan Ibrahimovic released Pedro to slot home Barca's first in the 11th minute but they were rocked back nine minutes later when Jose Carlos Nunes headed in from a corner.
Pedro was again involved in Barca's third four minutes later, floating a freekick to the far post that Busquets nodded back across goal for Henry to head into the empty net.
"It was an ugly match," Guardiola told a news conference. "It can rain or be cold but wind is the worst. It wasn't one of our best matches but it wasn't bad either."
Mista nodded the visitors in front in the 15th minute before Miguel Angel Lotina's side went down to 10 men 12 minutes later when striker Riki was shown a second yellow card for what appeared from television replays to be an attempted hand ball. He was earlier booked for diving in the penalty ar
