Greta Thunberg arrives in Europe for climate summit in Madrid

Climate activist Greta Thunberg says she feels "energized" after spending three weeks crossing the Atlantic in a catamaran, arrivingTuesday in the Portuguese capital of Lisbon en route to the UN Climate Change Conference in Madrid.

Thunberg told dozens of reporters and activists under bright sunshine on a Lisbon quayside that she plans to keep pressing political leaders to make climate change their top priority.

She wants senior officials in Madrid to "finally understand the urgency" of climate change and co-operate internationally.

Thunberg says: "People are underestimating the force of angry kids."

She saidshe travelled by catamaran instead of plane to "send a message it is possible" to live a sustainable lifestyle.

Activists stop traffic

In a protest Tuesday morning, the second day of the climate conference, some 20 activists cut off traffic in central Madrid and staged a brief theatrical performance to protest climate change.

Members of the international group Extinction Rebellion held up a banner in Russian that read: "Climate Crisis. To speak the truth. To take action immediately."

Some activists jumped into a nearby fountainwhile others threw them life-jackets. "What do we want? Climate justice," activists chanted.

Others dressed in red robes with their faces whitened to symbolize the human species' peril danced briefly before police moved in to end the protest.