Pope Francis waving to the crowds (Vatican News).

Half a million young people chanted, cheered and shouted on Thursday as they packed a Lisbon park to give Pope Francis a rock star welcome at the official opening ceremony of a global Catholic youth festival.

“I am pleased to see all of you, and also to hear the delightful noise you are making! This makes me share your infectious joy,” the Argentine pope told the crowd in his native Spanish.

Pilgrims shrieked and waved as the 86-year-old pontiff, surrounded by bodyguards, slowly drove by on his popemobile through the 26-hectare (64-acres) hillside Eduardo VII park.

“We are the pope’s youths!” they chanted as flags of national groups from Canada, Brazil, Latvia, Mexico, Spain, and other countries fluttered around them.

Local authorities put the crowd size at 500,000.

The ceremony featured dance and song performances, including one by Portuguese fado star Mariza, a willowy singer with bleached blonde hair, who got a smile and a thumbs-up from the pontiff at the end of her set.

Many pilgrims had waited for hours under a blazing sun to get a view of the pope, singing and dancing to pass the time.

“It’s very impressive. It’s intense! The atmosphere is great!” said Geoffroy Garcia-Benito, a 17-year-old student from Angers in western France as he held a French flag.

It marked the pope’s first mass event with participants at this year’s World Youth Day, which is actually a six-day international Catholic jamboree.

The pope arrived in the Portuguese capital on Wednesday, when he met with the clergy and victims of clerical sexual abuse.

– Environmental plea –

Earlier on Thursday the pope urged young people to combine fighting to save the planet with tackling poverty during an address to students at Lisbon’s Catholic University.

“We must recognise the dramatic and urgent need to care for our common home,” he said, speaking in his native Spanish. “Yet this cannot be done without a real change of heart.”

“We cannot be satisfied with mere palliative measures or timid and ambiguous compromises,” added the pope, who has made the protection of the environment a cornerstone of his pontificate.

After his speech, the pope headed to Cascais, a seaside town some 30 kilometres (20 miles) west of Lisbon, to visit the local branch of his Scholas Occurrentes foundation, a movement he founded in 2013 to bring young people from different backgrounds and nationalities together.

There he answered questions from youths before putting the final brushstroke on a mural that the community has been working on.

“This is your Sistine Chapel,” the pope said, sparking laughter from the assembled youths.

Before leaving, the pope watered an olive tree, the symbol of peace, in the patio of the foundation.

– ‘Warm atmosphere’ –

Francis began his day meeting 15 young people from Ukraine at the Holy See’s diplomatic mission in Lisbon where he is staying, the Vatican said in a brief statement.

“After listening to their moving stories, he addressed a few words to the young people,” it added.

The meeting had not been listed on the official programme of the pope’s visit.

Organisers expect a million people from all over the world for the week of festive, cultural, and spiritual events.

“What strikes me the most is the warm atmosphere between people, everyone is ready to share, to party even with strangers,” said Paolo Lotini, a 17-year-old from Italy.

“The energy transmitted between different nationalities is incredible,” he added.

Francis will deliver a Mass on Sunday in Lisbon on the last day of his five-day visit to Portugal when temperatures are forecast to soar to 37 degrees Celsius (98.6 Fahrenheit).

World Youth Day, created in 1986 by John Paul II, is the largest Catholic gathering in the world and will feature a wide range of events, including concerts and prayer sessions.

This edition, initially scheduled for August 2022 but postponed because of the pandemic, will be the fourth for Francis after Rio de Janeiro in 2013, Krakow in 2016 and Panama in 2019.