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San Francisco — Led by students, thousands of people around the Bay Area took to the streets Friday as part of a global “climate strike” to urge political leaders to do more to address climate change.

In San Francisco, a crowd estimated at roughly 8,000 people met at the federal building on Seventh Street, where House Speaker Nancy Pelosi and U.S. Sen. Dianne Feinstein have offices, and marched 1.1 miles down Market Street, past the offices of Bank of America and PG&E, before ending at Embarcadero Plaza near the Ferry Building.

Chanting and banging drums, the crowd, largely made up of young people, held signs saying “Grown-ups do something,” “There is no Planet B” and “Governor Newsom, stand up to big oil.”

In the East Bay, about 200 people gathered to chant and rally in the Laney College courtyard, including groups of students from Montclair Elementary and St. Paul’s Episcopal School in Oakland. Organizers planned to board BART and join marchers in San Francisco later in the day.

St. Paul’s eighth grader Lily Salazar, who came to the demonstration as part of a field trip with dozens of her classmates, said she wanted to send a message to politicians that, in the future, “We are going to be the voters” and that the changing climate matters to them.

“It’s our futures — if we don’t stand up now then eventually it will be too late,” Salazar said. “We’re going to have to live with it.”

On the Peninsula, students walked out of class at San Mateo High School and other high schools. And in San Jose, at least 1,000 people came together outside Diridon station Friday afternoon, then made their way to City Hall for speeches and other presentations.

Similar protests took place across the United States and in other countries, with events planned at 4,500 locations in 150 countries, from France to Uganda to Afghanistan, where 100 people, mostly young women, marched in Kabul holding signs and protected by armed soldiers. In Australia, an estimated 300,000 people demonstrated, according to the Associated Press. Huge crowds also marched in London, Berlin, Bankok, Paris, Warsaw and other cities. The events were timed around a United Nations Climate Summit set for Monday in New York.

The demonstrations were inspired by a series of school walkouts started by Greta Thunberg, a 16-year-old Swedish activist who this week testified before the House of Representatives — “Don’t invite us here to just tell us how inspiring we are without actually doing anything about it” she told the lawmakers — and met former President Barack Obama.

Although schools in New York City allowed students to take the day off as an excused absence if they marched, that wasn’t the case in the Bay Area. School districts around the region issued statements saying they generally supported the students’ exercising their First Amendment rights, but that anyone who left a school facility would be given an unexcused absence. Some noted that schools cannot protect students when they leave campus and that they would lose state funding for each student who missed a day of school.

Cynthia Greaves, communications manager for the Mountain View Los Altos School District, said Friday that although the district “supports the students’ civic rights to participate in the walkout, their absences will not be excused.”

It is up to each teacher’s discretion whether students who participate in the walkout will be able to make up the class work they miss, Greaves said.

Liv Wisely, 17, a senior at El Cerrito High School in Contra Costa County, said teachers agreed to excuse her absences so she could attend the demonstration Friday morning. She was motivated by a sense of responsibility to future generations, she said.

“There really is a right and a wrong side of history,” Wisely said. “In the end, you’re going to be held responsible, the same as everyone else who just stood by and watched it happen.”

They’re walking out of class right now at San Mateo High School for a climate protest. Students say they are demanding that the government take action against climate change. pic.twitter.com/Vtidmn5qbt — Amy Hollyfield (@amyhollyfield) September 20, 2019

Anna Fletcher, Los Altos High senior and an organizer of the school’s walkout, called Thunberg a “big inspiration” for the decision to plan a march.

“Some people think protesting doesn’t do anything, but it really only takes one person to make a change,” she said.

Climate Strike march in San Francisco — Isha Clarke, 16, of Oakland pic.twitter.com/RIGIyDlq3t — EthanBaron (@ethanbaron) September 20, 2019

Climate activism has been ramping up over the last two years as the effects of climate change have become more visible.

July was worldwide the hottest month recorded since 1880 when modern temperature records began. The 10 hottest years over that period all have occurred since 1998, according to NASA and NOAA.

Record heat waves have gripped Europe this summer. Hurricane Dorian battered the Bahamas and the East Coast, its category 5 peak strength driven in part by warmer-than-normal water temperatures. Large fires have charred millions of acres across Alaska and Siberia in recent months. And on Aug. 2, Greenland lost 12.5 billion tons of ice to melting, the largest single-day loss in recorded history.

Although a majority of Americans now say in surveys they are concerned about human-driven climate change and support policies to expand renewable energy such as solar and wind, concern over the issue is greater among younger people.

A Gallup poll conducted last year found that 70% of Americans age 18 to 34 say they worry about global warming, compared with 62% of Americans 35 to 54 and 56% who were 55 or older.

In the heart of Silicon Valley, about 50 students at Los Altos High School walked out of their classes around 10 a.m. and began a 1.5 mile march to the Mountain View City Hall. The students had created a list of environment-related demands for the Mountain View Los Altos School District and the Mountain View City Council. They included divestment from the fossil fuel industry, implementing “meatless Mondays” in school cafeterias, and ensuring that all new construction is all-electric by 2021.

Evelyn Sanchez, a senior currently taking an AP environmental science course, said she was marching Friday for her future.

“I know it may not seem like a lot of people and we’re just kids, but we can make a difference,” Sanchez said. “Especially in Silicon Valley, where we’re all about innovation and technology.”

In San Jose, Carolina Villa, a junior at Presentation High School who was volunteering as a safety ambassador for the Friday afternoon march, said she wanted to get involved as soon as she heard about the strike.

“Ever since about fourth grade, I’ve been interested in the environment,” Villa, sporting an orange safety vest and carrying a flag to lead the crowd, said. “But really, since hearing about the fires in the Amazon Rainforest, I knew I couldn’t just sit and wait around for something to happen.”

Young Afghan women lead climate change march in Kabul. @ap photo pic.twitter.com/cuwwM6uC36 — Borzou Daragahi 🖊🗒 (@borzou) September 20, 2019