* Australian students rally from Sydney to outback
* "The oceans are rising, and so are we", say protesters
* Activists in Thailand storm Environment Ministry
* Activist Greta Thunberg to spearhead global rallies
* Protests demand action ahead of U.N. climate summit
By Hans Lee and Patpicha Tanakasempipat
SYDNEY/BANGKOK, Sept 20 (Reuters) - Tens of thousands of students were taking to the streets across Asia and Europe on Friday for a global strike demanding world leaders gathering at a U.N. climate summit adopt urgent measures to avert an environmental catastrophe.
The protests kicked off in the Pacific islands - some of the nations most threatened by rising sea levels - and Australia, where social media posts showed huge demonstrations around the country, from the big coastal cities of Melbourne and Sydney to outback towns such as Alice Springs.
"The oceans are rising and so are we," read one sign held by a protester wearing school uniform in Melbourne. Another sign, carried by a student in Sydney, read: "We didn't light it, but we're trying to fight it."
Inspired by the 16-year-old Swedish activist Greta Thunberg, protests are planned in about 150 countries to call on governments to take immediate action to limit the harmful effects of manmade climate change.
The strike will culminate in New York when Thunberg, who has been nominated for a Nobel Peace Prize for her climate activism, will spearhead a rally at the United Nations headquarters.
Thunberg noted the "huge crowd" in Sydney in a tweet, which she said would set the standard as the strikes moved across Asia, Europe and Africa.
Danielle Porepilliasana, a Sydney high school student, had a blunt message for politicians such as Australian Finance Minister Mathias Cormann, who told parliament on Thursday that students should stay in class.
"World leaders from everywhere are telling us that students need to be at school doing work," she said, wearing anti-coal earrings. "I'd like to see them at their parliaments doing their jobs for once."
Global warming caused by heat-trapping greenhouse gases from burning fossil fuels has already led to droughts and heatwaves, melting glaciers, rising sea levels and floods, scientists say.
Carbon emissions climbed to a record high last year, despite a warning from the U.N.-backed Intergovernmental Panel on Climate Change in October that output of the gases must be slashed over the next 12 years to stabilise the climate.
Organisers said demonstrations would take different forms around the world, but all aim to promote awareness of climate change and demand political action to curb contributing factors.
The protest movement is putting increasing pressure on both governments and companies to respond.
Online retail giant Amazon.com Inc pledged on Thursday it would be net carbon neutral by 2040 and would buy 100,000 electric delivery vans from a start-up firm.
Cutting emissions is a challenging goal for Amazon, which delivers 10 billion items a year and has a massive transport and data centre footprint. "We know we can do it and we know we have to do it," Chief Executive Officer Jeff Bezos said.
Environmental advocacy group Greenpeace USA welcomed the commitment, but a spokesman said the company lagged peers Google, Apple and Facebook in transparency around its renewable projects.
Some of the company's workers from the group Amazon Employees for Climate Justice plan to join marches on Friday.
In Europe, German Chancellor Angela Merkel was due to unveil a major new climate protection package thrashed out by parties in her coalition in all-night talks. On the streets of Berlin, protesters were due to gather at the Brandenburg Gate.
The U.N. summit brings together world leaders to discuss climate change mitigation strategies, such as transitioning to renewable energy sources from fossil fuels.
The issue is vital to low-lying Pacific islands, which have repeatedly asked wealthier nations to do more to prevent rising sea levels.
As Friday's day of action got underway across scattered Pacific communities, students holding placards in Kiribati chanted: "We are not sinking, we are fighting". Children in the Solomon Islands rallied on the shoreline wearing traditional grass skirts and carrying wooden shields.
Hours later in Thailand, more than 200 young people stormed the Environment Ministry and dropped to the ground feigning death.
"This is what will happen if we don't stop climate change now," said 21-year-old strike organiser Nanticha Ocharoenchai.
In India's financial capital Mumbai, battered this year by a heavier-than-usual monsoon that caused flooding and frequent transport breakdowns, children from at least 10 schools joined protests throughout the day.
Children in the eastern city of Kolkata handed out flyers at busy bus terminals and held placards reading: "Save our Planet, Save Our World".
"This is the only planet we have. We wanted to stand for it before we went to school for the day," one of the children said.
No protests were authorised in China, the world's biggest source of greenhouse gas emissions, but Zheng Xiaowen of the China Youth Climate Action Network said Chinese youth would take action one way or another.
"Chinese youth have their own methods," she said. "We also pay attention to the climate and we are also thinking deeply, interacting, taking action, and so many people are very conscientious on this issue." (Reporting by Hans Lee in Sydney and Patpicha Tanakasempipat in Bangkok; additional reporting by David Stanway in Shanghai and Sonali Paul in Melbourne; Writing by Joanthan Barret, Stephen Coates and Alex Richardson; Editing by Lincoln Feast and Janet Lawrence)
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