SAN FRANCISCO, Sept. 13 (Xinhua) -- The Global Climate Action Summit, which brings delegates from city and regional governments, industries and research institutions to western U.S. city of San Francisco to enhance cooperation in tackling climate change, officially opened on Thursday.

At the opening plenary, San Francisco Mayor London Breed called on cities around the world to join hands and address the climate change as she welcomed more than 4,000 delegates from six continents for the summit.

Xie Zhenhua, special representative for climate change affairs of China, said at the plenary that China has made the fight against climate change a major strategy of its economic and social development.

China's gross domestic product grew 1.5 times between 2005 and 2017, but its carbon emissions have fallen by 46 percent, which reached in advance the goal of cutting by 40 percent to 45 percent carbon emissions by the year 2020, Xie said.

He added that the country invested 126.7 billion U.S. dollars to develop renewable energy, marking the sixth consecutive year in which China invested the most globally as a nation in renewable energy.

China's efforts in flighting climate change was acknowledged by many speakers at the summit.

"China's leadership has been truly outstanding. I want to repeat the gratitude people around the world feel for China," said Al Gore, former vice president of the United States, at the China Pavilion, an affiliate event of the summit.

He said it is high time that countries step up financing clean energy and phase out subsidies of fossil fuels as consequences of climate crisis such as increasing occurrence of major storms are beginning to awaken people all over the world.

"It is significant that China is also the global leader in financing renewable energy," he said.

Challenging people, communities, societies and economies around the world to "step up," the summit is focused on taking ambition to the next level across five key issue areas: Healthy Energy Systems, Inclusive Economic Growth, Sustainable Communities, Land and Ocean Stewardship, and Transformative Climate Investments.

The three-day gathering features more than 25 sessions, 325 affiliate events and 500 major climate commitments.