SAN FRANCISCO (CBS SF) — Morning rush hour traffic came to a near halt in San Francisco’s South of Market neighborhood early Thursday as protesters representing a wide variety of environmental causes took to the city streets.

Hundreds of scientists, business leaders and political leaders have gathered in San Francisco for the three-day Global Climate Action Summit hosted by California Gov. Jerry Brown.

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Also in the city were several different environmental groups who were demanding action on a range of issues including offshore oil drilling, timber harvesting and oil pipelines built across Native American lands.

On Thursday, at least two of those groups chose to block streets and the entrance to Moscone Center — the site of the summit — turning the morning commute into a chaotic mess.

Nearly 500 chanting protesters blocked the intersections of 3rd and Howard St. and 3rd and Folsom St. under the watchful eye of a contingent of San Francisco police officers. Many of critical of what they call Brown’s slow response to the threat of increase oil drilling in California.

Inside the event, Brown and former New York Mayor Michael Bloomberg were holding a news conference.

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“America’s a wonderful country,” Bloomberg said. “Here we got environmentalists protesting at an environmental conference. It reminds me of people who want to build a wall along the Mexican border to keep people out from a country that we go to for vacations. Something is crazy here.”

Brown, meanwhile, took aim at President Donald Trump saying he will be remembered as a “liar, criminal, fool… take your choice.” He added big challenges were ahead to slow climate change.

“We are getting it done, but we have a very tall mountain to climb,” he said.

When it came to the protesters claims, Brown said he has on a multi-facet global climate plan that includes more than just limits on oil production.

“This is 10 points, 10 dimensions where we are looking. There is no one off here. There’s no one thing,” he said. “California with the leadership of our Air Resources Board has released a scoping plan that covers the whole range of emissions from oil to transportation to trucks to housing…So my plan is an integrated plan built up over time that is subject to review over time.”

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“Our goal is a 45 percent reduction in oil production as well as consumption,” he added. “We have the actual method of getting there.”