Thousands of people descended on Washington and other cities across the country on Saturday to voice support for science, with calls for evidence-based public policy and increased funding for scientific research as President Trump defended his climate policies.

While the massive March for Science demonstration was officially organized to support evidence-based efforts in Washington, many marchers voiced opposition to Trump's administration, which they view as hostile toward the scientific community.

Under grey skies and chilly rain, thousands of people crowded onto the National Mall to hear from speakers, who urged policymakers to fund scientific research and pursue efforts to ease and reduce the effects of climate change.

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"Today we have a great many lawmakers, not just here, but around the world, deliberately ignoring and actively surpassing science," Bill Nye the "Science Guy" told marchers. "There inclination is misguided, and in no one’s best interest."

Some protesters on the National Mall waved signs embracing science-related puns, such as one featuring an image of Albert Einstein that stated "Science cuts make me relatively angry," a reference to the famous physicist's Theory of Relativity.

"Pretty absurd that this march is necessary," another sign read.

Anne, from Long Island, says the being with people at the #ScienceMarch reminds her that when you go on social media you're not alone pic.twitter.com/yEw9Sxs2kX — Sam Levine (@srl) April 22, 2017

The March for Science, which stretched to cities such as London and as far away as Antarctica, was the latest in a series of massive weekend protests linked to opposition to Trump and his policies.

A day after Trump took office on Jan. 20, hundreds of thousands of demonstrators took to the streets for the Women's March on Washington and related rallies, and crowds gathered earlier this month to protest Trump's decision not to release his tax returns.

The science march and its sister rallies across the country had been billed as a nonpartisan show of support for scientific enterprise, though a number of demonstrators voiced their opposition to Trump, who has called climate change a hoax created by China.

In Chicago, authorities estimated a crowd of more than 40,000. By noon, according to the city's NBC 5 News, police were telling would-be attendees who had not yet gotten to the march to avoid the event altogether.

In Los Angeles, billionaire Democratic donor and environmental activist Tom Steyer spoke to a crowd of thousands, taking direct aim at Trump. The Trump administration, he said, was bent on ignoring evidence of climate change in favor of corporate interests.

.@TomSteyer (who may run for Gov https://t.co/nHCEuK9BF3 ) delivers a very California centric speech at the LA #marchforscience (part 1) pic.twitter.com/SfjVMzfGi2 — Javier Panzar (@jpanzar) April 22, 2017

"There is a force in our land," Steyer said. "There is a force coming out of Washington, D.C., called the Trump administration that is out to deny truth and bury science."

Democratic lawmakers seized on the occasion to hit the Trump administration on what some claimed is an outright denial of scientific evidence and willful disregard of the scientific community.

"Science is real. Climate change is real. And the danger the Trump administration poses to the future of our environment & planet is real," Rep. Pete Aguilar (D-Calif.) wrote on Twitter.

"With an administration that deals in alternative facts, supporting objective science is more important than ever #MarchforScience#EarthDay," Sen. Mazie Hirono Mazie Keiko HironoDemocrats unveil plan declaring racism a public health issue Overnight Defense: US, Russia trade blame over Syria incident | Pentagon calls out China's 'counterproductive' military exercises, missile test | Democrats press Esper on COVID-19 response Democrats press Esper on 'concerning' rise in Pentagon's COVID-19 cases MORE (D-Hawaii) tweeted.

Trump defended his climate policies on Saturday, saying in a statement marking Earth Day that "rigorous science is critical" to his administration's work.

"Economic growth enhances environmental protection. We can and must protect our environment without harming America’s working families. That is why my Administration is reducing unnecessary burdens on American workers and American companies, while being mindful that our actions must also protect the environment," he said.