Also see 350.org (Nonprofit)
350 Action is the 501(c)(4) “social welfare” advocacy affiliate of 350.org, an organization which seeks to radically reduce carbon emissions by eliminating the use of fossil fuels.  350 Action works to elect left-of-center politicians who will prevent the development of coal, oil, and natural gas resources through candidate endorsements and independent expenditures on behalf of those candidates.
350 Action and 350.org function almost seamlessly, sharing several board members and staff. A 2018 job posting for a “Voter Engagement Manager” specifically states that the hire would work “at both 350.org, a 501(c)(3) organization and 350 Action, a 501(c)(4) organization” managing the get-out-the-vote efforts on behalf of candidates that support the agendas of 350 Action and 350.org.
350 Action does not disclose the vast majority of its donors.
350 Action began as 1Sky Action, the 501(c)(4) political arm of 1Sky, in 2008. It was renamed 350 Action in when 1Sky merged with 350.org in 2011.
350.org is an environmental organization with the goal of ending climate change by replacing coal, oil, and gas with environmentalist-backed energy sources such as wind and solar. As 350.org’s associated 501(c)(4), 350 Action supports efforts to elect elect politicians who will enact legislation which requires that the United States use clean energy sources and stop using fossil fuels.
350 Action endorses candidates for public office, almost exclusively Democrats. In 2013, it endorsed then-U.S. Representative Ed Markey (D-Massachusetts) for the U.S. Senate for opposing the Keystone XL pipeline. In 2014, it endorsed Democratic candidate Rick Weiland for U.S. Senate from South Dakota. In 2016, it endorsed Democratic nominee Hillary Clinton for President. In 2017, it endorsed former U.S. Representative, Obama administration official, and left-wing nonprofit officer Tom Perriello (D) for governor of Virginia and left-wing U.S. Rep. Keith Ellison (D-Minnesota) for chairman of the Democratic National Committee. 
350 Action makes independent expenditures supporting or opposing candidates. In the 2014 election cycle, it spent $55,593 supporting then-Rep. Markey, $6682 supporting Weiland, and $228 opposing U.S. Rep. Fred Upton (R-Michigan). In 2016, it spent $90,042 opposing Republican Donald Trump and $5000 supporting Clinton.
2016 Presidential Election
350 Action’s support for Clinton was qualified. During the primaries, a 350 Action spokesperson challenged Clinton’s claim that she did not take any money from fossil fuel companies. Once Clinton secured the nomination, 350 Action supported her despite her ties to large businesses. 350 Action helped produce a video showing Sanders campaigning to get young voters out to support Clinton.
350 Action partnered with liberal magazine The Nation during the primaries to urge all candidates to sign a pledge not to take any campaign donations from fossil fuel companies.  Green Party nominee Jill Stein, former Maryland Governor Martin O’Malley (D), and U.S. Senator Bernie Sanders (I-Vermont) signed the pledge; neither Hillary Clinton nor any of the Republican candidates responded.
2018 Midterm Elections
In 2018, 350 Action continued its electoral activities. It endorsed several candidates for Congress as well as for governorships of several states, including Cynthia Nixon (D) for governor of New York. Endorsed candidates filled out a questionnaire about their positions and policies on environmental and left-wing “social justice” issues. The questionnaire also secured a pledge to refuse campaign contributions from traditional energy interests.
350 Action instituted a plan to get out the vote from environmentalists for the 2018 midterm elections. A job posting for a 350 Action Voter Engagement Manager said the hire would turn out what 350 Action claims are “millions of people in the United States who care about climate change but aren’t making it to the ballot box.”
350 Action is affiliated very closely with 350.org. K. C. Golden, Bill McKibben, and Jessy Tolkan are on the boards of directors of both 350 Action and 350.org.  The two organizations also share 13 staff members who hold the same or similar titles in each organization, including Executive Director May Boeve. 
Both organizations are involved in a Get-Out-the-Climate-Vote effort, which favors the candidates 350 Action has endorsed. In an advertisement for a Voter Engagement Manager to work for both 350.org and 350 Action, the groups list “Knowledge of legal limits on 501(c)(3) and 501(c)(4) affiliated organizations” as one of the “Desired (but not required) skills and experiences.”
It also supports specific “climate-friendly” legislation. In 2017, 350 Action supported a Congressional Progressive Caucus proposal to spend $2 trillion over ten years fixing schools, and other national infrastructure while moving America to a traditional-energy-free future.
Letter Encouraging U.S. to “Cooperate” with China
On July 7, 2021, 350Action along with 47 other organizations signed a letter to President Biden and the U.S. Congress accusing the United States of approaching China with “an antagonistic posture.”  The letter claims that “escalating, bipartisan anti-China rhetoric … bolsters racist, right-wing movements in the United States,” and that the “U.S. demonization of China has always been a major barrier to progress in global climate talks.”  The letter urges the United States to cooperate with the Chinese government, despite its record of humans rights abuses, to “address the existential threat that is the climate crises.” The letter also cites statistics on U.S. and Chinese greenhouse gas emissions and criticizes the U.S. for being “the biggest carbon polluter in history.” 
Environmentalist writer Bill McKibben is the on the board of directors of 350 Action. He is also listed as senior advisor and co-founder of 350.org. He is a long-time environmental activist who is said to have first brought the attention of the general public to the issue of global warming with his book The End of Nature.
In fiscal year 2015, 350 Action recorded revenue of $397,716.