California Gov. Jerry Brown (D) joined the organization responsible for the Doomsday Clock as executive chairman, the group announced Thursday.

The Bulletin of Atomic Scientists said that Brown, who is retiring after his current term, will work with the leaders of its boards dedicated to governing, science and security.

The organization is focused on addressing man-made threats to the planet, such as climate change and nuclear war.

"I am honored to be stepping into this important role, particularly at this moment in time, when the Bulletin’s unique voice and depth of expertise is so clearly needed," Brown said in a statement from the organization.

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"Huge investments in new weapons systems, the growing existential threat of climate change, and a general antipathy toward evidence-based policymaking are putting all of us at grave risk," he added.

Brown, who served two terms as governor from 1975-1983 and two more from 2011 until the present, has signed a number of environmentally friendly laws in recent years while emerging as a national leader in efforts to counteract climate change.

The governor earlier this year signed a measure aimed at limiting the use of plastic straws, and a separate law committing the state to achieving a 100 percent renewable energy power grid by 2045.

Rachel Bronson, the president of the Bulletin of Atomic Scientists, told The Associated Press that the organization views Brown as a "global ambassador" for the group's cause.

The group created the Doomsday Clock in 1945, after the creation of the atomic bomb, as a visual symbol for the planet's health and safety. The closer the clock ticks to midnight, the more imperiled humanity and the planet is believed to be.

The Bulletin shifted the clock to two minutes from midnight at the start of 2018, citing flaring tensions between President Trump Donald John TrumpBiden says voters should choose who nominates Supreme Court justice Trump, Biden will not shake hands at first debate due to COVID-19 Pelosi: Trump Supreme Court pick 'threatens' Affordable Care Act MORE and Kim Jong Un as an example of a growing nuclear threat.

Trump and Kim met in Singapore in June, and the two countries have in recent months engaged in talks about the denuclearization of the Korean peninsula.

The Trump administration has said it is confident Kim will follow through in his pledge to abandon his nuclear arsenal, but the North has yet to take concrete steps to do so.