It was a response to what he perceived as "hostile rhetoric" toward the EPA by the Trump administration and was his way of saying his voice on the board had been silenced, Richardson clarified. 

"It probably wasn't the most dignified phrase to use on Twitter, obviously I was being a bit sarcastic and provocative," Richardson said. "It was a bit of a sarcastic way of saying 'this is another action by this administration to deny science, to deny the facts and projections about climate change and to silence the voice of independent scientists in giving advice to the agency.'"   

The board advises the EPA's Office of Research and Development by reviewing scientific "outputs" such as peer-reviewed journals, and providing recommendations on research strategy, Richardson said.

Richardson was a member of this board for three years and was notified on Friday, May 5 his position would not be renewed. He said the move was unexpected and the non-renewed members were previously told they were going to be kept on.

"We met as an executive committee of the board in January in person," Richardson said. 

"We were informed at that time that nine of us were approaching the end of our first three-year term and were eligible for renewal to a second three-year term, and that they were putting in the paperwork to request that renewal to take place. And then, to our surprise, on (May 5) we all received notification by email that our positions would not be renewed." 

Richardson said he was disappointed by the non-renewal.

"I really enjoyed the work that I did as a member of this board, I felt like it was important work, I believe that the EPA took our advice and recommendations seriously," Richardson said.

EPA spokesman J.P. Freire told the Washington Post the last administration’s employees would not be “rubber-stamped” and that they should compete with the rest of the applicant pool, making “a clean break with the last administration’s approach.” 

Richardson said the EPA response angered him by appearing political, as he believes their work is impartial.

"As an independent science advisory board, we are not associated with an administration, we are independent, external scientists, many who had served under different administrations," Richardson said. "We were not a part of the Obama administration." 

Richardson said he was also disturbed by suggestions by Freire the open positions might be filled by industry-related appointees. 

"That (comment) bothered me because this board has no responsibility for regulations, (it) just reviews and gives feedback on science, so it has no role in reviewing, approving or considering regulations," Richardson said. "Those statements represented a fundamental misunderstanding of what this board does, and seemed very politically motivated." 

While Richardson said recent EPA actions concern him regarding the U.S.'s role in combating climate change in the near future, his long-term view on the issue remains optimistic.

"While other countries have taken significant strides to reduce the emissions of greenhouse gasses, to respond to the urgent need to do something about climate change, the United States has done nothing," Richardson said. 

"In the long run, the climate will continue to change and it doesn't really care what the president believes or not, or what EPA Administrator Scott Pruitt believes or not."