Philip E. Clapp, 54; Led Environmental Policy Group

Philip E. Clapp, 54, who created an environmental policy and advocacy group that is now part of the Pew Environment Group and who successfully agitated for environmental causes through jet-setting diplomacy and grass-roots mobilizing, died of pneumonia Sept. 17 at Spaarne Hospital while on vacation in Hoofddorp, Amsterdam. He was a District resident.

Mr. Clapp devoted his 32-year career in Washington to fighting global warming, preserving the world's oceans and reducing air and water pollution. A practicing Buddhist who was also a workaholic and a chain smoker, he focused much of his work on trying to fashion a international pact that would make significant cuts in greenhouse gases.

In 1994, he founded the National Environmental Trust, an environmental policy and advocacy group based in Washington and with operations in 20 states.

As president of the group, he initially focused on blocking congressional Republicans' attempts to roll back several environmental laws. He broadened the group's mission to mobilize grass-roots support for an array of green causes.

"In a community that's more policy wonk than political, Phil was the political one, always," said United Nations Foundation President Timothy E. Wirth, who hired Mr. Clapp at age 22 to work in his congressional office. "He was the single most effective person in terms of pushing for change and pushing people to actually do things."

"He was a master strategist and tactician, but he was a master strategist with X-ray vision," said Kevin Knobloch, president of the Union of Concerned Scientists. "When I say X-ray vision, he could see to the heart of a legislative logjam and come up with an elegant solution."

As a Capitol Hill staff member, Mr. Clapp challenged the chemical industry's impact on the environment and helped win reauthorization of the Clean Air Act in 1990.

At the National Environmental Trust, he lobbied successfully for the Safe Drinking Water Act amendments of 1996, which greatly strengthened the original law. He also had a role in the 2006 reauthorization of the Magnuson-Stevens Fishery Conservation and Management Act, which made scientific recommendations a greater priority in managing the nation's fisheries.

The National Environmental Trust and Pew Charitable Trusts merged in January to form the Pew Environment Group. Mr. Clapp, as deputy managing director, continued to focus primarily on energy and climate issues.

To help broker a global climate agreement, Mr. Clapp journeyed to international negotiations around the globe, cajoling heads of state and their deputies into pressing for more aggressive greenhouse gas reduction targets.

He pushed his allies and negotiating partners hard, but he sometimes eased tensions by regaling them with tales of royal misdeeds from hundreds of years ago.

"He knew every affair that every king and queen had, all of their illegitimate children, and was hilarious about it," Wirth said.

Philip Estabrook Clapp was born Nov. 13, 1953, in Los Angeles and graduated from Harvard University. As a teenager, he worked on Sen. Eugene McCarthy's (D-Minn.) unsuccessful 1968 presidential campaign.

Mr. Clapp started working on Capitol Hill in 1975 for Sen. John A. Durkin (D-N.H.) and stayed on for the next decade with Wirth and the House Banking Committee.

After leaving Capitol Hill, he worked with a major investment banking firm on mergers and acquisitions and represented labor unions in large corporate transactions.

Survivors include his mother, Vivian Clapp of Los Angeles, and a sister.