It is with a heavy heart that I write this remembrance of my former boss, Virginia Senator John Warner, who passed away peacefully on May 26th.

I still recall the day in May 2007 (how was that 14 years ago?) when I was working for the National Wildlife Federation. I had been asked to join an environmental group meeting in Senator Warner’s office with his longtime environmental aid and legislative director, Ann Loomis. A team of Clean Water Act experts was scheduled to speak to her about the Waters of the U.S., and given I knew Ann, they’d asked me to tag along.

But my day got away from me and I decided four people was enough in the meeting and I opted not to go. As the meeting time approached, one of my colleagues walked by my office, noted I wasn’t on the Hill, and gasped, “but they need you.” I reluctantly hopped in a taxi and got to the Russell Senate Office Building just in time for the meeting to start. After we made the pitch, as the others dispersed, Ann and I were catching up via a walk and talk when she announced she was leaving Warner’s office after twenty-plus years. “You should take my job,” she said, part in jest.

I stopped in my tracks. “Are you serious?”

“Would you seriously consider it?” she responded.

By the time I got back to my desk, I already had a voicemail from her arranging an interview. Three days later, I had a job offer and had to tell Adam Kolton that I was leaving the Federation. (I’m really feeling the recent loss of Adam, knowing he’d have been one of the first to call and offer condolences. He was good at that kind of thing.)

I had no idea that three weeks after I started, Senator Warner would agree to co-author a climate change bill with Senator Joe Lieberman. Six weeks after I started, we released an “annotated table of contents” based on a set of shared principles the two hashed out. In June of 2008, one year after I had started working for him, we were on the Senate floor with the first (and only) economy-wide climate change bill passed out of committee.

Much will be written about Senator Warner’s Armed Services expertise. As a former Secretary of Navy and chairman of the Senate Armed Services Committee, that was his bailiwick. But he was also a committed conservationist and longtime member of the Senate Environment and Public Works Committee. Even though we knew our bill would not get the 60 votes necessary, he never let me talk as if the bill was going to fail. He called our efforts “laying a beachhead” and I’m sad that we didn’t make more progress in the 15 years that have passed since he got engaged in the fight for federal climate change action.

There are people who worked for him longer. (His staff retention was through the roof, actually, a testament to what a great boss he was.) There are people who knew him better. But his impact on my life and career cannot be overstated. With his passing, America lost a true public servant and a giant. I lost a truly great mentor.