Christa Owens, a 2008 graduate of Mt. Lebanon High School, has been in Copenhagen for the past two weeks, in the midst of the international debate about how best to address climate change.

But Ms. Owens calls herself an "unlikely environmentalist."

She was not interested in environmental issues in high school, but during her first year as a student at Carleton College in Northfield, Minn., she took a seminar on environmental justice, and her interest was piqued.

Then she took a biology class on climate change and joined environmental campaigns and organizations, immersing herself in the issue of climate change at school and during the summer. Earlier this year, the Carleton sophomore heard that the Sierra Student Coalition, the high school and college chapter of the national environmental organization, was sending students to Copenhagen for the climate talks.

She applied and was accepted. In the weeks leading up to the December summit, she made conference calls with other delegates from around the country and did fundraising for the trip and research into climate issues.

Ms. Owens arrived Dec. 4 in Copenhagen for the start of the conference with an 18-person youth delegation. The presence of young people at the conference has been significant, she said, and reflects her hope that their presence is "highlighting the need for action."

In Copenhagen, she has been attending meetings, taking pictures and blogging on the Web site of the Sierra Student Coalition's international delegates page, http://sscinternational.org/.

She used Skype to call the Pittsburgh Post-Gazette last week, and said some of the most eye-opening parts of the summit have been her conversations with students from developing countries. People from Zimbabwe told her about how climate change can lead to famine in their country, she said.

"Hearing that and not just reading that in a report really humanizes climate change and reminds us what we are fighting for," she said.

In an e-mail update this week, she said on one evening she joined 50 other American and 30 Chinese students for a workshop on the future and climate strategy, and on Saturday, she marched with thousands of people to the site of the conference for a candlelight vigil.

"Our message is that we want a strong, ambitious and equitable treaty," she said.

Ms. Owens and the other members of her delegation will remain in Copenhagen until the conclusion of the meetings and return Saturday to the United States.

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