As the world's warmest winter on record drew to an end with a weekend snow storm, a group of religious leaders started walking across the state Friday to bring attention to global warming.

"People have been asking me what happens if it snows," said the Rev. Fred Small of the First Church Unitarian in Littleton. "I tell them: 'We walk.' "

The nine-day haul from downtown Northampton, Mass., to Copley Square in Boston was planned far before forecasts called for a weekend of snow and sleet just a few days before the start of spring.

"It was windy and cold. I was walking on the front of the line and I felt like I was bow of a ship with the wind just coming into my face," said the Rev. Margaret Bullitt-Johns of the Grace Episcopal Church in Amherst, where the group warmed up on bowls of lentil and minestrone soup after walking eight miles in deep snow from Northampton to Amherst.

Bullitt-Johns said the walkers kept their spirits strong by singing "Keep on walking forward, never turning back," a hymn they had chanted in prayer services before the march to Boston.

The Rev. Andrea Ayvazian of the Haydenville Congregational Church said the snow was so deep, it felt like she was breaking trail.

In all 24 clergymen will walk the entire distance from Northampton to Boston, while some 800 people will join for smaller portions. The group hopes to have more than 1,000 gather in Boston for a final rally.

The National Oceanic and Atmospheric Administration reported Thursday that in the past century, global temperatures have increased at about 0.11 degrees per decade. But that increase has been three times larger since 1976.

The report comes just over a month after the Intergovernmental Panel on Climate Change said global warming is very likely caused by human actions and is so severe it will continue for centuries.

"God has given us this Eden, and our behavior is making a mess of it," said the Rev. Jim Antal, president of the Massachusetts Conference of the United Church of Christ, the state's largest Protestant denomination.

The religious walkers are part of Religious Witness for the Earth, a 6-year-old national interfaith environmental organization. Supporters include clergy from the Catholic, Unitarian, Jewish, Episcopalian and Muslim faiths.

The leaders are calling for individuals, businesses and government entities to reduce fossil fuel emissions by 80 percent by 2050.

With most of its members based in the Northeast, it made sense for the group to walk in Massachusetts. About 1,000 clergy members are expected to take some part in the trek, which will include prayer and information sessions along the way before ending with a rally March 24.

Not all the walkers are expected to make the entire journey. But synagogues and churches on their route will feed and shelter the multi-day hikers.

Many members of Religious Witness for the Earth have used their position from the pulpit to make their congregations aware of climate change.

"The interfaith aspect of what we're doing heightens awareness among everyone," said Rabbi Justin David of Congregation B'Nai Israel in Northampton. "Climate change is a moral issue and it's a collective issue. It transcends the differences of faith and politics and generations. This is something everyone needs to pay attention to."