Maine’s largest environmental advocacy organization is holding its fifth annual cold-water ocean plunge to raise money in the name of global warming. The Natural Resources Council of Maine is expecting about 200 people for its Polar Bear Plunge, held at noon Monday at Portland’s East End Beach. The event raises money and awareness for the group’s work on climate change issues. For those who aren’t up for a bone-numbing dip into the ocean, they can still raise money and take part in a 5-kilometer walk or run. Last year nearly 200 people took part, raising $18,000.