In recent years, we've seen an increase in the intensity of tropical storms and hurricanes due to global warming. But how and why do hurricanes form? Sigrid provides a basic explanation of this phenomenon.

We continue to explore the phenomenon of hurricanes. Why are they so dangerous? And do they serve any purpose?

Wild dolphins playing with a plastic bag and a camerawoman. A video by the Wild Dolphin Foundation.

There's been some bad news for the Great Barrier Reef, with experts declaring another mass bleaching—the fifth in just eight years. We find out what coral bleaching is and how it's impacting Australia's World Heritage-listed wonder.

A British Gas video featuring Amanda Lamb with tops tips on preparing your home for the winter, including information on bleeding radiators, insulating pipes, and checking boiler pressure.

Sting talks about the protection of the rainforest and the Rainforest Project of the Prince of Wales.

The Prince of Wales has set up a rainforest project in order to protect the remaining rainforests on this earth. He talks about the seriousness of climate change and how it will affect our lives and the lives of our children and grandchildren. He appeals to us to support him and his project.

Prince Charles launches a campaign to save the rainforests in an online video broadcast, featuring Hollywood stars Robin Williams, Daniel Craig and Harrison Ford, as well as Princes Harry and William.

Everyone's heard of California, but this documentary showcases the state's natural beauty and wildlife. It has a fascinating range of geographical features and is home to many unique species of animals.

Kelp is a fascinating plant. What we see on the surface has little in common with what's actually there. Californian harbor seals are mammals but they do a lot of hunting underwater.

Every fall, the monarch butterflies migrate back to their breeding grounds in California. These fascinating and stunningly beautiful creatures weigh only a gram, yet travel extraordinary distances to complete their lifecycle. In the early spring, deep in the Yosemite valley, the sun warms the wet ground, forming clouds of misty fog.

Alive since ancient times, the giant sequoia trees stand colossal and majestic. Deep in the valley, a pair of coyote hunt in the winter snow, while in the Mojave Desert, Joshua trees and cactus plants have adapted to survive the searing heat.

Life can be hard in the Californian desert, but many plants and animals are adapted to survive the hot, dry conditions. Jackrabbits, owls, hummingbirds, and the green stick tree all thrive in this harsh climate as they wait for the rare blessing of rain.

The harbor seals gather in a sheltered cove to give birth. But even hidden from predators, there is no guarantee of survival, and we witness the tragic death of one newborn that gets trapped in its amniotic sac. Within a few hours, the pups that survive the birth are already into the waves, getting to know their new watery world.

Off the coast of California, an island of floating kelp provides refuge for fish in the open waters. The many small fish then attract larger species, including the ocean sunfish that seek relief from their parasites, and the predatory blue shark.