Sagan discusses comets and asteroids as planetary impactors, giving recent examples of the Tunguska event and a lunar impact described by Canterbury monks in 1178. It moves to a description of the environment of Venus, from the previous fantastic theories of people such as Immanuel Velikovsky to the information gained by the Venera landers and its implications for Earth's greenhouse effect. The Cosmos Update highlights the connection to global warming.

The extraordinary wildlife, culture and history of this immense, fascinating ocean and its myriad islands are revealed in stunning detail. With its coral reefs, turquoise lagoons and dramatic oceanic atolls, the South Pacific is the archetypal paradise. It is still relatively healthy and teeming with fish, but it is a fragile paradise. International fishing fleets are taking a serious toll on the sharks, albatross and tuna, and there are other insidious threats to these bountiful seas. We look at what is being done to preserve the ocean and its wildlife.

Today, the topic of climate change is a major part of daily life, yet 40 years ago it was virtually unheard of. Since then, Horizon have followed scientists as they have tried to unpick how the climate works and whether it is changing. Dr Helen Czerski delves into this unique archive to chart the transformation of a little-known theory into one of the greatest scientific undertakings in history. It has been a constantly surprising journey of discovery that has revolutionised our understanding of climate, and seen scientists face unprecedented controversy and criticism.

In a far cry from the steamy jungles of Rwanda or the icy waters of the Arctic, British naturalist Sir David Attenborough has donned a necktie and met with US president Barack Obama to discuss climate change and the future of the planet. The two met at the White House — a place the naturalist had never yet explored — on Sir David's 89th birthday in May to film the interview". It was the first time the respected wildlife filmmaker had met an American president and he seemed a little awed by the experience. Mr Obama, who grew up watching Sir David's programs, seemed equally thrilled. The president has the environment and climate change on his radar and is anxious to see progress made as his presidency comes to a close. He faces stiff opposition from Republicans in Congress on his plans to tackle climate change, but remains determined to make changes before leaving office. "I don't have much patience for anyone who denies that this challenge is real," he said. "We don't have time for a meeting of the Flat Earth Society." Sir David, who has been called "the godfather of natural history TV" by the BBC, brought to the meeting six decades dedicated to sharing the wonders of the natural world with television audiences. After initially being rejected for television because his teeth were deemed "too big", Sir David went on to make his Life on Earth television series, which has been watched by more than 500 million people worldwide. His name is now synonymous with nature, conservation and wildlife. During the television interview, the men discussed global warming, renewable energy and how children and young people hold the key to reversing the damage.

Follow the shocking, yet humorous, journey of an aspiring environmentalist, as he daringly seeks to find the real solution to the most pressing environmental issues and true path to sustainability. Discover 'The Facts' http://www.cowspiracy.com/facts

Hosted by ABC journalist Bob Woodruff, this two-hour special explores what a worst-case future might look like if humans do not take action on current or impending problems that could threaten civilization. The problems addressed in the program include climate change, overpopulation, and misuse of energy resources. The events parallel the life of a fictitious storyteller, 'Lucy' as she describes how the events affect her life. The program included predictions of a dystopian Earth in the years 2030, 2050, 2085, and 2100 by scientists, historians, social anthropologists, and economists, including Jared Diamond, Thomas Homer-Dixon, Peter Gleick, James Howard Kunstler, Heidi Cullen, and Joseph Tainter. According to Executive Producer Michael Bicks, "this program was developed to show the worst-case scenario for human civilization. Again, we are not saying that these events will happen — rather, that if we fail to seriously address the complex problems of climate change, resource depletion and overpopulation, they are much more likely to happen.