This episode explores the nature of the greenhouse effect (discovered by Joseph Fourier and Svante Arrhenius), and the evidence demonstrating the existence of global warming from humanity's influence. Tyson begins by describing the long-term history of the planet Venus; based on readings from the Venera series of probes to the planet, the planet had once had an ocean and an atmosphere, but due to the release of carbon dioxide from volcanic eruptions, the runaway greenhouse effect on Venus caused the surface temperatures to increase and boiled away the oceans. Tyson then notes the delicate nature of the amount of carbon dioxide in the atmosphere can influence Earth's climate due to the greenhouse effect, and that levels of carbon dioxide have been increasing since the start of the 20th century. Evidence has shown this to be from mankind's consumption of oil, coal, and gas instead of from volcanic eruptions due to the isotopic signature of the carbon dioxide. The increase in carbon dioxide has led to an increase in temperatures, in turn leading to positive feedback loops of the melting polar ice caps and dethawing of the permafrost to increase carbon dioxide levels. Tyson then notes that humans have discovered means of harvesting solar power, such as Augustin Mouchot's solar-driven motor in the 19th century, and Frank Shuman's solar-based steam generator in the 1910's. Tyson points out that in both cases, the economics and ease of using cheap coal and oil caused these inventions to be overlooked at the time. Today, solar and wind-power systems would be able to collect enough solar energy from the sun easily. Tyson then compares the motivation for switching to these cleaner forms of energy to the efforts of the Space race and emphasizes that it is not too late for humanity to correct its course.

'In Search of Beethoven': takes a comprehensive look at the composer's life through historical research and Beethoven's biography and letters, but with the emphasis always on the performance -- and interpretation -- of Beethoven's music. From his early piano concertos through the "Moonlight Sonata," "Für Elise," and the immortal notes of the Fifth and Ninth Symphonies, Beethoven's music remains as beloved, popular, and relevant as any work of art has ever been. "In Search of Beethoven" brings together the world's leading performers and experts on Beethoven to reveal new insights into this celebrated composer.

The film follows the dramatic journey of three whistleblowers who are determined to break the silence around one of the most controversial current affairs issues of our time: the secret U.S. drone war. At the center of the film are three U.S. military veterans. Plagued by guilt over participating in the killing of faceless people in foreign countries, they decide to speak out publicly, despite the possible consequences. Their stories take dramatic turns, leading one of the protagonists to Afghanistan where she learns about a horrendous incident. But her journey also gives hope for peace and redemption. National Bird gives rare insight into the U.S. drone program through the eyes of veterans and survivors, connecting their stories as never seen before in a documentary. Its images haunt the audience and bring a faraway issue close to home.

In the fall of 2016, an army of over 100,000 Iraqi soldiers and militiamen mobilize to liberate Mosul, Iraq's second largest city, from the clutches of the Islamic State. Ali Mula, an Iraqi journalist, joins this army of uneasy allies--including Sunnis, Shiites, Christians and Kurds--to find out if they can put aside their sectarian differences and finally free their country from the scourge of ISIS.
Along the way to Mosul, Ali encounters an unforgettable group of characters including a Sunni tribal leader who calls himself 'the Crocodile', a female militia leader avenging the death of her husband, a canny, Iranian-backed militia leader, a lawyer-turned-warrior, an elite band of ISIS killers, and refugees who survived the brutality of ISIS occupation. As he nears the end of his journey, Ali meets face-to-face with a die-hard ISIS prisoner who reveals the truth behind his nefarious organization.

Cannabis is the world's favourite drug, but also one of the least understood. Can cannabis cause schizophrenia? Is it addictive? Can it lead you on to harder drugs? Or is it simply a herb, an undervalued medicine? Addiction specialist Dr John Marsden discovers that modern science is finally beginning to find answers to these questions. John traces the cannabis plants' birthplace in Kazakhstan; finds the origins of our sensitivity to cannabis in the simple sea squirt; and finds out just what it does to our brains. He meets people who have been changed by this drug in drastically different ways - from those whose lives have been shattered to those who lives have been revived.

Professor Diarmaid MacCulloch - one of the world's leading historians - reveals the origins of Christianity and explores what it means to be a Christian. In the first episode, he overturns the familiar story that it all began when the apostle Paul took Christianity from Jerusalem to Rome. Instead, he shows that the true origins of Christianity lie further east, and that at one point it was poised to triumph in Asia, maybe even in China. The headquarters of Christianity might well have been Baghdad not Rome, and if that had happened then Western Christianity would have been very different.