Climate scientists consider climate change to be among top threats to humanity's future. If unchecked, runaway climate change can destroy not just many of our current ecosystems, but wreak havoc in human societies as well. To prevent the worst catastrophe, greenhouse gas emissions from our energy system needs to decline to zero rapidly. We need to replace fossil fuels, which represent roughly 85 % of our energy production, with low-carbon alternatives. To manage this in a low-risk and timely manner, all tools need to be utilized to their maximum potential, including nuclear energy. Nuclear is surrounded by colourful rhetoric, politics, fear and fearmongering, click-bait scandal-headlines and mental images of dangerous radiation and catastrophic accidents. But how much of this is warranted, and how much is based on beliefs, opinions and prejudices? How dangerous is ionizing radiation really? What happened in Chernobyl and Fukushima, and what are the best estimates on their effects on public health and the environment? And can we harness nuclear energy to play a major role in decarbonizing our energy systems rapidly and more affordably?This book takes a serious look how the climate change mitigation is progressing, what needs to be done, and how nuclear has helped in the past, and can help us in the future. Partanen is an award-winning science writer and analyst on climate, environment, energy and society. Korhonen did his PhD in the history of technology, has written about climate and energy for years and is currently researching "Plan B", and emergency program for climate change mitigation.