Every day, unimaginable amounts of energy hit the Earth in the form of sunlight. Much of this energy is radiated back into space, but greenhouse gases reduce the Earth’s ability to shed heat and instead keep it trapped inside the atmosphere. To get a sense of how much heat we are talking about, we can express it in terms of Hiroshima-sized nuclear bombs. Compared to pre-industrial times, how much more heat would you guess the Earth is retaining? The equivalent of one nuclear bomb per year? Per month? Per week? Per day? The reality is that the extra heat being trapped amounts to four nuclear bombs per second, of every minute, of every hour, of every day, three hundred and sixty-five days a year.