New Scientist: THE 20th round of climate talks in Peru's capital city Lima this month are seen as a crucial step towards reaching a global agreement in Paris in 2015. One of the things that is likely to be discussed is whether the 2 °C target the threshold between "acceptable" and "dangerous" climate change should remain the world's linchpin climate policy goal. In recent months, the validity and appropriateness of this ubiquitous target have been called into question. Concerns about the 2 °C target centre...