evidence: This provides much-needed context to the current phase of warming. In fact, scientists estimate the Earth hasn't been this hot for about 125,000 years. [...] The number of weather-related disasters has increased by a factor of five over 50 years [...] There is abundant evidence for mass extinctions of life during these periods. And climate models suggest that, at times, the tropics could have become "dead zones", external, too hot for most species to survive.