It\u2019s a bit worrying when a scientific paper begins, \u201cHow long will life on Earth survive?\u201d But in this case\u2014a study by Jacob Haqq\u2010Misra of Blue Marble Space and Eric Wolf at the University of Colorado Boulder\u2014the billion-plus-year timeline under consideration shouldn\u2019t cause you too much existential panic.<\/p>\n
The context for this question is that we understand the Sun will brighten as it eventually matures into a red giant that swallows the Earth in a solar furnace. So, where along that 5 billion-year path will life on Earth, in fact, be cooked?<\/p>\n
Weathering and the weather<\/p>\n
This isn\u2019t just a question of incoming radiation. Among the thermostat-like stabilizing feedback loops in Earth\u2019s climate, the cycling of CO2 through the solid Earth is a major factor over timescales this long. The weathering of silicate rocks at the surface converts atmospheric CO2 into carbonate that ends up on the seafloor, where it can be subducted into the mantle with tectonic plates. (And eventually, it can cycle back out to the atmosphere through volcanoes.)<\/p>\n
The weathering of bedrock depends, in part, on temperature. Warmer temperatures and a more active hydrologic cycle mean an increased rate of weathering, which pulls more CO2 out of the atmosphere. That slows rising temperatures. But in this scenario, it could also lead CO2 to fall to extremely low levels\u2014and photosynthesis requires CO2.<\/p>\n