The climate is changing more quickly now than it has done for tens of millions of years. This was the blunt conclusion to the BBC’s recent Earth series, which sought to convey to viewers how cataclysmic the disruption caused by global heating could be. Chris Packham, its presenter, described the tipping points that were reached 56m years ago, when, over the course of a few thousand years, temperatures climbed by 5C. Fossil records from this period are one resource that modern scientists use when trying to predict the consequences of the much faster heating that is now under way.
Planetary boundaries, about which scientists this week issued an updated warning, are another tool for thinking about the environment. These are a set of parameters defined at the Stockholm Resilience Centre, led by Prof Johan Rockström, in 2009. They are limits within which changes to the Earth’s life support systems, which have been relatively stable for 10,000 years, can be considered manageable. Once the boundaries are breached, however, everything becomes much more extreme, unstable and threatening. As well as an attempt at quantifying the disruption that natural systems can withstand, the nine boundaries represented an attempt to broaden understanding of the risks. One key message was that global heating caused by greenhouse gases trapped in the atmosphere is not the only threat.
