This means that an essential part of Earth Systems modelling involves exploring the interplay across different systems, and developing models that take all of the systems into account. This requires integrating data from a wide variety of systems — and from a variety of sources, such as field measurements and remote sensing technologies.

One of the most high-profile attempts to quantify whole-Earth processes is the concept of “planetary boundaries”. This aims to identify a set of Earth systems, each of which is essential to human survival and wellbeing. An initial assessment in 2009 identified nine, ranging from biosphere integrity and fresh-water use to land system change.¹⁴ It further concluded that humanity had already pushed past three of the boundaries, taking our species outside its “safe operating space”.¹⁵> However, there are large uncertainties around the size and rate of change we are causing, whether the current list of boundaries should be amended,¹⁶ and how the different boundaries interact. The “boundaries” framing has also been questioned: in the absence of tipping elements, Earth systems degrade gradually so hard limits are difficult or impossible to specify.