The Atmosphere report considers both the resilience of the climate system itself and the resilience of our society to climate change.
Our planet is somewhat resilient to increasing CO2 levels because atmospheric CO2 is absorbed by the oceans. During recent decades, the oceans have taken up approximately 25 per cent of the annual anthropogenic CO2 emissions to the atmosphere. However, the capacity of the oceans to absorb CO2 appears to be limited, because the absorbed CO2 is making our oceans more acidic, with consequent environmental impacts.
Significant lag also exists in the system. Modelled projections show that, if CO2 levels are returned to pre-industrial concentrations, it would take more than 900 years for surface air temperature and sea level to return to pre-industrial levels.
Resilience of a society to climate change is dependent on the sensitivity of the society to change and its capacity to adapt to change. The Intergovernmental Panel on Climate Change (Field et al. 2014) considers adaptation as a means to build resilience within society and adjust to climate change impacts. Climate-resilient pathways may involve significant transformations in political, economic and socio-technical systems. The success of climate-resilient pathways is linked to the success of climate change mitigation (i.e. as problems become unmanageable, future options for climate-resilient pathways may be reduced).
In 2015, the Australian Government released a National Climate Resilience and Adaptation Strategy (Australian Government 2015d), which outlines how Australia is building resilience against future climate risks. It identifies principles to guide effective adaptation practices and management.
Because air quality in Australian cities is usually restored to acceptable levels once localised emissions from point sources change, urban airsheds are considered to be highly resilient.
Humans are less resilient to major pollutants at current levels in Australian cities. Air pollution causes premature mortality and increased hospital admissions because of respiratory and cardiovascular symptoms. For major pollutants (including particles and ozone), studies suggest that there is no safe level at which health effects do not occur; impacts occur at lower particulate levels than standards were designed to achieve.