2. Climate Science

The Intergovernmental Panel on Climate Change (IPCC) is the main international scientific body on climate change and issues periodic assessment reports.^[1] The most recent IPCC Assessment Report concludes that it is ‘unequivocal’ that GHG-emitting human activities are the primary cause of global warming since the mid-20th century.^[2] The primary emissions-intensive activities driving global warming are first, fossil-fuel combustion and industrial activities, and second, the clearing of land for agriculture, industry and other human activities.^[3] These activities contribute to the emission of four main GHGs (carbon dioxide, nitrous oxide, methane and halocarbons). GHG emissions trap heat in the atmosphere, leading to global warming and the consequential impacts of climate change. Concentrations of carbon dioxide in the atmosphere are unprecedented in comparison with the past 2 million years, and atmospheric concentrations of methane and nitrous oxide are higher than any time in the past 800,000 years.^[4] In this context, global temperatures have already risen by approximately 1.2°C since the pre-industrial era.^[5] Moreover, states’ GHG emission reduction commitments set the world on a course for a global temperature rise of an estimated 2.9°C by 2100.^[6]

Human-induced climate change is associated with the increased occurrence and severity of extreme events, such as heatwaves and floods, as well as slow-onset events like temperature rise and ocean warming. These extreme and slow-onset events are already causing widespread but unevenly distributed adverse impacts and related losses and damages to natural and human systems, such as losses of biodiversity and ecosystem services; food and water insecurity; harmful outcomes for human health; damage to cities, infrastructure and settlements; and losses of territory, cultural heritage and Indigenous or local knowledges. Those that have contributed least to historic and current GHG emissions often face the first and worst impacts of climate change.^[7] Conversely, those that have contributed most to the causes of climate change, and thus benefited most from GHG-intensive activities, now possess more resources to respond and adapt to the impacts of climate change.

Australia is in a unique position with respect to climate change, being highly vulnerable to the impacts of climate change while also disproportionally contributing to atmospheric GHG emissions relative to its population size. In Australia, temperatures have risen by an estimated 1.47°C since 1910.^[8] This temperature rise has contributed to in an increased risk of bushfires in Australia.^[9] Simultaneously, surrounding sea levels are rising at a rate faster than the global average, resulting in coastal erosion and flooding throughout Australia’s coastal regions and low-lying islands.^[10] The degradation of Australia’s coral reefs and marine biodiversity similarly illustrates the adverse impacts of climate change in our region. Australia’s coral reefs provide critical habitats for marine biodiversity and support ecosystem services in the coastal environment, such as fisheries productivity, drawing carbon from the atmosphere (‘carbon sequestration’) and helping to reduce marine pollution.^[11] The degradation of Australia’s marine environment therefore has implications for economic and food security^[12] and the capacity for Australia to achieve and uphold emission limitation and reduction standards,^[13] as well as the continued habitability of surrounding low-lying islands.^[14]