How can we address the causes of climate change?

The world is warming due to increasing concentrations of greenhouse gases in the atmosphere.

In Australia, the consequences of a warming world are evident. Climate change is impacting environment, economy and Australian people. Australia has experienced:

• Its hottest and driest year in 2019 with a record-breaking number of days over 39 °C
• Three widespread marine heatwaves during 2016–2020
• Three major floods in eastern Australia during 2019–2021
• Major fires in southern and eastern Australia during 2019–2020
• Fewer cold days in the region.

In the future, we can expect further warming and sea-level rise, with more hot days and heatwaves, less snow, more rainfall in the north, less April–October rainfall in the southwest and southeast and more extreme fire weather days in the south and east.

Overall, the future climate-related impacts we experience in Australia will depend on the level of global warming that is reached.

Paris Agreement: An international treaty on climate change

Australia is among 197 countries that have signed on to the United Nations Framework Convention on Climate Change’s Paris Agreement which was developed to strengthen the global response to the threat of climate change.

The Agreement has 3 main aims:

1. Holding the increase in the global average temperature to well below 2 °C above pre-industrial levels and pursuing efforts to limit the temperature increase to 1.5 °C above pre-industrial levels.
2. Increasing the ability to adapt to the adverse impacts of climate change and foster climate resilience and low greenhouse gas development, in a manner that does not threaten food production.
3. Making finance flows consistent with a pathway towards low greenhouse gas emissions and climate-resilient development.

The chance of limiting global warming and achieving the goals of the Paris Agreement is dependent on how quickly global greenhouse gas emissions can be reduced. This is reliant on emissions-reduction policies of governments, and how effectively they are implemented and enabled by technology, businesses and communities.

The globally-averaged temperature in 2023 was 1.52 °C above pre-industrial levels.

Based on current global policy settings, greenhouse gas emissions will continue to rise, leading to higher atmospheric concentrations of CO₂ and a global warming of 2.7 °C by 2100.

Mitigation through emissions reductions

The main goal of climate mitigation is to reduce greenhouse gas emissions from human activities. Globally, we need to reduce greenhouse gas emissions as fast as we can if we are to limit rising global temperatures.

Technologies to reduce emissions include new and renewable forms of energy that do not use fossil fuel, such as wind, solar and biofuels.

Energy efficiency can reduce demand for fossil-fuel generated energy to also reduce emissions of carbon dioxide.

In order to keep globally averaged temperatures from rising beyond 1.5 °C in the long term, global carbon emissions will need to reach net zero by around 2050.

Each sector will face different emissions reductions challenges and opportunities on the path to net zero.

Energy sector

Reducing emissions across the energy sector requires major transitions, including a substantial reduction in overall fossil fuel use, renewable energy sources, switching to biofuels and hydrogen, improved energy efficiency and demand management.

Agriculture

Sustainably sourced agricultural and forest products can be used instead of emissions-intensive products. Agricultural intensification (i.e. change in crop and noncrop vegetation and management practices on farms) can reduce methane and nitrous oxide emissions and ecosystem impacts.

Industry

Reducing industry emissions will entail coordinated action throughout value chains, including demand management, energy and materials efficiency, circular material flows, and major changes in production processes.

Buildings

Retrofitting existing buildings and innovations for new buildings include energy-smart building designs, low-emission construction materials and efficient appliances.

Transport

Changes in urban form, consumer behaviour and public transport can reduce demand for transport services and shift to more energy efficient transport modes. Electric vehicles, sustainable biofuels and low-emissions hydrogen can support emissions reductions from shipping, aviation and heavy-duty land transport. Many strategies have co-benefits, including air quality improvements, health benefits and reduced congestion.

Mitigation through avoided emissions

Where we cannot reduce fossil fuel use by switching to renewable energy sources, carbon dioxide can still be removed at the point of source of large emissions (such as power stations) and stored underground. This is otherwise known as carbon capture, utilisation and storage (CCUS) technology.

CCUS technology is used to limit the amount of greenhouse gases that would otherwise have been emitted at the point of source of emissions. It cannot actively draw down atmospheric carbon dioxide levels (i.e. carbon dioxide that has previously been emitted in the atmosphere).

Mitigation through enhancement of natural sinks

Nature-based carbon ‘sinks’ on land and the ocean absorb about 50 per cent of global carbon emissions. Efforts to restore and protect natural carbon stores in the land and ocean e.g. by planting trees, limiting land clearing, or rejuvenating blue carbon systems are important and in many cases provide co-benefits for the environment e.g. biodiversity.

Enhancing natural sinks cannot, however, completely or reliably offset the carbon dioxide emissions currently generated by humans. This is primarily because the natural carbon cycle removes carbon dioxide over decades to centuries. This means the rate of removal in natural carbon sinks is too slow.

There are also some limitations in terms of what can be stored, and for how long (durability). Land sinks, for example, are less effective in storing carbon when land is cleared or degraded. Land sinks are also susceptible to extreme events like heat waves and fires, resulting in the release of carbon dioxide back to the atmosphere. Ocean carbon sinks can also release dissolved carbon dioxide back to the atmosphere when the atmosphere is warmer.

Mitigation through carbon dioxide removal

Limiting warming to 1.5 °C will need to involve major use of novel carbon dioxide removal technologies, which are designed to permanently remove carbon dioxide from the atmosphere.

Without novel carbon dioxide removal approaches, historic and ongoing contributions of carbon dioxide will remain in our atmosphere for centuries to come. This imbalance means that our global atmospheric temperature will continue to increase.

Some novel carbon dioxide removal solutions are available to us now, such as direct air capture, or biochar, but require concerted testing and development if they are to be deployed at scale.