The ambition and target date for achieving Net Zero have relevant implications for justice towards: future generations, those vulnerable to climate impacts and those exposed to the required economic changes.
Achieving Net Zero by mid-century would allow us to limit warming to below 1.5°C and avoid the worst effects of climate change. Any earlier dates will increase our chances to succeed and could reflect different historic contributions to emissions, where those most responsible for polluting should aim to reach Net Zero first.
Beyond a target date, in the spirit of high ambition, we need to act now and set short-term milestones. Credible ambitious Net Zero pledges have concrete plans and are backed by resources which drive rapid decarbonization and GGR scaling.
What is our temperature ambition and where are we at now?
The aim of the Paris Agreement is to limit global average warming to no more than 2°C above pre-industrial levels, whilst pursuing efforts to limit warming to 1.5°C.
So far, the Earth has experienced 1.1oC of warming at 0.2-0.25oC per decade. Therefore, given current practices we will reach 1.5oC in 15-20 years.
When do we need to achieve Net Zero to keep within "safe" temperature limits?
The sooner that action is taken to achieve net zero for greenhouse gas emissions, the greater the likelihood that global warming can be kept well below 2°C. This calls for countries to have the highest possible ambition in their emissions reduction strategies.
The Intergovernmental Panel on Climate Change (IPCC) has modelled various emissions pathways for different warming levels. Many of these scenarios suggest that global net zero emissions need to be achieved by around 2050 if warming is to be limited to 1.5°C.
However, the exact date is uncertain given inconsistent emission accounting methods. Emissions back-calculated from atmospheric data (using models) are higher than the values reported in national inventories. There are also uncertainties regarding the possibility of increasing "natural" emissions in the future, for example, arising from an increasing frequency of forest fires. In light of this uncertainty, we cannot preclude the possibility of long-term CO2 removal to keep temperatures stable. Net zero may not be achieved at a specific date, but rather be an ongoing inter-generational goal.
The difference between 1.5°C and 2°C warming may seem small. But the likely climate impacts at the two temperature increases are vastly different. They are global averages and don't reflect regional differences in warming (which are higher over land and in polar regions) or the many interconnected effects. Even small changes in ocean temperatures can be fatal for sensitive species such as corals. Ocean warming also increases ocean volume, causing sea level rise, and increases the frequency and strength of storm events, in temperate as well as tropical regions. Each effect has the potential to trigger further changes, and as temperatures rise so do the complexity and severity of the impacts.
The societal risks and impacts of warming greater than 1.5°C are particularly high for developing nations who have been least responsible for greenhouse gas emissions and who are least capable of adapting to climate change. For many people who live in developing small island states and low-lying coastal areas, a global temperature rise of 2°C will be life-threatening and economically catastrophic. Such conditions could result in massive shifts of population and migrant flows.
If we have until 2050, why do we need to act urgently?
A national target for Net Zero by 2050 may sound far in the future, but action to achieve it is needed now. Delayed action increases damaging climate impacts (including floods, droughts and fires, and sea level rise) inducing taxing socioeconomic conditions (such as economic crisis, new diseases, and climate migration) everywhere on the planet. Further, the longer we take to reduce greenhouse gas emissions, the harder it will become to remove them. This burdens future generations with high levels of risk and responsibility under increasingly difficult circumstances.
The decisions we make now will affect future actions and needs. If we have empathy for future generations, it is only fair we protect them by removing the greenhouse gases current generations have emitted.
What should a just transition look like?
The notion of a ‘just transition’ appeals to ensuring that efforts toward decarbonisation are underpinned by equity and social justice goals. When designing strategies to achieve Net Zero it is important to pay attention to the protection of jobs and livelihoods, democracy, decentralisation, energy ownership, economic restructuring, and redistribution of wealth. We need to act urgently, but must avoid leaving people behind.
Further, given different levels of economic activity, developing countries often generate much lower levels of greenhouse gas emissions compared to developed nations- particularly when accounting for historic emissions. This raises issues of fairness in determining contributions to Net Zero. The UN therefore places special responsibility for mitigation on the shoulders of developed countries. Those who have benefited most from past carbon emissions should reduce their emissions as soon as possible to allow developing countries greater use of the remaining carbon budget.