The challenge of climate change has been defined as a ‘super-wicked’ problem. It needs urgent responses. It needs those responsible to accept responsibility, and provide solutions and support. It requires aspects of sovereignty to be ceded to an international body, or that wide-ranging powers be conferred to a central body at the national level. And it carries perverse incentives to push action into the future.

Despite these complexities, international negotiations to address the challenge of climate change have been underway since the UN Conference on Environment and Development at Rio in 1992, and under the aegis of the UN Framework Convention on Climate Change (UNFCCC) since 1994.  The first protocol on climate change – the Kyoto Protocol – was adopted at the third Conference of the Parties (COP) to the UNFCCC in 1997. Since then, negotiations have continuously evolved to culminate in the Paris Agreement at the 21st COP in December 2015.

The task of comprehensively assessing the relevant science was given to the Inter-governmental Panel on Climate Change (IPCC). IPCC’s first assessment report was published in 1990, and it has since been regularly assessing the growing body of literature on impacts, vulnerability and mitigation options for climate change. Governments have a key role in nominating authors and approving texts. These assessments have had a key influence on the global negotiation processes.

Scientific assessments undertaken by IPCC have emphasised the need to limit global average temperature increase to below 2°C, but also covered a range of likely scenarios up to a 6°C increase and beyond. Political negotiations, however, have consistently disregarded the high-end scenarios that could lead to abrupt, irreversible or runaway climate change. This was despite scientific evidence that risks associated with tipping points “increase disproportionately as temperature increases between 1–2°C additional warming and become high above 3°C”.

Thus, in the lead up to and during the Paris negotiations, the need-based focus was on ensuring that temperature increases “remained well below 2°C”. However, pessimism relating to the actual ability to conform to the 2°C trajectory could have led to modest pledges and delays in mitigation efforts, implying exponentially higher costs of subsequent adaptation actions. Paradoxically, on the assumption that the world would limit temperature increases to 2°C, the Paris Agreement is nowhere close to the ambition required on adaptation and resilience building. As such, despite the fact that the current pathways offer a very high probability of exceeding the 2°C guardrail, the world is currently completely unprepared to envisage, and even less deal with, the consequences of catastrophic climate change.

The Sendai Framework for Disaster Risk Reduction (2015-2030), which was the outcome of inter-governmental negotiations supported by the UN Office for Disaster Risk Reduction at the behest of the UN General Assembly, adopted in March 2015, could have addressed itself specifically to the risks emanating not just from the aspirational 2°C scenario but the almost equally likely scenario of tending towards a 3°C to 4°C world.  Instead, it generically limited itself to be “within the mandate of the United Nations Framework Convention on Climate Change under the competences of the Parties to the Convention”.

The Paris Agreement came into force in October 2016, with national pledges falling woefully short – setting the world on a 3.4°C  temperature increase track. Although climate change action has now become part of mainstream economic and social strategies in most countries, the United States has since withdrawn from the Climate Agreement. Not only does this greatly increase the burden of responsibility on other countries but also substantially reduces the funding for climate initiatives, thereby further increasing the risk of catastrophic climate change. In this context, the world needs to pay a lot more attention to adaptation measures than was already called for!

Climate change scenarios

One central method to assess the expected increase of average global temperatures is the development of climate change scenarios. Those scenarios are descriptions of alternative futures, where total greenhouse gas emissions and the resulting global temperature increase are projected on the basis of various socio-economic factors affecting emission levels, including population growth, economic activity, technological change, as well as governance and cultural values. These scenarios typically compare the anticipated effects of various parameters – particularly the anticipated effects of various changes in policy settings – with a ‘business-as-usual’ situation, and play an important part in both policy development and climate change negotiations, on a national and global level.

A global carbon law roadmap to make Paris goals a reality

The Paris Agreement on climate commits countries to take action to keep global average temperature “well below 2°C above pre-industrial levels and to pursue efforts to limit the temperature increase even further to 1.5°C”. To aim for the 1.5°C target, the total carbon dioxide that can be emitted in humanity’s remaining time on Earth – known as the carbon budget – is small. For a mere 50% chance of hitting this target, the carbon budget left from 2020 onwards is just 400 billion tonnes (Gt) of carbon dioxide. If we were to consider a higher target, for a 66% chance of keeping global temperatures below 2°C, from 2020 onwards, the world has a remaining carbon budget of 680 Gt of carbon dioxide that it can emit – although more recent updates suggest the budget for that target could be higher, so that reaching this target could be within our grasp with immediate action on an unprecedented scale. The world currently emits over 400 Gt of carbon dioxide every decade, so it is likely the world will overshoot the 1.5°C target. Therefore, in addition to reducing emissions to around zero, the world will need to draw carbon dioxide out of the atmosphere at scale in order to meet the Paris Agreement. This requires immediate, massive, globally-coordinated action. In 2017, an international team of researchers developed and published a roadmap for rapid decarbonisation that reduces the risk of Earth passing the 2°C threshold. The analysis can be summarised as a “Carbon Law”, a rule of thumb analogous to Moore’s Law in the IT sector, of halving emissions every decade to approach zero by 2050 or 2060, turn carbon sources to sinks and develop new carbon sinks. This is explained in the graph below. The next stage in the roadmap development will be launched at the Global Climate Action Summit in San Francisco in September 2018.