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[Climate Change] The problem with plans to limit warming to 1.5°C

A few years ago the United Nations IPCC wrote a special report on limiting global warming to below 1.5°C (SR15). At the time, I wrote a policy brief criticising the way IPCC produced the report. In summary, to get below 1.5°C, we have to deal with technologies and social changes that do not exist today, and that is not designed to take into account the SDGs other than climate change. Here is an extract from the policy brief I wrote at the time.

Van Vliet, O., & Takama, T. (2018). (Rep.). Climate Strategies. Retrieved July 14, 2021, from

2. Integrated assessment models in SR15

SR15 suggests that global warming can still be kept below 1.5°C, and that this would make the UN Sustainable Development Goals (SDGs) much more achievable.

However, this is an unprecedented task and will require an intense effort of rapid decarbonisation across many sectors. Various pathways are possible for achieving this, but the overall message to all stakeholders is that global greenhouse gas (GHG) emissions must be cut by half before 2030 compared to 2010, with the long term aim of net zero carbon dioxide (CO2) emissions by 2050. SR15 also states that Carbon Dioxide Removal (CDR) technologies that lead to ‘negative’ emissions will need to be deployed in the second half of the century, especially if global temperatures temporarily overshoot the 1.5°C limit. However, the report does not describe a business model through which these ‘negative’ emissions might be funded.

The various pathways in SR15 are variants of model scenarios, with coherent ‘assumptions regarding future trends in population, consumption of goods and services (including food), economic growth, behaviour, technology, policies and institutions’ (chapter 2, section 2.1.1). They are used in SR15 to explore many different technological and behavioural changes needed to limit climate change, often at an aggregated scale, and reflect on the economic and environmental impacts of those changes. These changes include electrification of transport and heating, efficiency increases in industrial process and appliances, reduced food loss and waste, and promotion of sustainable behaviours and lifestyles (e.g. increased use of non-motorised and public transport).

However, the scenarios in SR15 do not represent how decisions on climate change policy are actually arrived at. In reality, low-carbon transition policies are more likely to be made for reasons tangentially related to climate change, such as job creation or improving public health. They are also highly dependent on the local context.

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