**1. Introduction**

Human-induced climate change threatens ecosystems and populations around the world today and increasingly in the future [1]. The majority of countries around the world recognize that only collective action will mitigate climate change. This led to 197 countries coming together in 1992 to adopt a multilateral environmental treaty called the United Nations Framework Convention on Climate Change. Their objective was "stabilization of greenhouse gas concentrations in the atmosphere at a level that would prevent dangerous anthropogenic interference with the climate system. Such a level should be achieved within a time frame sufficient to allow ecosystems to adapt naturally to climate change, to ensure that food production is not threatened and to enable economic development to proceed in a sustainable manner" [2]. The timing of this agreemen<sup>t</sup> is relevant given that there was less scientific evidence at the time regarding climate change, and ye<sup>t</sup> member States were driven "to act in the interests of human safety even in the face of scientific uncertainty". It took more than 20 years to agree on the common goal of keeping climate change-related temperature increases to less than 2 degrees, and to pursue efforts to limit global heating to 1.5 degrees, through the 2015 Paris Agreement [3].

The first round of nationally determined contributions was largely complete (186 submissions from 197 members) by 2020. Studies have modeled the implementation measures

**Citation:** Salem, J.; Lenzen, M.; Hotta, Y. Are We Missing the Opportunity of Low-Carbon Lifestyles? International Climate Policy Commitments and Demand-Side Gaps. *Sustainability* **2021**, *13*, 12760. https://doi.org/ 10.3390/su132212760

Academic Editor: Grigorios L. Kyriakopoulos

Received: 29 September 2021 Accepted: 8 November 2021 Published: 18 November 2021

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and goals set out in the nationally determined contributions and the consensus is that they are not sufficient to reach the 2-degree binding, or 1.5-degree aspirational, goal [4]. UNEP's 2020 Emission Gap Report estimates that the global emissions resulting from nationally stated mitigation ambitions currently submitted under the Paris Agreement would lead to global greenhouse gas emissions in 2030 of 53–56 GtCO2-eq per year, aligned with 3 degrees of global heating. Modeled trajectories of global anthropogenic emissions limiting global heating to 1.5 degrees are in the 25 GtCO2-eq per year range [4].

The implications of this mismatch between goals and trajectories are significant. It means more widespread disruption to climate as well as changing ecosystem services that are fundamental to supporting a functional economy and global population of 10 billion [1].

In most cases, analysis indicates that each country's NDC indicates that it would use most of its allowed emissions space for the entire 21st century by 2030 [5], showing that there is a need to look beyond the conventional strategies for climate change mitigation, or that planned measures are not being included in the NDCs. There is consensus that technological solutions alone will not ensure that the 1.5-degree threshold is not crossed [6–9]. Furthermore, the time scales needed to implement these are long term due to the time needed to transition to low-carbon energy and infrastructure, thus they will not generate the immediate reductions needed, and even when they are in place, studies have shown that carbon reductions from technological improvements are far outweighed by carbon increases from economic growth [10].

The Paris Agreement states that "*sustainable lifestyles and sustainable patterns of consumption and production, with developed country parties taking the lead, play an important role in addressing climate change".* Recent studies estimate that two-thirds of GHG emissions are linked to household consumption—around 6 tCO2-eq per capita globally, and double that in North America [11]. Since household consumption is driving the majority of emissions, sustainable lifestyles and consumption patterns are a large opportunity for reductions.

This paper will explore whether sustainable lifestyles and sustainable consumption are reflected in nationally determined contributions to climate change mitigation and make the case for shifting the focus in the next round of NDCs from supply-side and territorial emissions to demand-side strategies encompassing low-carbon lifestyles.

We will first make and support our argumen<sup>t</sup> that demand-side strategies involving drastic lifestyle changes are required to meet the 1.5-degree goal. We will then review whether, where, and to what extent NDCs embrace measures that consider and support lifestyle changes and explore what barriers might exist that prevent governments from implementing such measures. Finally, we will conclude with recommendations and a future outlook for policy.
