“Human activities, principally through emissions of greenhouse gases, have unequivocally caused global warming”
– The opening line of the IPCC’s Sixth Assessment Report, published in 2023 [1]
Climate change is the greatest and most urgent challenge facing humanity. Our consumption of fossil fuels has emitted enormous quantities of greenhouse gases into the atmosphere, enhancing the greenhouse effect which traps solar radiation therein [2]. This trapped radiation has warmed the Earth significantly: between 2011 and 2020, Earth’s global average surface temperature was approximately 1.1OC higher than it had been during the latter half of the 19th Century [1]. Warming on this scale has devastating consequences, which shall only worsen as temperatures continue to rise [2]. These consequences are felt across the globe, although developing nations are impacted most harshly [2]. Such impacts are vast and varied – spanning the environmental, ecological, social and economic [1]. Climate change is a grave and long-term issue – and, as such, shall require a global and systematic solution [2].
The journey towards a global solution for climate change has been a long and winding one, strewn with obstacles and replete with wrong-turns and dead-ends. Our progress on that journey has also been reliant upon science for a map. A keystone in climate science is the work of the Swedish physical chemist Svante Arrhenius who, in 1896, was the first person to quantify the influence of carbon dioxide (CO2) upon Earth’s temperature [3,4]. Arrhenius demonstrated that changes to the concentration of CO2 in the atmosphere regulate the proportion of solar radiation that the atmosphere retains; at greater CO2 concentrations, the atmosphere retains a greater proportion of solar radiation, raising the average temperature of the planet [3]. This process was later termed the ‘greenhouse effect’, but it would not be associated with long-term global warming until several decades after its discovery [4].
The first person to detect this association was a British engineer named Guy Stewart Callendar [5]. In 1938, using data from 147 recording stations spread across the world, Callendar detected a 0.3°C rise in global land temperature between 1880 and the mid-1930s [6]. Through the use of a simple mathematical climate model, Callendar was able to attribute this warming to the burning of fossil fuels, which had increased the atmospheric CO2 concentration and thereby intensified the greenhouse effect [4,6]. Callendar predicted that further burning of fossil fuels would contribute to continued warming over the course of the 20th Century [6], but could not foresee the adverse impacts that this would have [4]. It would fall instead to Roger Revelle, an American oceanographer, to realise the threat posed by fossil fuel consumption, which he described as “a large scale geophysical experiment” [4,7]. Revelle led the earliest effort to raise awareness of temperature increase amongst policymakers and the media; whilst he met with little initial success, it was in a 1957 newspaper report on his work that the term ‘global warming’ was coined [8]. Research on this emerging problem continued nonetheless, with a range of important developments enabling more accurate assessment of the threat posed by climate change and more accurate predictions of its future implications.
One such development came from Charles David Keeling, an American geoscientist and student of Revelle’s, who commenced continuous atmospheric monitoring operations at Mauna Loa Observatory in Hawai’i [4]. Data from Mauna Loa demonstrated the continuous rise of the atmospheric CO2 concentration and helped bring the issue to a wider audience [8,9]. Also of pivotal importance was the Japanese climatologist Syukuro Manabe’s pioneering work on climate modelling [10,11,12], for which he was later awarded the Nobel Prize in Physics [13]. Climate models, such as those developed by Manabe, simulate the influence of a broad range of factors – from the greenhouse effect and ocean circulation to ecosystems and human societies – upon Earth’s climate [4]. These models have developed significantly over time and serve as the foundation of modern climate science [4,8].
At the same time, public concern on the issue of climate change was beginning to grow [8,14]. Spurred on by this concern and with climate model predictions as a scientific basis, the Intergovernmental Panel on Climate Change (IPCC) was established in 1988 [8,14] – fifty years after Callendar had first identified the trend of global warming. The purpose of the IPCC is to analyse the evidence for anthropogenic climate change, to assess its potential impacts and to devise that which is urgently needed: a solution [8,14,15]. In 1990, the IPCC published its First Assessment Report (FAR) [15]. Although this report was met with little public fanfare [8], it contributed to a turning point in the history of climate action. The UN Conference on the Environment and Development (UNCED) was set to be held in Brazil in June 1992 [14,16]. Known to posterity as the Rio Earth Summit, this conference had been tasked with establishing an international climate treaty [17] – a treaty for which the FAR would provide the scientific foundation [14]. The climate treaty which emerged from the Rio Earth Summit was the United Nations Framework Convention on Climate Change (UNFCCC) [18].
It is the UNFCCC which serves as the principal global negotiating framework for action on climate change [14,18]. To this day, the work of the convention is closely related to that of the IPCC [14], which has published five further assessment reports [1] – alongside a variety of special reports [2] – in order to inform climate policy [14]. Article 2 of the treaty that was signed at the Rio Earth Summit set out the objective of the UNFCCC: “to achieve… stabilisation of greenhouse gas concentrations in the atmosphere at a level that would prevent dangerous anthropogenic interference with the climate system” [18]. Work towards this objective requires consistent international cooperation, so Article 7.2 of the convention established a regular meeting for its 198 parties; this meeting, held annually from 1995 onwards, is referred to as the Conference of Parties – otherwise known as COP [18,19]. COPs serve as opportunities for countries to negotiate on the pace and direction of climate action and to monitor progress towards the UNFCCC’s goals [18,19]. A COP may produce a decision text, which can extend the ambition of the original convention [19]. For a decision to be effective, it is important that all parties agree to every word of the text, since this makes ratification and compliance more likely; parties do not have to ratify a decision text with which they disagree [19]. A wide variety of negotiating topics may be discussed at COP and included within a decision text.
Amongst the most prominent of these have been climate mitigation, which entails the prevention of further climate change by reducing greenhouse gas emissions; climate adaptation, which entails adjustment to the long-term impacts of climate change; and climate finance, which entails the provision of financial resources for mitigation and adaptation work, both from public and private sources [18,20]. One of the central principles of the UNFCCC is that these topics should be approached in a manner which reflects countries’ differing national circumstances and their differing historical contributions to climate change [21]. This is referred to as the principle of Common But Differentiated Responsibilities (CBDR) – or, alternatively, Common But Differentiated Responsibilities and Respective Capabilities (CBDR-RC) [18,21]. The principle holds that wealthier developed countries with greater cumulative historical emissions – known as ‘Annex I parties’ under the convention – should take the lead on climate action and should provide support to developing countries – known as ‘non-Annex I parties’ – which are both less responsible for climate change and more vulnerable to its impacts [18,21].
Several UNFCCC COPs have produced major decision texts. One of the earliest significant texts was the Kyoto Protocol, which was adopted at COP3 in 1997 [22]. Article 3 of the Kyoto Protocol set a target of reducing emissions from Annex I parties by 5% – relative to 1990 levels – come 2012 [22]. The achievement of this collective target would require each Annex I party to meet a Quantified Emission Limitation or Reduction Objective (QELRO), which imposed a cap upon their individual greenhouse gas emissions [19,22]. In most instances, QELROs required countries to reduce their emissions in order to meet the collective 5% target [19,23,24].
However, 3 of the 37 Annex I parties which ratified the decision were only required to stabilise their emissions at 1990 levels, whilst another 3 parties were permitted to increase emissions up to a specified point [19,23,24]. The legacy of the Kyoto Protocol is complex: 27 of the 37 Annex I parties which initially ratified the Protocol did fulfill their QELRO commitments, yet global greenhouse gas emissions continued to rise beyond 2012 [25]. A range of explanations have been offered for this ongoing increase in emissions [26,27,28], but one key shortcoming of the Kyoto Protocol was that it was never ratified by the United States of America, then the world’s leading emitter of greenhouse gases, whose emissions rose by 14% between 1990 and 2008 [19,29,30].
Another issue with the Protocol was that QELROs were only set for Annex I parties, despite some non-Annex I parties – most notably China and India – being major emitters of greenhouse gases [30]. It was estimated that China’s emissions trebled and India’s emissions doubled between 1990 and 2008, rendering them the world’s first and third greatest emitters by the start of the 2010s [30]. The UNFCCC sought to address this by broadening the scope of emissions reduction commitments [19], beginning at COP13 in 2007 – ten years after the initial proposal of the Kyoto Protocol [29,30]. COP13 produced the Bali Action Plan, which outlined the methods by which both developed and developing countries could enhance climate mitigation efforts [19,31,32]. Article 1b.i of the Plan called for developed countries to make measurable emissions reduction commitments in line with the Kyoto Protocol and its QELROs, whilst Article 1b.ii encouraged developing countries to take Nationally Appropriate Mitigation Actions (NAMAs) with financial and technical support from developed countries [31,33].
Beyond mitigation, COP13 also saw the Adaptation Fund – a financing body for climate adaptation efforts – made operational [31,32]. The emissions reduction enhancements outlined by the Bali Action Plan were to be negotiated upon further over the coming two years, then enshrined in a new, legally-binding treaty at COP15 in 2009 [30,32]. Unfortunately, COP15 failed to deliver upon this intention [29,31]. At the conference, five parties – Brazil, China, India, South Africa and the United States of America – drafted a potential decision text for this treaty [31]. This draft text incorporated the emissions reduction commitments and NAMAs from the Bali Action Plan, called upon developed countries to mobilise $100 billion in climate finance annually for developing countries by 2020 and noted the need to limit global warming to 2OC above pre-industrial levels – in line with the recommendations of the IPCC’s Fourth Assessment Report (AR4) [31,34,35]. This draft text would come to be known as the Copenhagen Accord and it failed to garner enough support to be enacted, with only 139 parties agreeing to its contents [29,34]. Many developing countries – particularly small island developing states (SIDs), which are acutely vulnerable to climate change, despite bearing little historical responsibility for it [36] – considered the Accord to be insufficiently ambitious and a dereliction of duty by developed countries [19,29,31]. Attempts were made to salvage the Copenhagen Accord over the following years, but these attempts were met with failure [29].
It would not be until 2015 that a new, legally-binding climate treaty was successfully negotiated: the Paris Agreement [37]. Signed at COP21, the Paris Agreement was ratified by 195 of the UNFCCC’s 198 parties [38] – including China, India and the United States of America, three parties which had been instrumental in preventing or undermining previous treaties [29,31]. Under Article 2.1a of the Paris Agreement, parties commit to “holding the increase in the global average temperature to well below 2OC above pre-industrial levels” – and, ideally, to no more than 1.5OC above them [37]. Rather than mandating emissions reductions for specific parties, like the Kyoto Protocol had done, the Paris Agreement requires all parties – both developed and developing – to make voluntary emissions reduction commitments, which must be submitted to the UNFCCC and which can be reviewed by its members [37,38]. These commitments are called Nationally Determined Contributions (NDCs) and constitute guidelines for their party’s domestic climate policies [37,38].
New NDCs are to be submitted by each party every five years, with Article 4.3 of the Agreement mandating that each round of new NDCs “will represent a progression” beyond the previous one [37,38]. The efficacy of Article 4.3 is reliant upon governments being pressured into more ambitious commitments by both the international community and their domestic constituents [38]. Early NDCs were criticised as being insufficiently ambitious; indeed, even if all parties had fulfilled the commitments included within their first round of NDCs, the global average temperature would still have risen an estimated 2.84OC above pre-industrial levels by 2100 [19,38,39]. Article 14 of the Paris Agreement creates an instrument designed to catalyse greater ambition: the Global Stocktake (GST) [37,40]. The GST serves as an assessment of parties’ collective progress under the Paris Agreement and is intended to provide guidance on increasing the ambition of their NDCs [37,40,41]. Article 14.2 of the Paris Agreement mandates that a GST shall be held every five years – with the first Global Stocktake scheduled to take place at COP28 in 2023 [37].
By Daniel Tucker-Bailey
Photos via Unsplash
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