In its judgment in Verein KlimaSeniorinnen Schweiz and Others v. Switzerland, the European Court of Human Rights (ECtHR) Grand Chamber ruled that Switzerland had acted insufficiently on climate change mitigation. This placed the Swiss senior women applicants at risk of climate harm, particularly from heatstroke, and breached their Article 8 rights to home and family life.
The Court held that states are obliged, under Article 8, to have an appropriate system of climate governance in place, consisting of a binding national regulatory framework and adequate subsequent implementation (549-550). Climate targets must form “an integral part” of this framework, with mitigation policy measures then used to meet them (549). According to the Court, states have a wide margin of appreciation in relation to the latter measures or means, but a reduced margin where the aims and objectives enshrined in targets are concerned (543, 549).
The Court effectively underscored the narrow margin of appreciation that states enjoy on targets by spelling out exactly what it expected them to be aiming for, rather than leaving it to their discretion. The Court stated that “effective respect for the rights protected by Article 8 of the Convention requires that each Contracting State undertake measures for the substantial and progressive reduction of their respective GHG emission levels, with a view to reaching net neutrality within, in principle, the next three decades” (548).
A key question that arises from this is whether one should read anything into the Court’s use of target destination language in its judgment. In this paragraph (548), it speaks in terms of states needing to have, as a floor or minimum, net neutral greenhouse gas (GHG) emissions by around 2050. Among policymakers (but not in the IPCC), this is called “climate neutrality”, involving not only CO2 but other GHGs, including nitrous oxide and methane. However, in other paragraphs in the judgment, the Court uses the language of “carbon neutrality” for targets (e.g. 547 and 250, where it prescriptively sets out what regulatory governance states must put in place to satisfy their positive obligations under Article 8). In scientific terms this means neutrality in emissions only in relation to carbon dioxide (CO2). Does this difference matter and, if so, why? Referring more than once to the latest findings of the Intergovernmental Panel on Climate Change (IPCC), did the Court understand the difference between the two? If it did, was it therefore intending to draw a distinction, so that when it says carbon neutrality it meant precisely that? Or did it misunderstand the difference and thus treat the two as interchangeable? Or did it perhaps understand it, but nevertheless treat the terms as interchangeable, not intending any distinction between them to be drawn for the purpose of the judgment? These are all important questions which we consider below.
Why does the difference matter? It matters scientifically because CO2 has different global warming characteristics to the other main greenhouse gases like methane. Of all the GHGs, CO2 is the main cause of global warming and is also where emissions reductions must be focused to first stabilise and then potentially also reduce global temperature again. It may be less potent as a GHG in an intensity sense than for example methane, but CO2 is much more long-lasting in the atmosphere and it accumulates. Those latter characteristic of CO2 matter because the human-caused CO2 emissions in the atmosphere since the industrial revolution are still there and continue to warm the planet, while methane is a short-lived climate forcer. That is why globally there is a “remaining carbon budget” (109-110) for 1.5 °C – the total net amount of CO2 that can still be emitted while keeping global warming to below this level – but not a ‘remaining GHG budget’.
The IPCC’s AR6 2023 Synthesis Report makes it clear that to limit warming to 1.5 °C requires reaching net zero CO2 by around 2050, followed by net negative CO2 emissions, but net zero GHG emissions only in the 2070s. The IPCC states that other GHGs like methane must still be strongly reduced in the short term to remain within 1.5 °C, but GHGs as a whole need only be reduced by 84% by 2050 (based on the GWP100 emissions metric to convert the global warming potential of non-CO2 gases into CO2 equivalents, as required by the Paris Agreement rulebook). While reaching and sustaining net-zero CO2 globally would halt the temperature increase, reaching and sustaining net-zero GHG emissions (calculated with the GWP100 metric) are projected to result in a gradual decline in surface temperature.
If courts are to base their judgments on the best available science, what do they therefore need to do? With an initial caveat that the IPCC’s net zero dates are based on integrated (socioeconomic and climate) assessment models (IAMs) which should not be treated like tablets of stone, the conclusion one might nevertheless draw from the science alone is that, for warming to be below 1.5 °C by 2100 (after a temporary overshoot of 1.5°C), courts need to ensure that states – on average – have in place and then deliver a target of net zero CO2 by 2050, but with net zero GHGs allowed to come later in the 2070s. But, to follow the science, courts also need to start ensuring that states have – on average – CO2 negative emissions targets from 2050 because, without that, the CO2 neutrality target year would have to be earlier, since the net-zero year 2050 stems from mitigation pathways that include a temporary overshoot of 1.5°C.
But of course one cannot simply look at IPCC-assessed pathways alone. What about the law on targets? Is international climate law more ambitious than that? Article 4(1) of the Paris Agreement states that, to keep within the long-term temperature goal of well below 2°C while pursuing efforts towards 1.5°C, parties must “aim to reach global peaking of greenhouse gas emissions as soon as possible, recognizing that peaking will take longer for developing country Parties, and to undertake rapid reductions thereafter in accordance with best available science, so as to achieve a balance between anthropogenic emissions by sources and removals by sinks of greenhouse gases in the second half of this century, on the basis of equity.” While the Article 4(1) legal target is couched in the language of climate neutrality, it is not obviously more ambitious than the mitigation pathways assessed by the IPCC. Mention of peaking of GHG emissions taking longer for developing countries and, towards the end of Article 4(1), “equity”, means that developed countries like Switzerland can be expected to have more ambitious targets to allow developing countries to have less ambitious ones. So legally, it does not mean that Switzerland can have a net zero GHGs target by as late as the 2070s.
And Switzerland does have a more ambitious target than this global average, as does the EU. The Swiss revised NDC target is described in the KlimaSeniorinnen judgment in terms of “GHG neutrality” (102) and “climate neutrality” (563) by 2050. The Swiss 2022 Federal Act on Climate Protection Goals, Innovation and Strengthening Energy Security implements this 2050 net zero target into domestic law, while also providing for net negative GHG emissions after 2050 (although no CO2 equivalent metric has been chosen by Switzerland yet). The European Climate Law, Regulation (EU) 2021/1119, is likewise aimed at achieving “climate neutrality” by 2050, and net-negative GHG emissions thereafter.
However, not all developed countries have 2050 climate neutrality targets. In its Climate Change Response Act, New Zealand for example, has set a 2050 net zero target for all GHG emissions other than biogenic methane, which has a separate target of a 24%-47% reduction in emissions by 2050 (the global average indicated in mitigation pathways assessed in the IPCC Special Report on 1.5°C in 2018). This is a country with a large methane-emitting ruminant livestock industry, where methane makes up more than 40% of their overall emissions.
What implications does all this have for human rights courts? Might courts in future cases be tempted to conclude, based on the above, that the EU and Switzerland have done more than the science suggests is needed for the protection of people’s human rights from climate change? After all, the science does not require net zero GHG reductions by 2050 for global average temperature to remain within 1.5 °C by 2100. We have seen though, that international law on climate change in the form of the Paris Agreement prevents courts from drawing that conclusion. Equity considerations mean that developed parties must do more than the science. Some may question whether New Zealand’s less ambitious GHG emissions targets sufficiently reflect that need for an equitable stepping-up. In Europe, might there be a danger that future national courts could interpret the ECtHR KlimaSeniorinnen judgment to require only the lesser carbon neutrality, stricto sensu? That is perhaps unlikely given that most European climate laws, like Switzerland’s, require GHG neutrality and states would be in breach of those in setting 2050 net neutral targets only for CO2 and not for all GHGs. As part of its assessment of whether a state is in breach of its human rights obligations, the ECtHR has long placed considerable emphasis on what a state has said it would do in its domestic law and if it has breached that commitment.
But in any event, human rights courts must deal with the present and not just with future targets. With temperature records currently being consistently broken, such courts should not be limiting themselves only to consideration of the Paris 1.5 °C temperature goal and future targets needed to stay or come back within it. As the Court made clear in the KlimaSeniorinnen judgment, we can expect risks to human rights to become worse if the 1.5 °C level is breached (usually defined as 20- or 30-year average), no matter whether permanently or – as featured in mitigation pathways assed by the IPCC – only temporarily. However, it is also clear from the experience of the applicants themselves, as well as many others globally, that extreme weather events such as heatwaves are already impacting human rights. States therefore have positive obligations to protect human rights at current levels of global warming, both in relation to mitigation and adaptation.
Returning to the questions posed earlier, it is difficult to know for certain to what extent the Grand Chamber in the KlimaSeniorinnen case appreciated the differences between carbon and GHG neutrality. On the one hand, the IPCC evidence it presents in the early part of the judgment (103-120) accurately reflects the IPCC’s references to reductions in CO2 and non-CO2 GHG emissions. However, it then seems odd not to see this clear differentiation carried through to the later, legally operative part of the judgment where climate and carbon neutrality are used interchangeably. That might lead one to conclude that the earlier material was somewhat cut and pasted without a thorough understanding of its implications. A more charitable view might point instead to the way those terms are commonly used interchangeably in other contexts and thus perhaps the ECtHR was simply doing the same, with no difference between the two terms intended. One might, for example, mention countries like the UK and Ireland setting national carbon budgets (and not GHG budgets) although striving for climate neutrality. They can be called that because the non-CO2 GHGs are included in the CO2-equivalent format. Perhaps the Court here was being similarly imprecise because it is common practice to conflate the two terms like this.
However, in future cases, both international and domestic courts should distinguish more clearly between CO2 and other GHGs. To an extent the current judgment has served a useful purpose by opening up this conversation for lawyers and policymakers. Everyone needs to be better aware that it is CO2 reductions that are key to preventing longer term warming. To that extent, the ECtHR may actually have been onto something in advocating for carbon neutrality. CO2 is where the main focus needs to be, albeit that wider GHG emissions reductions are also crucial for preventing harms to human rights from near-term warming. But the net-negative part from long term mitigation pathways assessed by the IPCC is also important. Having a 2050 net zero target is not enough to ensure human rights are protected. Globally, CO2 emissions must enter net-negative territory to ensure that protection. In supervising climate targets of developed countries with a high level of historical responsibility for climate change, like Switzerland, human rights courts at all levels therefore need to hold states not only to neutrality targets, but to insist that they aim for adequate levels of net-negative CO2 emissions , with a quantified target for those too. Without those net negative CO2 emissions, the world would need to be aiming at net-zero CO2 emissions in the first half of the 2030s, the time by when the latest IPCC Synthesis Report expects the 1.5 °C level to be reached.
The Court held that states are obliged, under Article 8, to have an appropriate system of climate governance in place, consisting of a binding national regulatory framework and adequate subsequent implementation (549-550). Climate targets must form “an integral part” of this framework, with mitigation policy measures then used to meet them (549). According to the Court, states have a wide margin of appreciation in relation to the latter measures or means, but a reduced margin where the aims and objectives enshrined in targets are concerned (543, 549).
The Court effectively underscored the narrow margin of appreciation that states enjoy on targets by spelling out exactly what it expected them to be aiming for, rather than leaving it to their discretion. The Court stated that “effective respect for the rights protected by Article 8 of the Convention requires that each Contracting State undertake measures for the substantial and progressive reduction of their respective GHG emission levels, with a view to reaching net neutrality within, in principle, the next three decades” (548).
A key question that arises from this is whether one should read anything into the Court’s use of target destination language in its judgment. In this paragraph (548), it speaks in terms of states needing to have, as a floor or minimum, net neutral greenhouse gas (GHG) emissions by around 2050. Among policymakers (but not in the IPCC), this is called “climate neutrality”, involving not only CO2 but other GHGs, including nitrous oxide and methane. However, in other paragraphs in the judgment, the Court uses the language of “carbon neutrality” for targets (e.g. 547 and 250, where it prescriptively sets out what regulatory governance states must put in place to satisfy their positive obligations under Article 8). In scientific terms this means neutrality in emissions only in relation to carbon dioxide (CO2). Does this difference matter and, if so, why? Referring more than once to the latest findings of the Intergovernmental Panel on Climate Change (IPCC), did the Court understand the difference between the two? If it did, was it therefore intending to draw a distinction, so that when it says carbon neutrality it meant precisely that? Or did it misunderstand the difference and thus treat the two as interchangeable? Or did it perhaps understand it, but nevertheless treat the terms as interchangeable, not intending any distinction between them to be drawn for the purpose of the judgment? These are all important questions which we consider below.
Why does the difference matter? It matters scientifically because CO2 has different global warming characteristics to the other main greenhouse gases like methane. Of all the GHGs, CO2 is the main cause of global warming and is also where emissions reductions must be focused to first stabilise and then potentially also reduce global temperature again. It may be less potent as a GHG in an intensity sense than for example methane, but CO2 is much more long-lasting in the atmosphere and it accumulates. Those latter characteristic of CO2 matter because the human-caused CO2 emissions in the atmosphere since the industrial revolution are still there and continue to warm the planet, while methane is a short-lived climate forcer. That is why globally there is a “remaining carbon budget” (109-110) for 1.5 °C – the total net amount of CO2 that can still be emitted while keeping global warming to below this level – but not a ‘remaining GHG budget’.
The IPCC’s AR6 2023 Synthesis Report makes it clear that to limit warming to 1.5 °C requires reaching net zero CO2 by around 2050, followed by net negative CO2 emissions, but net zero GHG emissions only in the 2070s. The IPCC states that other GHGs like methane must still be strongly reduced in the short term to remain within 1.5 °C, but GHGs as a whole need only be reduced by 84% by 2050 (based on the GWP100 emissions metric to convert the global warming potential of non-CO2 gases into CO2 equivalents, as required by the Paris Agreement rulebook). While reaching and sustaining net-zero CO2 globally would halt the temperature increase, reaching and sustaining net-zero GHG emissions (calculated with the GWP100 metric) are projected to result in a gradual decline in surface temperature.
If courts are to base their judgments on the best available science, what do they therefore need to do? With an initial caveat that the IPCC’s net zero dates are based on integrated (socioeconomic and climate) assessment models (IAMs) which should not be treated like tablets of stone, the conclusion one might nevertheless draw from the science alone is that, for warming to be below 1.5 °C by 2100 (after a temporary overshoot of 1.5°C), courts need to ensure that states – on average – have in place and then deliver a target of net zero CO2 by 2050, but with net zero GHGs allowed to come later in the 2070s. But, to follow the science, courts also need to start ensuring that states have – on average – CO2 negative emissions targets from 2050 because, without that, the CO2 neutrality target year would have to be earlier, since the net-zero year 2050 stems from mitigation pathways that include a temporary overshoot of 1.5°C.
But of course one cannot simply look at IPCC-assessed pathways alone. What about the law on targets? Is international climate law more ambitious than that? Article 4(1) of the Paris Agreement states that, to keep within the long-term temperature goal of well below 2°C while pursuing efforts towards 1.5°C, parties must “aim to reach global peaking of greenhouse gas emissions as soon as possible, recognizing that peaking will take longer for developing country Parties, and to undertake rapid reductions thereafter in accordance with best available science, so as to achieve a balance between anthropogenic emissions by sources and removals by sinks of greenhouse gases in the second half of this century, on the basis of equity.” While the Article 4(1) legal target is couched in the language of climate neutrality, it is not obviously more ambitious than the mitigation pathways assessed by the IPCC. Mention of peaking of GHG emissions taking longer for developing countries and, towards the end of Article 4(1), “equity”, means that developed countries like Switzerland can be expected to have more ambitious targets to allow developing countries to have less ambitious ones. So legally, it does not mean that Switzerland can have a net zero GHGs target by as late as the 2070s.
And Switzerland does have a more ambitious target than this global average, as does the EU. The Swiss revised NDC target is described in the KlimaSeniorinnen judgment in terms of “GHG neutrality” (102) and “climate neutrality” (563) by 2050. The Swiss 2022 Federal Act on Climate Protection Goals, Innovation and Strengthening Energy Security implements this 2050 net zero target into domestic law, while also providing for net negative GHG emissions after 2050 (although no CO2 equivalent metric has been chosen by Switzerland yet). The European Climate Law, Regulation (EU) 2021/1119, is likewise aimed at achieving “climate neutrality” by 2050, and net-negative GHG emissions thereafter.
However, not all developed countries have 2050 climate neutrality targets. In its Climate Change Response Act, New Zealand for example, has set a 2050 net zero target for all GHG emissions other than biogenic methane, which has a separate target of a 24%-47% reduction in emissions by 2050 (the global average indicated in mitigation pathways assessed in the IPCC Special Report on 1.5°C in 2018). This is a country with a large methane-emitting ruminant livestock industry, where methane makes up more than 40% of their overall emissions.
What implications does all this have for human rights courts? Might courts in future cases be tempted to conclude, based on the above, that the EU and Switzerland have done more than the science suggests is needed for the protection of people’s human rights from climate change? After all, the science does not require net zero GHG reductions by 2050 for global average temperature to remain within 1.5 °C by 2100. We have seen though, that international law on climate change in the form of the Paris Agreement prevents courts from drawing that conclusion. Equity considerations mean that developed parties must do more than the science. Some may question whether New Zealand’s less ambitious GHG emissions targets sufficiently reflect that need for an equitable stepping-up. In Europe, might there be a danger that future national courts could interpret the ECtHR KlimaSeniorinnen judgment to require only the lesser carbon neutrality, stricto sensu? That is perhaps unlikely given that most European climate laws, like Switzerland’s, require GHG neutrality and states would be in breach of those in setting 2050 net neutral targets only for CO2 and not for all GHGs. As part of its assessment of whether a state is in breach of its human rights obligations, the ECtHR has long placed considerable emphasis on what a state has said it would do in its domestic law and if it has breached that commitment.
But in any event, human rights courts must deal with the present and not just with future targets. With temperature records currently being consistently broken, such courts should not be limiting themselves only to consideration of the Paris 1.5 °C temperature goal and future targets needed to stay or come back within it. As the Court made clear in the KlimaSeniorinnen judgment, we can expect risks to human rights to become worse if the 1.5 °C level is breached (usually defined as 20- or 30-year average), no matter whether permanently or – as featured in mitigation pathways assed by the IPCC – only temporarily. However, it is also clear from the experience of the applicants themselves, as well as many others globally, that extreme weather events such as heatwaves are already impacting human rights. States therefore have positive obligations to protect human rights at current levels of global warming, both in relation to mitigation and adaptation.
Returning to the questions posed earlier, it is difficult to know for certain to what extent the Grand Chamber in the KlimaSeniorinnen case appreciated the differences between carbon and GHG neutrality. On the one hand, the IPCC evidence it presents in the early part of the judgment (103-120) accurately reflects the IPCC’s references to reductions in CO2 and non-CO2 GHG emissions. However, it then seems odd not to see this clear differentiation carried through to the later, legally operative part of the judgment where climate and carbon neutrality are used interchangeably. That might lead one to conclude that the earlier material was somewhat cut and pasted without a thorough understanding of its implications. A more charitable view might point instead to the way those terms are commonly used interchangeably in other contexts and thus perhaps the ECtHR was simply doing the same, with no difference between the two terms intended. One might, for example, mention countries like the UK and Ireland setting national carbon budgets (and not GHG budgets) although striving for climate neutrality. They can be called that because the non-CO2 GHGs are included in the CO2-equivalent format. Perhaps the Court here was being similarly imprecise because it is common practice to conflate the two terms like this.
However, in future cases, both international and domestic courts should distinguish more clearly between CO2 and other GHGs. To an extent the current judgment has served a useful purpose by opening up this conversation for lawyers and policymakers. Everyone needs to be better aware that it is CO2 reductions that are key to preventing longer term warming. To that extent, the ECtHR may actually have been onto something in advocating for carbon neutrality. CO2 is where the main focus needs to be, albeit that wider GHG emissions reductions are also crucial for preventing harms to human rights from near-term warming. But the net-negative part from long term mitigation pathways assessed by the IPCC is also important. Having a 2050 net zero target is not enough to ensure human rights are protected. Globally, CO2 emissions must enter net-negative territory to ensure that protection. In supervising climate targets of developed countries with a high level of historical responsibility for climate change, like Switzerland, human rights courts at all levels therefore need to hold states not only to neutrality targets, but to insist that they aim for adequate levels of net-negative CO2 emissions , with a quantified target for those too. Without those net negative CO2 emissions, the world would need to be aiming at net-zero CO2 emissions in the first half of the 2030s, the time by when the latest IPCC Synthesis Report expects the 1.5 °C level to be reached.