Working PaperPDF Available

The Paris Agreement global goals: What does a fair share for G20 countries look like?

Authors:

Figures

Content may be subject to copyright.
The Paris Agreement global goals: What does a fair share for G20 countries look like? 1
The Paris Agreement global goals: What does a fair share for G20 countries look like? 2
Cover photo: Lhelene and Petar Bean
Author: Yann Robiou du Pont
Date: 17 March 2017
Australian-German Climate & Energy College, The University of Melbourne
700 Swanston Street, Lab 14, Level 1,
3010 Parkville, Melbourne, Victoria, Australia
Contact: yann.rdp@climate-energy-college.org
The Paris Agreement global goals: What does a fair share for G20 countries look like? 3
The Paris Agreement, entered into force since 4 November 2016, has set ambitious global goals to avoid
dangerous climate change impacts. These global goals include an emissions goal of net-zero emissions in
the second half of the century, and two temperature goals: limiting global warming to well below 2 °C and
to pursue efforts to 1.5 °C.
The national emissions mitigation pledges are collectively insufficient to achieve the Paris Agreement goal
of limiting global warming to well below 2 °C, let alone 1.5 °C (UNFCCC 2015c; Rogelj et al. 2016; Robiou
du Pont, Jeffery, Gutschow, et al. 2017). A global stocktake process is organised under the United Nations
to deliver successive increase in ambition of national contributions and meet the Paris Agreement goals
equitably.
This report reviews the literature to compare the socio-economic implications and climate impacts of
achieving each of the Paris Agreement temperature goals: 1.5 °C and 2 °C. Drawing on a recent publication
in Nature Climate Change (Robiou du Pont, Jeffery, Gütschow, et al. 2017) and its related website
www.Paris-equity-check.org, this report then examines the scenarios to reduce greenhouse-gases (GHG)
emissions consistent with the Paris global goals.
Finally, this report presents greenhouse-gases (GHG) emissions targets for G20 members consistent with
the five effort sharing categories contained in the latest report of the Intergovernmental Panel on Climate
Change (IPCC), and compares the equity performances of their climate pledges against their own
declarations on equity.
The Paris Agreement global goals: What does a fair share for G20 countries look like? 4
At the global level:
In 2030, global GHG annual emissions should reduce to 32.6 GtCO2eq to align with the average
of emissions scenarios consistent with a higher than 50% chance to return to 1.5 °C in 2100.
Emissions levels consistent with a likely (>66%) chance to meet the 2 °C goal average at 39.7
GtCO2eq in 2030
Net-zero emissions should be achieved between 2059 and 2087 for 1.5 °C in 2100, and from
2080 for 2 °C
Annual emissions mitigation rates reach similar maxima under both temperature goals, 2.3%/y
towards 1.5 °C compared to 2.1%/y towards 2 °C
The only emissions scenarios from the IPCC database consistent with the Paris Agreement and
with emissions peaking in 2030, have unrealistic aerosols concentrations
At the national level:
The pledges of the G20 members are collectively insufficient to meet any concept of equity
Collectively, G20 pledges for 2030 should be lower by 39 percent (of 2010 levels) to align with
the average of the five equity concepts under the 2 °C goal, and 63 percentage lower under the
1.5 °C goal
The G20 can close the 2030 mitigation gap towards 2 °C and considerably reduce the gap
towards 1.5 °C by adopting the average of the five equity allocations
Brazil and Mexico are the most ambitious countries towards the 2 °C goal with pledges within
the range of four out of five equity concepts, followed by the EU whose 2030 pledge is within
the range of three equity allocations
The pledges of Russia, China, Turkey and Saudi Arabia are weaker than any equity concept
The Paris Agreement global goals: What does a fair share for G20 countries look like? 5
Executive summary ....................................................................................................................................... 2
Key findings ............................................................................................................................................... 4
1. The Paris long-term global goals ........................................................................................................... 6
1.1 Lead-up to the Paris long-term global goals ....................................................................................... 6
1.2 The impacts of a 2 °C or 1.5 °C warmer world .................................................................................... 7
1.3 Global emissions scenarios to reach the climate goals ...................................................................... 9
2. Equitable G20 contributions towards achieving the Paris Global Goals............................................. 12
2.1 Ratchetting-up global ambition ........................................................................................................ 12
2.2 Equity under the UNFCCC ................................................................................................................. 12
2.3 Distributing emissions equitably ....................................................................................................... 12
2.4 Results for G20 countries .................................................................................................................. 13
2.5 Consistency of equity performance with statements on fairness .................................................... 18
Conclusions ................................................................................................................................................. 20
Acknowledgements ..................................................................................................................................... 20
References .................................................................................................................................................. 21
The Paris Agreement global goals: What does a fair share for G20 countries look like? 6
1.1 Lead-up to the Paris long-term global goals
The anthropogenic influence on climate through greenhouse gas (GHG) emissions has been identified for
decades
i
. The international community has gradually taken note of these results and commissioned
scientific research to assess the impacts of climate change and identify mitigation measures.
The United Nations (UN) and the World Meteorological Organization established, in 1988, an
intergovernmental scientific body, the Intergovernmental Panel on Climate Change (IPCC), with the
mission to provide the international community with an impartial scientific assessment of climate change
and its impacts
ii
. In its first assessment report (AR) two years later, the IPCC called for a global treaty on
anthropogenic GHG emissions. Following this call to coordinate collective action on climate change, the
international community created in 1992 the UN Framework on Climate Change Convention (UNFCCC).
The objective of this Convention included the first long-term global goal of a ‘stabilization of greenhouse
gas concentrations in the atmosphere at a level that would prevent dangerous anthropogenic interference
with the climate system’ (UNFCCC 1992).
With the continuous increase of global emissions and the acceleration of global warming
iii
, it became
urgent to decide on a level to stabilise GHG concentrations in order to prevent dangerous climate impacts.
Informed by the IPCC’s second and third assessment reports, the UNFCCC adopted in 2010 a global
warming limit of 2 °C compared to pre-industrial levels. Meeting the 2 °C threshold already represents an
economic challenge and current national pledges are insufficient to stay below this limit. However, this 2
°C threshold may be inadequate to avoid dangerous global warming impacts. Indeed, climate impacts are
distributed unevenly around the globe and affect vulnerable countries the most. Even a 2 °C warming
represents major risks, sometimes existential, for many countries.
As a result, a group of 101 countries called for a 1.5 °C warming limit for the first time at the 15th
Conference of the Parties (COP) in Copenhagen in 2009
iv
. Finally, last year, the Paris Agreement
strengthened the 2 °C objective with a commitment to limit warming to ‘well below 2°C’ and to ‘pursue
efforts to limit […] to 1.5 °C’. The Agreement also added the objective of reaching net-zero GHG emissions
in the second half of the century. The global goals of the Paris Agreement have been saluted both in the
negotiation venue and in the subsequent literature (Schellnhuber, Rahmstorf, and Winkelmann 2016;
Rogelj and Knutti 2016).
i
See: www.theguardian.com/business/2016/apr/13/climate-change-oil-industry-environment-warning-1968
ii
See: hbigpicture.unfccc.int/#content-the-convention-timeline
iii
See: openclimatedata.net/climate-spirals/concentration-temperature
iv
See: http://climateanalytics.org/hot-topics/1-5c-key-facts.html
The Paris Agreement global goals: What does a fair share for G20 countries look like? 7
Figure 1 | Key dates towards the Paris Agreement long-term global goals and near-term IPCC agenda.
1.2 The impacts of a 2 °C or 1.5 °C warmer world
Success in the pursuit of the 1.5 °C goal will depend on the estimated climate impacts of not reaching this
goal versus the socio-economic costs incurred to attain it. While the implications of limiting global
warming to 2 °C are well researched, in particular since the Copenhagen Accord in 2009, little scientific
literature is available both on the economic requirements and on the climate impacts implied by the 1.5
°C goal. In order to fill that knowledge gap and not to miss the rapidly fading opportunity to limit warming
to 1.5 °C (Rogelj et al. 2013), the UNFCCC has invited the IPCC to provide a special report in 2018 (Fig. 1)
on the impacts of a 1.5 °C warming and related GHG emissions pathways (COP21 decision (UNFCCC
2015a)).
Two years is a very short period to research, write, review and publish new results that should then be
gathered and put together in this special IPCC report. Fortunately, some studies have already identified
specific climate risks that increase with global warming. The Fifth Assessment Report of the IPCC (IPCC
AR5) states that while the risks of ‘large-scale singular events’ and of ‘global aggregate impacts’ do not
differ significantly under a 1.5 °C or 2 °C world, the risks on ‘unique and threatened systems’, the risk of
‘extreme weather events’ and the ‘distribution of impacts’ increase from ‘moderate’ to ‘high’ (Fig. 2,
reproduced from IPCC-AR5 WGII-Fig. 19-4). While no cost-estimate of the corresponding climate impacts
is available, limiting warming to 1.5 °C would offer a greater chance to avoid costly climate impacts.
The Paris Agreement global goals: What does a fair share for G20 countries look like? 8
Figure 2 (reproduced from IPCC-AR5 WGII-Fig. 19-4) | The dependence of risk associated with the Reasons for Concern (RFCs)
on the level of climate change
v
.
More recent work (Schleussner, Lissner, et al. 2016; Schleussner, Rogelj, et al. 2016) specifically studied
the impacts expected at 1.5 °C and 2 °C on a selection of indicators. For example, the likelihood of a pre-
industrial 1-in-a-1000 day extreme-temperature event is 27 times higher in a 2 °C warmer world than pre-
industrial levels (Fischer and Knutti 2015; Schleussner, Rogelj, et al. 2016). This probability is halved in a
1.5 °C warmer world than in a 2 °C one. While the uncertainty associated with precipitation is considerably
v
Figure 2 reproduced from IPCC-AR5 WGII, Fig. 19-4, p.1073, from Oppenheimer, M., M. Campos, R. Warren, J. Birkmann, G. Luber, B.C. O’Neill,
and K. Takahashi, 2014: Emergent risks and key vulnerabilities. In: Climate Change 2014: Impacts, Adaptation, and Vulnerability. Part A: Global
and Sectoral Aspects. Contribution of Working Group II to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change [Field,
C.B., V.R. Barros, D.J. Dokken, K.J. Mach, M.D. Mastrandrea, T.E. Bilir, M. Chatterjee, K.L. Ebi, Y.O. Estrada, R.C. Genova, B. Girma, E.S. Kissel, A.N.
Levy, S. MacCracken, P.R. Mastrandrea, and L.L. White (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA.
Full legend: “The dependence of risk associated with the Reasons for Concern (RFCs) on the level of climate change, updated from the Third
Assessment Report and Smith et al. (2009). The color shading indicates the additional risk due to climate change when a temperature level is
reached and then sustained or exceeded. The shading of each ember provides a qualitative indication of the increase in risk with temperature for
each individual ‘reason.’ Undetectable risk (white) indicates no associated impacts are detectable and attributable to climate change. Moderate
risk (yellow) indicates that associated impacts are both detectable and attributable to climate change with at least medium c onfidence, also
accounting for the other specific criteria for key risks. High risk (red) indicates severe and widespread impacts, also accounting for the other
specific criteria for key risks. Purple, introduced in this assessment, shows that very high risk is indicated by all specific criteria for key risks.
Comparison of the increase of risk across RFCs indicates the relative sensitivity of RFCs to increases in GMT. In general, assessment of RFCs takes
autonomous adaptation into account, as was done previously (Smith et al., 2001, 2009; Schneider et al., 2007). In addition, this assessment took
into account limits to adaptation in the case of RFC1, RFC3, and RFC5, independent of the development pathway. The rate and timing of climate
change and physical impacts, not illustrated explicitly in this diagram, were taken into account in assessing RFC1 and RFC5. Comments
superimposed on RFCs provide additional details that were factored into the assessment. The levels of risk illustrated reflect the judgments of
Chapter 19 authors.Available at: www.ipcc.ch/pdf/assessment-report/ar5/wg2/WGIIAR5-Chap19_FINAL.pdf
The Paris Agreement global goals: What does a fair share for G20 countries look like? 9
greater, the likelihood of extreme precipitation is expected to rise globally with warming temperatures
(Schleussner, Lissner, et al. 2016), and in South-Asia in particular. At the same time, the water availability
is expected to decrease locally. The water availability in the Mediterranean region should decrease by 9%
under a 1.5 °C warming, and by 17% under a 2 °C warming. With a 2 °C warming, all coral reefs are at risk
of long-term degradation (K Frieler et al. 2012). Limiting warming to 1.5 °C is expected to save a fraction
of the world’s corals from degradation linked with bleaching events. Multi-millennial sea-level rise also
has significant differences under a 1.5 °C or 2 °C warmer world (Levermann et al. 2013) and sea-level rise
projections until 2300 strongly depend on emissions trajectories (Nauels et al. 2016). Yields of maize,
wheat, rice and soy in tropical regions are projected to decrease with global warming. Nevertheless, the
increasing concentration of CO2 in the atmosphere attenuates the yield loss for maize and wheat, and
even leads to a yield increase for rice and soy (Schleussner, Lissner, et al. 2016). Overall, the negative
effects on the economy grow with global warming (Burke, Hsiang, and Miguel 2015).
1.3 Global emissions scenarios to reach the climate goals
Reaching a temperature goal at minimal costs implies an optimal selection and deployment of low-carbon
options (e.g. policies, renewable energies, afforestation, reduction of consumption, recycling…). The costs
and effects, as well as the timing of these options are modelled using Integrated Assessment Models
(IAMs). An IAM derives the implementation of the cost-optimal options and a global scenario of
anthropogenic GHG emissions usually throughout the 21st century (see box ‘Emissions scenarios vs.
carbon budgets’ below). Multiple research groups have developed IAMs following different assumptions
and explored a range of possible temperature outcomes. The analyses presented in the latest IPCC report
are based on 846 scenarios
vi
. Some of these emissions trajectories decrease rapidly and become negative
soon after mid-century. On the other hand, some emissions scenarios rise steadily and reflect business-
as-usual trajectories in the absence of any climate policy. The temperature likelihood response to 524 of
these 846 scenarios
vii
was projected using the simple carbon cycle and climate model MAGICC6 (M.
Meinshausen, Raper, and Wigley 2011).
Among the 846 scenarios used in the IPCC AR5, 155 have negative emissions in 2100, and 40 of these have
a likely (>66%) chance to contain global warming below 2 °C until 2100. Only two scenarios also feature a
more likely than not (>50%) chance of returning to below 1.5 °C of warming in 2100. Since the publication
of the IPCC AR5, a study (Rogelj et al. 2015) analysed the sectoral characteristic of 37 additional scenarios
consistent with 1.5 °C.
According to this study, reaching the emissions levels consistent with the 1.5 °C goal requires immediate
action and a faster scale-up of lower carbon measures (Rogelj et al. 2015). The differences in solutions to
curve emissions from 2 °C trajectories to 1.5 °C ones are summarised in Table 1 (adapted from Rogelj et
al. (2015)). Most importantly, lower energy demand and efficiency improvements, which substantially
reduce the mitigation costs, are a key enabling factor of the 1.5 °C goal. A large-scale deployment of
Carbon Dioxide Removal is another requirement. Overall, costs associated with limiting warming to 1.5 °C
are twice higher than to 2 °C over the century, and even greater in the near term. However, the results of
the study do not account for economic benefits of mitigating emissions towards 1.5 °C. Such co-benefits
(for example: avoided climate impacts (Katja Frieler et al. 2016), reduced air pollution and improved
energy security) represent an important driver for emissions reduction (Averchenkova, Stern, and
Zenghelis 2014).
vi
The database is hosted at: tntcat.iiasa.ac.at/AR5DB/
vii
Data visualization available at: www.pik-potsdam.de/primap-live/ar5-scenario-explorer/
The Paris Agreement global goals: What does a fair share for G20 countries look like? 10
Carbon (CO2) budgets are often associated with climate objectives. Due to the long lifetime of CO2 in the
atmosphere, the temperature at the end of the century depends on the cumulative CO2 emissions rather
than on the timing of those CO2 emissions. A linear relationship links the cumulative CO2 emissions to the
maximal temperature over the century (IPCC 2014).
Using carbon budgets allows us to understand how national budgets change according to temperature
goals. However, using carbon budgets do not provide information on the least-cost measures and their
timing to achieve the CO2 mitigation. By contrast, greenhouse-gases (GHG) emissions scenarios from
Integrated Assessment Models are associated with specific policies and technology deployment that
minimise the emissions mitigation costs. Another advantage of using multi-gas emissions scenarios to
derive national allocations is that countries' mitigation measures can be assessed not just for CO2, but for
all the main greenhouse-gases (as defined in the Kyoto-Protocol
viii
: methane, nitrous oxide…).
Table 1 | Comparison of the characteristics of scenarios limiting global warming to either 2 °C or 1.5 °C
ix
.
Demand
Global energy demand in 1.5 °C scenarios remains less than 40% above 2010 levels over the 21st century, and not more
than 15% in most scenarios.
Technologies
In 2030, the contribution of low-carbon technologies in the electricity sector (renewable, nuclear, Carbon Capture and
Storage) is 10% higher for 1.5 °C scenarios than for 2 °C. The transport sector has a similar share of electricity use for 1.5
°C and 2 °C scenarios, about 25% in 2050 (compared to 1% in 2013). In the industrial, transport and buildings (residential
& commercial) sectors, emissions in 2050 are about 25%, 40% and 50% lower in 1.5 °C scenarios than in likely 2 °C
scenarios, respectively.
Non-CO2 gases
The full mitigation potential of non-CO2 gases is reached for 2 °C scenarios. The additional mitigation towards 1.5 °C
scenarios mainly arises from additional CO2 mitigation.
Carbon Dioxide
Removal
Carbon Dioxide Removal (CDR) compensates 60% to 85% of the total fossil fuel CO2 emissions over the 2010-2100 period
under 1.5 °C scenarios, but only less than half under 2 °C scenarios. Large scale deployment of CDR technologies are a
requirement of these 1.5 °C scenarios.
Costs
Mitigation costs aggregated throughout the 21st century are up to twice as high for 1.5 °C scenarios than for 2 °C.
Relatively, near-term costs are even greater.
The scenarios selected from the IPCC AR5 database and from the study on the 1.5 °C goal can be
categorised based on their compatibility with the Paris Agreement goals: (i) 32 scenarios with emissions
peaking by 2020, (ii) 39 peaking by 2020 with a more likely than not (>50%) chance of returning to 1.5 °C
in 2100, (iii) 6 scenarios peaking in 2030 (Fig. 3). The current national commitments for 2030 add up to a
global level of 52.5 GtCO2eq (the average of the ‘high-ambition’ and ‘low-ambition’ estimates (Malte
Meinshausen and Alexander 2015) of 49.4 GtCO2eq and 55.6 GtCO2eq respectively), which is higher than
the historical levels of 47.2 GtCO2eq of 2010 (Fig. 3).
Only six emission scenarios in line with the 2 °C objectives can peak as late as 2030, and reach 2030 levels
(56.3 GtCO2eq in average) compatible with the current aggregate commitments. However, these delayed
action scenarios (all from a unique model) are only loosely consistent with the Paris Agreement as their
assumed aerosol emissions are outside the ranges consistent with the underlying CO2 path (Rogelj et al.
2014). Moreover, these scenarios’ emissions do not peak as soon as possible, as defined in Article 2 of the
Paris Agreement.
viii
The definition of the Kyoto greenhouse gases is available at: unfccc.int/resource/docs/convkp/kpeng.pdf
ix
adapted from Rogelj et al. (2015).
The Paris Agreement global goals: What does a fair share for G20 countries look like? 11
Delaying the peaking of global emissions results implies steeper and more costly mitigation beyond 2030.
Indeed, peaking global emissions no sooner than 2030 results in maximal annual mitigation rates over the
21st century of 3.5%/y from 2040 to 2050 (and 3.2%/y in average over the 2030-2050 period) (Robiou du
Pont, Jeffery, Gütschow, et al. 2017). On the other hand, starting mitigation towards 2 °C by 2020 results
in maximum annual mitigation rate of only 2.1%/y in 2025 (and 1.6%/y in average over 2030-2050). The
2 °C scenarios with pre-2020 peaking have an average level of 39.7 GtCO2eq in 2030, which is almost equal
to the 40 GtCO2eq emissions goal of the Paris decision (UNFCCC 2015a). Finally, emissions scenarios
towards 1.5 °C average at 32.6 GtCO2eq in 2030 and have a maximal annual mitigation rate of 2.3%/y in
2039 (and 2.2%/y in average over 2030-2050). Following 2 °C implies net-zero emissions as early as 2080,
while 1.5 °C scenarios become negative between 2059 and 2087.
Figure 3 | Global emissions consistent with the Paris Agreement compared to current aggregated pledges. IAM scenarios
consistent with the Paris Agreement, including emissions from the land-use sector and international aviation and shipping, and
their average (thicker lines) under the 1.5 °C goal (orange) or the 2 °C goal with emissions peaking by 2020 (blue) or in 2030
(purple). Scenarios consistent with the 2030 Paris decision target (green circles) are more opaque. The selected scenarios are
shown with all scenarios from the IPCC AR5 database (grey lines, panel inset). Estimated historical emissions (Nabel et al. 2011)
are shown until 2015 (black line).
The Paris Agreement global goals: What does a fair share for G20 countries look like? 12
2.1 Ratchetting-up global ambition
In the decision to adopt the Paris Agreement, the international community recognised the inadequacy of
the current pledges with the least-cost scenarios consistent with its objectives (UNFCCC 2015a). The Paris
Decision indeed includes a 2030 global indicative target of below 40 GtCO2eq scientifically consistent with
cost-optimal pathways selected to limit warming to 2 °C (Robiou du Pont, Jeffery, Gütschow, et al. 2017).
Moreover, this indicative target is in line with recent 42 GtCO2eq recommendation from the UNEP (2015)
and the 40 GtCO2eq of a recent study (Malte Meinshausen et al. 2015, Supplementary information,
Section 2). The identification of a 2030 target consistent with the 1.5 °C goal will be based on the upcoming
IPCC special report on 1.5 °C to be published in 2018. In order to ratchet-up global ambition, the Paris
Agreement binds countries to periodically take stock, starting in 2018, ‘in light of equity and the best
available science’ (UNFCCC 2015a), and each country’s successive pledge will represent a progression.
However, UNFCCC Parties have not operationalised equity at the country level and the Paris Agreement
only contains global quantified emissions objectives. The determination of equitable national emissions
targets that add up to cost-optimal scenarios consistent with the Paris Agreement can inform the process
of ratchetting-up global ambition.
2.2 Equity under the UNFCCC
The principles of equity contained in the Paris Agreement were first outlined in the UNFCCC treaty where
all countries agreed to share global mitigation efforts following their ‘common but differentiated
responsibilities and respective capabilities’ (CBDR-RC) (UNFCCC 1992). The Convention allocates
differentiated commitments to specific countries that should lead climate change mitigation and provide
financial support to developing countries.
In the lead up to the Paris Agreement, rather than negotiating binding differentiated mitigation targets,
countries agreed to submit their (Intended) Nationally Determined Contributions (I)NDCs. Each country
determines its level of emissions mitigation guided by its own perception of its national circumstances
and of its own interpretation of CBDR-RC. The ensuing Paris Agreement does not refer to explicit groups
of countries, but rather binds each country to communicate successive NDCs with the ‘highest ambition’
reflecting its CBDR-RC interpretation. The Agreement still requests developed countries, without naming
these, to take the lead in reducing emissions economy-wide and mobilising climate finance. The absence
of consensus on an effort-sharing approach resulted in a bottom-up situation whereby countries
determine their own mitigation targets. The aggregation of the current pledges is inconsistent with the
identified least-cost mitigation scenarios.
2.3 Distributing emissions equitably
The IPCC AR5 presented five categories of burden sharing (Edenhofer et al. 2014). A recent study (Robiou
du Pont et al. 2016) followed these categories to derive an equity framework that allocates the emissions
of cost-optimal mitigation scenarios across countries. This framework, applied to the cost-optimal
scenarios selected to meet the Paris Agreement goals of 2 °C or a 1.5 °C, provides national emissions
pathways consistent with five equity approaches representative of the five IPCC equity categories:
‘capability’, ‘equal per capita’, ‘Greenhouse Development Rights’, ‘equal cumulative per capita’ and
‘constant emissions ratio’ (Table 2).
The Paris Agreement global goals: What does a fair share for G20 countries look like? 13
Table 2 | Description of the emissions allocation approaches.
Colour
Allocation name
Code
IPCC categoryx
Allocation characteristics
Capability
CAP
Capability
Countries with high GDP per capita have low emissions allocations.
Equal per capita
EPC
Equality
Convergence towards equal annual emissions per person in 2040.
Greenhouse
Development
Rights
GDR
Responsibility-
capability-need
Countries with high GDP per capita and high historical per capita
emissions have low emissions allocation. This approach preserves a
‘right to development’ through the allocation of mitigation
requirements (Baer et al. 2008; Kemp-Benedict 2010; Malte
Meinshausen et al. 2015).
Equal cumulative
per capita
CPC
Equal cumulative per
capita
Populations with high historical emissions have low emissions
allocations.
This approach allocates to each country total cumulative emissions
proportional to its cumulative population over the 1990-2100 period.
Constant
emissions ratio
CER
Staged approaches
Maintains current emissions ratios, preserves status quo.
This approach, often referred to as the ‘grandfathering’, is generally not
considered as an equitable option in climate justice (Caney 2009) and
not supported as such by any Party.
The 'capability' (CAP) approach allocates to each country a share of global emissions proportional to its
population divided by its per capita GDP or proportional to its GDP when global net emissions become
negative. The 'equal per capita' (EPC) derives national shares of global emissions that are proportional to
each country's population. The 'Greenhouse Development Rights' (GDR) approach reflects the
'responsibility-capability-need' IPCC category, and issues emissions allocations based on historical
emissions, projected business-as-usual emissions, population and wealth distribution of each country
(Baer et al. 2008). The 'equal cumulative per capita' (CPC) approach allocates country with total
cumulative emissions proportional to its cumulative population over a given period. Finally, the 'constant
emissions ratio' (CER) approach reflects preserves the current (as of 2010) shares of global emissions
across countries. This grandfathering approach is often considered less equitable than other approaches
found in the literature (Caney 2009; Peters et al. 2015). The national emissions allocations derived under
this framework do not include emissions from international shipping and aviation or emissions from the
land-use sector for which accounting rules differ widely across countries.
2.4 Results for G20 countries
The G20 includes 20 of the world’s largest economies: 19 countries and the European Union (EU). In this
paper, the G20 includes 44 countries with the 28 EU members that are represented by the European
Commission and negotiate as a group under the UNFCCC. Together, the G20 emitted around 76% of global
emissions in 2010 over 74% when including land-use emissions (Gütschow et al. 2016). Domestic
mitigation action from the G20 can therefore have a crucial impact on climate change. Moreover, with
78% of the global Gross Domestic Product (GDP) (World Bank 2014), the G20 has the capacity to fund and
lead international action to achieve the Paris Agreement goals. Following the communique of the latest
G20 summit in Hangzhou calling for an entry into force of the Paris Agreement as soon as possible, a rapid
ratification of G20 members enabled the Paris Agreement to become effective in less than a year. Off the
G20 members, only Russia and Turkey have not yet ratified the agreement the European Union has
ratified, but not all its members
xi
.
x
See Table 6.5 and Fig. 6-28 of the IPCC-AR5 WGIII at: www.ipcc.ch/pdf/assessment-report/ar5/wg3/ipcc_wg3_ar5_chapter6.pdf
xi
See: unfccc.int/paris_agreement/items/9444.php
The Paris Agreement global goals: What does a fair share for G20 countries look like? 14
Looking at the current G20 mitigation ambition under the 2 °C goal, the aggregated (I)NDCs of the G20
members appear inconsistent with any of the equity approaches (Fig. 4). The mitigation gap with 1.5 °C
equitable pathways is therefore even greater. Collectively, the G20 should reach net zero-emissions
between 2065 and 2083 depending on the equity concept, in average over the 2 °C scenarios (Fig. 4), and
between 2050 and 2075 over 1.5 °C scenarios.
Note that the national equitable emissions pathways presented in this report can be met under a
combination of domestic mitigation, internationally traded emissions mitigation (UNFCCC 2015b) or
financial support towards global mitigation (Robiou du Pont, Jeffery, Gütschow, et al. 2017).
Figure 4 | Comparison of the G20 equitable emissions pathways under the 2 °C scenarios with the aggregation of their
(I)NDCs. Emissions allocations, excluding land-use and bunker emissions, under five equity allocation representative of the five
IPCC categories are compared the G20 sum of (I)NDCs average (black circles) and range (vertical black line). Coloured patches
and lines show allocation ranges and averages, respectively, over global 2 °C scenarios.
By definition, combining multiple visions of equity using weighting factors (Raupach et al. 2014) or a
leadership based approach (Malte Meinshausen et al. 2015) does not correspond to any vision of equity
but can represent a political compromise (Raupach et al. 2014), and is useful to compare national
allocations under different temperature goals. To reach the 1.5 °C goal rather than the 2 °C goal, the G20
should reduce its 2030 emissions by an additional 24 percentage point of 2010 levels, in average over the
five equity allocations, (Fig. 5a). This additional collective of G20 members reduction towards the 1.5 °C
goal is comparable, in percent of 2010 levels, to that of the G8+China as a group or as individual Parties
(Fig. 5a and Robiou du Pont et al. (2017)). Non-G20 countries’ collective emissions, but also India’s
emissions, should be around 45 percentage-points lower in 2030 to reach the 1.5 °C goal compared to the
2 °C goal.
The Paris Agreement global goals: What does a fair share for G20 countries look like? 15
Comparing current (I)NDCs to the average of the five equity allocations, the G20 (I)NDCs should be 39
percentage-points lower collectively to align with the 2 °C goal. In contrast, non-G20 countries collectively
overachieve the average of their allocations by 27 percentage-points (Fig. 5b). Turkey’s INDC should be
143 percentage-points lower than currently, Saudi Arabia’s NDC 134 percentage-points, Russia’s INDC 71
percentage-points and China’s NDC 61 percentage points lower to align with average 2 °C allocations.
v
Figure 5 | Comparisons of G20 countries’ emissions allocations under the 1.5 °C or 2 °C goals and with their (I)NDCs. a.
Comparison of 1.5 °C and 2 °C allocations averaged over the five equity approaches in 2030 (as a percent change to 2010 levels).
b, Comparison of 2 °C allocations averaged over the five equity approaches with (I)NDCs in 2030 (as a percent change to 2010
levels). Disk sizes are proportional to 2010 emissions levels. Colours indicate world regions. Aggregated results for G20 countries
(larger disk) and the rest of the world (‘Non-G20’, smaller disk) are shown in grey.
The gap between conditional (I)NDCs (‘high-ambition’ assessment of Malte Meinshausen and Alexander
(2015)) and 2 °C consistent pathways could be closed if the G8 and China together adopt the average of
the five equity approaches (Robiou du Pont, Jeffery, Gütschow, et al. 2017). If the G20 countries
collectively adopt the average of the five approaches, the gap between conditional (I)NDCs and 1.5 °C
consistent pathways could almost be closed (Fig. 6). The rest of the world (Non-G20 countries), would
then only have to collectively reduce emissions by 510 MtCO2eq, compared to their conditional (I)NDCs,
to meet the average of their five allocations towards 1.5 °C.
The Paris Agreement global goals: What does a fair share for G20 countries look like? 16
Figure 6 | Gaps between equitable emissions allocations and conditional (I)NDCs in 2030. Countries following individual
approaches (tip of coloured patches), or the average of the five approaches (white lines) under the 2°C (left) or 1.5°C goals (right),
reduce or increase the projected 2030 global emissions levels (excluding LULUCF and bunker emissions) compared to aggregated
conditional (I)NDCs. The global gaps (grey arrow) between current aggregated conditional (I)NDCs and the average of global
scenarios consistent with the Paris 2°C or 1.5°C goals (grey bar) are shown in each panel.
The Paris Agreement global goals: What does a fair share for G20 countries look like? 17
At the national level, the consistency of (I)NDCs with the five equity approaches varies greatly across G20
members (Fig. 7)
xii
. The INDC of Turkey, and the NDCs of Saudi Arabia, Russia and China imply 2030
emissions level much higher than any equity allocations, even under the 2 °C goal.
Considering the 2 °C goal, the most ambitious Parties are Brazil and Mexico whose NDCs are within the
ranges of four equity allocations, followed by the EU whose NDC is within the range of three equity
allocations. Under the 1.5 °C perspective, Australia’s NDC is within the range of two equity allocations (a
grandfathering approach and the GDR that uses contentious business-as-usual projections), and
Indonesia’s NDC is within the range of the equal cumulative per capita approach and just within the range
of the equal per capita approach.
Figure 7 | Comparison of equitable 2030 emissions allocations of G20 members with their respective 2030 (I)NDCs assessment
under the 2 °C and 1.5 °C goals. Emissions allocations in 2030, excluding land-use and bunker emissions, under five equity
allocations representative of the five IPCC categories are compared with countries’ (I)NDC averages (dashed black line). Emissions
ranges of any colour represent countries’ allocation range under the 1.5 °C (left) and 2 °C (right) goals.
xii
Results of all countries can be visualised and downloaded at Paris-equity-check.org and the data is available in the Supplementary
Information of Robiou du Pont et al. (2017).
The Paris Agreement global goals: What does a fair share for G20 countries look like? 18
2.5 Consistency of equity performance with statements on fairness
All countries recognised the CBDR-RC principle, but countries rarely explained their position with a guiding
principle or a formula applicable to all countries. In their (I)NDCs, Parties were invited to communicate a
description of ‘fairness and ambition’ and a description of ‘how it contributes towards achieving the
objective of the Convention. The statements of the G20 members can be assessed with different
perspectives (Table 3). Some statements invoked notions of fairness that are applicable to all parties and
can constitute a burden sharing approach (‘Fairness principle’ column). Some countries also presented
achievements or targets without relating them to a burden-sharing scale, for example, progress in
ambition, progress compared to business-as-usual (BaU), progress in GDP emissions intensity or the sole
reduction of emissions (‘Additional metrics’ column). Additionally, some (I)NDCs refer to national
circumstances, which are recognised by the Paris Agreement, to justify of the national-specific limits to
reducing emissions domestically (National circumstances’ column). Some countries also stated that their
national emissions represent a small share of the global emissions. These countries may imply that
delivering a fair emissions reduction is either less important than for bigger emitters, which goes against
any fairness principle applicable to all, or costlier due to the low economy of scale. Finally, some countries’
contributions are conditional upon other countries’ ambition in order to avoid relative losses. However,
contributions can also be conditional on technology or finance support, which is inherent to the capability
based principle.
Amongst G20 countries, six did not discuss the fairness of their (I)NDCs, including Turkey who used the
historical responsibility principle only to justify its small contribution to global warming, but not to explain
its current INDC. The EU and its members did not discuss the fairness of their NDC either, but simply “look
forward to discussing with other parties the fairness and ambition of INDCs”. Many Parties implicitly
define the fairness of their contribution as the ambition of their commitment. However, some parties
indicated elements to determine fair mitigation contributions. Amongst G20 countries, ten parties
declared their (I)NDCs fair and ambitious but only six of them mentioned a principle of fairness applicable
to all. Brazil and India discussed the fairness of their NDC under notions of equality, historical responsibility
and capability. The assessment of the Brazilian NDC under the 2 °C goal, which excludes land-use
emissions, is consistent with all the equity allocations, except the capability approach (Robiou du Pont et
al. 2016) (Fig. 7). India’s NDC is consistent with equity approaches representative of concepts of equality
and historical responsibility, but not with the capability approach. Mexico’s NDC is in line with the equal
per capita approach, consistently with its NDC declaration. South Africa calls for a framework applicable
to all and raises concepts of historical responsibility and capability. While the South-African NDC is aligned
with the carbon budget derived by its own national experts (see NDC of South Africa), it is not aligned with
the equal cumulative per capita approach of Figure 7.
Prior to the INDC process, some countries showed support for some concepts of equity at a workshop
under the UNFCCC (2012) or through national communication. Japan supports the consideration for “the
impacts of GHG emissions of each Party on global warming” (Japan 2014, 2). The EU distributes mitigation
efforts across its members states following their historical emissions and capabilities (Commission of the
European Communities 2008, 9; UNFCCC 2012). However, the NDCs of Japan and the EU are not in line
with either the capability or the equal cumulative per capita approaches (Fig. 7). China stressed the
importance of historical responsibility to determine burden sharing efforts (BASIC experts 2011) but its
NDC is not consistent with any of equity approaches including the equal cumulative per capita. Finally, the
G7 INDCs were already found insufficient to equitably meet the ambition of the Elmau agreement signed
by the G7 in June 2015 (Robiou du Pont et al. 2016).
The Paris Agreement global goals: What does a fair share for G20 countries look like? 19
Table 3 | Categorisation of arguments contained in the (I)NDCs’ justifications for fairness and ambition
xiii
. ‘Fairness principles’
relate to equitable burden sharing approaches; ‘Additional metrics’ refer to ambition stated by countries without a relation to a
burden sharing approach (for example: progression in ambition, comparison with developed countries’ contributions, progress
to Business-as-Usual); ‘National circumstance’ refers to elements invoked by Parties to justify of the specific limits to mitigate
domestic emissions; ‘small emitter’ indicates that a Party declared having a small share of global emissions; ‘Conditionality
indicates whether the commitments of a Party are unconditional, conditional or both. The conditionality can be on financial or
technological support, on further agreements, or on economic growth.
Declares
fair and
ambitious
Fairness
principle
No
fairness
justificat
ion for
(I)NDC
Additional
metrics
National
circumstances
Small
emitter
Conditionality
X
Need for development,
food security
X
Both (conditions
on support)
X
Progression,
comparison
National
circumstances,
resource provider, high
abatement costs,
Unconditional
only
‘Very
ambitious’
Equal per
capita,
historical
responsibility,
capability
Progression,
comparison
Need for development,
Unconditional
only
X
BaU,
Progression
Large landmass,
resource provider,
extreme temperatures
X
Not specified
X
Utmost effort
Need for development
Not specified
X
Equal per
capita,
historical
responsibility,
capability
Utmost
ambition
Need for development
Conditional only
(on support)
X
Need for development
Both (conditions
on support)
X
Transparency,
GDP intensity
High mitigation costs,
Not specified
‘Highly
ambitious’
Equal per
capita
Progression
Need for development
X
Both (conditions
on support and
agreement on
carbon pricing)
X
Declining
emissions,
GDP intensity
Not specified
X
BaU
Fossil fuel dependent
economy, vulnerable to
emissions mitigation
Conditional only
(on economic
growth)
X
Calls for
equity
framework,
historical
responsibility,
capability
BaU
Need for development
Both (conditions
on the delivery of
existing support
commitments)
‘To the
extent of
possible’
Fukushima halt to
nuclear,
X
Not specified
Historical
responsibility
X
‘Experiences
constraints’
X
Both (conditions
on support)
X
Not specified
Calls for
discussion on
fairness
X
Progression,
declining
emissions,
GDP intensity
Not specified
xiii
The (I)NDCs are available at: unfccc.int/focus/indc_portal/items/8766.php. The fairness statements extracted from the (I)NDCs by: WRI, CAIT
Climate Data Explorer. 2016. CAIT Paris Contributions Map. Washington, DC: World Resources Institute. (http://cait.wri.org/indcs/).
The Paris Agreement global goals: What does a fair share for G20 countries look like? 20
In 2018, the IPCC will publish a special report to fill the research gap on the differences in climate impact
and mitigation options between 1.5 °C and a 2 °C warming. Recent literature already indicates significant
differences in heat and precipitation extremes, coral reef degradation and in economic impacts.
The Paris Decision target of 40 GtCO2eq in 2030 is a milestone aligned with the 2 °C goal, but insufficient
to align with least-cost scenarios towards 1.5 °C that average at 32.6 GtCO2eq. The Paris Agreement goal
of net-zero emissions in the second half of the century is a requirement for achieving the 1.5 °C goal,
which implies negative emissions soon after mid-century. Following current national commitments results
in mitigation inconsistent with the Paris Agreement goals of 2 °C or 1.5 °C, or with the Paris Decision
indicative target. In concrete terms, achieving emissions reductions consistent with the 1.5 °C goal
requires to lower the global energy demand compared to the 2 °C goal. It also involves greater short-term
deployment of low-carbon technology in the electricity, industrial, transport and building sectors. Overall,
a rapid scale-up of mitigation action is required to meet 2030 emissions consistent with the Paris
Agreement goal of 2 °C, and even more to meet the 1.5 °C goal.
The G20 members played a key towards the Paris Agreement and most already ratified. However, the
ambition of G20 aggregated contributions is insufficient to meet its fair share under any of the five equity
allocations derived from the IPCC fifth assessment report. The G20 can close the 2030 mitigation gap
towards 2 °C and considerably reduce the gap towards 1.5 °C by adopting the average of these five equity
allocations.
Individually, the ambition G20 members differs greatly. While the NDCs of Brazil and Mexico align with
three concepts of equity, the (I)NDCs of China, Russia, Turkey and Saudi Arabia are not consistent with
any. Remarkably, these four Parties also did not invoke any concept of equity when describing the fairness
of their (I)NDCs.
Starting in 2018, the UNFCCC stocktake process provides all Parties with the opportunity to increase and
harmonise the ambition contribution under the CBDR-RC equity principle of the convention.
We gratefully acknowledge the data and support from developers of the PRIMAP emissions module at the
Potsdam Institute for Climate Impact Research (PIK)
xiv
. Deep thanks to Louise Jeffery, John Wiseman,
Cathy Alexander, and Malte Meinshausen for their feedback, and to Anne Houston for the formatting
arrangements.
xiv
www.pik-potsdam.de/research/climate-impacts-and-vulnerabilities/research/rd2-flagship-projects/gia/primap
The Paris Agreement global goals: What does a fair share for G20 countries look like? 21
Averchenkova, Alina, Nicholas Stern, and Dimitri Zenghelis. 2014. “Taming the Beasts of ‘ Burden-Sharing
’: An Analysis of Equitable Mitigation Actions and Approaches to 2030 Mitigation Pledges.” Centre
for Climate Change Economics and Policy - Grantham Research Institute on Climate Change and
the Environment. London. http://www.lse.ac.uk/GranthamInstitute/publication/taming-the-
beasts-of-burden-sharing-an-analysis-of-equitable-mitigation-actions-and-approaches-to-2030-
mitigation-pledges/.
Baer, Paul, Glenn Fieldman, Tom Athanasiou, and Sivan Kartha. 2008. “Greenhouse Development Rights:
Towards an Equitable Framework for Global Climate Policy.” Cambridge Review of International
Affairs 21 (August 2014): 64969. doi:10.1080/09557570802453050.
BASIC experts. 2011. “Equitable Access to Sustainable Development: Contribution to the Body of Scientific
Knowledge.” Edited by Harald Winkler, T. Jayaraman, Jiahua Pan, Yongsheng Santhiago de
Oliveira, Adriano Zhang, Girish Sant, Jose Domingos Gonzalez Miguez, Thapelo Letete, Marquard
Andrew, and Stefan Raubenheimer. BASIC Expert Group: Beijing, Brasilia, Cape Town and
Mumbai. Beijing, Brasilia, Cape Town and Mumbai.
Burke, Marshall, Solomon M Hsiang, and Edward Miguel. 2015. “Global Non-Linear Effect of Temperature
on Economic Production.” Nature 527 (November): 23539. doi:10.1038/nature15725.
Caney, Simon. 2009. “Justice and the Distribution of Greenhouse Gas Emissions.” Journal of Global Ethics
5 (2): 12546. doi:10.1080/17449620903110300.
Commission of the European Communities. 2008. “Impact Assessment: Document Accompanying the
Package of Implementation Measures for the EU’s Objectives on Climate Change and Renewable
Energy for 2020 Proposals.” Brussels.
http://ec.europa.eu/clima/policies/strategies/2020/docs/sec_2008_85_ia_en.pdf.
Edenhofer, O., R. Pichs-Madruga, Y. Sokona, E. Farahani, S. Kadner, K. Seyboth, A. Adler, et al. 2014.
“Chapter 6 Assessing Transformation Pathways IPCC WGIII AR5.”
http://www.ipcc.ch/pdf/assessment-report/ar5/wg3/ipcc_wg3_ar5_chapter6.pdf.
Fischer, E M, and R Knutti. 2015. “Anthropogenic Contribution to Global Occurrence of Heavy-
Precipitation and High-Temperature Extremes.” Nature Climate Change 5 (June): 56064.
doi:10.1038/NCLIMATE2617.
Frieler, K, M. Meinshausen, A. Golly, M. Mengel, K. Lebek, S. D. Donner, and O. Hoegh-Guldberg. 2012.
“Limiting Global Warming to 2 Degree C Is Unlikely to Save Most Coral Reefs.” Nature Climate
Change 3 (2). Nature Publishing Group: 16570. doi:10.1038/nclimate1674.
Frieler, Katja, Richard Betts, Eleanor Burke, Philippe Ciais, Sebastien Denvil, Kristie Ebi, Tyler Eddy, et al.
2016. “Assessing the Impacts of 1.5 ° C Global Warming Simulation Protocol of the Inter-Sectoral
Impact Model Intercomparison Project ( ISIMIP2b ).” Geoscientific Model Development Discussion,
no. October: 159. doi:10.5194/gmd-2016-229.
Gütschow, Johannes, M Louise Jeffery, Robert Gieseke, Ronja Gebel, David Stevens, Mario Krapp, and
Marcia Rocha. 2016. “The PRIMAP-Hist National Historical Emissions Time Series.” Earth System
Science Data 8: 571603. doi:10.5194/essd-8-571-2016.
IPCC. 2014. “Summary for Policymakers - Draft.” In Climate Change 2014, Mitigation of Climate Change.
Contribution of Working Group III to the Fifth Assessment Report of the Intergovernmental Panel
on Climate Change, edited by T. Zwickel and J.C. Minx Edenhofer O., R. Pichs-Madruga, Y. Sokona,
The Paris Agreement global goals: What does a fair share for G20 countries look like? 22
E. Farahani, S. Kadner, K. Seyboth, A. Adler, I. Baum, S. Brunner, P. Eickemeier, B. Kriemann, J.
Savolainen, S. Schlömer, C. von Stechow, 133. Cambridge, United Kingdom and New York, NY,
USA: Cambridge University Press.
http://www.climatechange2013.org/images/report/WG1AR5_SPM_FINAL.pdf.
Japan. 2014. “Submission by Japan - Information, Views and Proposals on Matters Related to the Work of
Ad Hoc Working Group on the Durban Platform for Enhanced Action (ADP) Workstream 1.” Bonn.
http://unfccc.int/files/bodies/awg/application/pdf/[japan_submission]_adp.pdf.
Kemp-Benedict, Eric. 2010. “Calculations for the Greenhouse Development Rights Calculator.” Stockholm,
Sweden.
Levermann, Anders, Peter U Clark, Ben Marzeion, Glenn A Milne, David Pollard, and Valentina Radic. 2013.
“The Multimillennial Sea-Level Commitment of Global Warming.” PNAS 110 (34).
doi:10.1073/pnas.1219414110.
Meinshausen, M., S. C. B. Raper, and T. M. L. Wigley. 2011. “Emulating Coupled Atmosphere-Ocean and
Carbon Cycle Models with a Simpler Model, MAGICC6 Part 1: Model Description and
Calibration.” Atmospheric Chemistry and Physics 11 (4): 141756. doi:10.5194/acp-11-1417-2011.
Meinshausen, Malte, and Ryan Alexander. 2015. “INDC Factsheets.” Australian-German Climate and
Energy College. http://climatecollege.unimelb.edu.au/indc-factsheets/.
Meinshausen, Malte, Louise Jeffery, Johannes Guetschow, Yann Robiou du Pont, Joeri Rogelj, Michiel
Schaeffer, Niklas Höhne, Michel den Elzen, Sebastian Oberthür, and Nicolai Meinshausen. 2015.
“National Post-2020 Greenhouse Gas Targets and Diversity-Aware Leadership.” Nature Climate
Change 5 (December): 10981106. doi:10.1038/nclimate2826.
Nabel, Julia E M S, Joeri Rogelj, Claudine M. Chen, Kathleen Markmann, David J H Gutzmann, and Malte
Meinshausen. 2011. “Decision Support for International Climate Policy - The PRIMAP Emission
Module.” Environmental Modelling and Software 26 (12): 141933.
doi:10.1016/j.envsoft.2011.08.004.
Nauels, Alexander, Malte Meinshausen, Matthias Mengel, Katja Lorbacher, M Tom, and L Wigley. 2016.
“Synthesizing Long-Term Sea Level Rise Projections - the MAGICC Sea Level Model.” Geoscientific
Model Development Discussion, no. October: 140. doi:10.5194/gmd-2016-233.
Peters, Glen P, Robbie M Andrew, Susan Solomon, and Pierre Friedlingstein. 2015. “Measuring a Fair and
Ambitious Climate Agreement Using Cumulative Emissions.” Environmental Research Letters 10
(10). IOP Publishing: 105004. doi:10.1088/1748-9326/10/10/105004.
Raupach, Michael R., Steven J. Davis, Glen P. Peters, Robbie M. Andrew, Josep G. Canadell, Philippe Ciais,
Pierre Friedlingstein, Frank Jotzo, Detlef P. van Vuuren, and Corinne Le Quéré. 2014. “Sharing a
Quota on Cumulative Carbon Emissions.” Nature Climate Change 4 (September): 873879.
doi:10.1038/nclimate2384.
Robiou du Pont, Yann, M Louise Jeffery, Johannes Gütschow, Peter Christoff, and Malte Meinshausen.
2016. “National Contributions for Decarbonizing the World Economy in Line with the G7
Agreement.” Environmental Research Letters 11 (5). IOP Publishing: 54005. doi:10.1088/1748-
9326/11/5/054005.
Robiou du Pont, Yann, M Louise Jeffery, Johannes Gutschow, Joeri Rogelj, Peter Christoff, and Malte
Meinshausen. 2017. “Equitable Mitigation to Achieve the Paris Agreement Goals.” JOUR. Nature
Clim. Change 7 (1). Nature Publishing Group: 3843. http://dx.doi.org/10.1038/nclimate3186.
The Paris Agreement global goals: What does a fair share for G20 countries look like? 23
Robiou du Pont, Yann, M Louise Jeffery, Johannes Gütschow, Joeri Rogelj, Peter Christoff, and Malte
Meinshausen. 2017. “Equitable Mitigation to Achieve the Paris Agreement Goals.” Nature Climate
Change 7 (January): 3843. doi:10.1038/NCLIMATE3186.
Rogelj, Joeri, Michel Den Elzen, Niklas Höhne, Taryn Fransen, Hanna Fekete, Harald Winkler, Roberto
Schaeffer, and Fu Sha. 2016. “Paris Agreement Climate Proposals Need a Boost to Keep Warming
Well below 2 ° C.” Nature 534 (June): 631639. doi:10.1038/nature18307.
Rogelj, Joeri, and Reto Knutti. 2016. “Geosciences after Paris.” Nature Publishing Group, 13.
doi:10.1038/ngeo2668.
Rogelj, Joeri, Gunnar Luderer, Robert C. Pietzcker, Elmar Kriegler, Michiel Schaeffer, Volker Krey, and
Keywan Riahi. 2015. “Energy System Transformations for Limiting End-of-Century Warming to
below 1.5 °C.” Nature Climate Change 5 (6). Nature Publishing Group: 51927.
doi:10.1038/nclimate2572.
Rogelj, Joeri, David L McCollum, Andy Reisinger, Malte Meinshausen, and Keywan Riahi. 2013.
“Probabilistic Cost Estimates for Climate Change Mitigation.” Nature 493 (7430): 7983.
doi:10.1038/nature11787.
Rogelj, Joeri, Shilpa Rao, David L Mccollum, Shonali Pachauri, Zbigniew Klimont, Volker Krey, and Keywan
Riahi. 2014. “Air-Pollution Emission Ranges Consistent with the Representative Concentration
Pathways.” Nature Climate Change 4 (May): 44650. doi:10.1038/NCLIMATE2178.
Schellnhuber, Hans Joachim, Stefan Rahmstorf, and Ricarda Winkelmann. 2016. “Why the Right Climate
Target Was Agreed in Paris.” Nature Climate Change 6 (July): 64953. doi:10.1038/nclimate3013.
Schleussner, Carl-Friedrich, T. K. Lissner, E. M. Fischer, J. Wohland, M. Perrette, A. Golly, J. Rogelj, et al.
2016. “Differential Climate Impacts for Policy-Relevant Limits to Global Warming: The Case of 1.5
°C and 2 °C.” Earth System Dynamics Discussions 6 (2): 24472505. doi:10.5194/esdd-6-2447-
2015.
Schleussner, Carl-Friedrich, Joeri Rogelj, Michiel Schaeffer, Tabea Lissner, Rachel Licker, Erich M Fischer,
Reto Knutti, Anders Levermann, Katja Frieler, and William Hare. 2016. “Science and Policy
Characteristics of the Paris Agreement Temperature Goal.” Nature Climate Change, no. July.
Nature Publishing Group. doi:10.1038/nclimate3096.
UNEP. 2015. “The Emission Gap Report 2015. A UNEP Synthesis Report.” Nairobi.
http://www.unep.org/publications/ebooks/emissionsgapreport/index.asp.
UNFCCC. 1992. “United Nations Framework Convention on Climate Change. Report No.
FCCC/INFORMAL/84.” Report No. FCCC/INFORMAL/84. Rio. doi:10.1111/j.1467-
9388.1992.tb00046.x.
———. 2012. “Report on the Workshop on Equitable Access to Sustainable Development.” Bonn.
http://unfccc.int/resource/docs/2012/awglca15/eng/inf03r01.pdf.
———. 2015a. “Adoption of the Paris Agreement. Report No. FCCC/CP/2015/L.9/Rev.1.” Vol. 21932. Paris,
France. http://unfccc.int/resource/docs/2015/cop21/eng/l09r01.pdf.
———. 2015b. “Paris Agreement.” Paris, France.
https://unfccc.int/files/essential_background/convention/application/pdf/english_paris_agree
ment.pdf.
———. 2015c. “Synthesis Report on the Aggregate Effect of the Intended Nationally Determined
Contributions.” Vol. FCCC/CP.
The Paris Agreement global goals: What does a fair share for G20 countries look like? 24
World Bank. 2014. “World Development Indicators.” Washington DC.
http://data.worldbank.org/sites/default/files/wdi-2014-book.pdf.
... The six categories have been used to highlight all plausible equity principles or fairness arguments to share efforts in the international community [10,11]. Hence, allocations resulting from these effort-sharing categories could facilitate in providing ranges and boundaries of countries' fair contributions in the future [12,13]. Current climate negotiations have focused on countries' mitigation targets in the INDCs. ...
... In the NDC, China has not yet implemented explicit mitigation targets addressing non-CO 2 emissions. Robiou Du Pont et al. [13,63] showed that China's projected greenhouse gas emissions (including both CO 2 and non-CO 2 ), based on annual comparisons in 2030, might not align with any equity principle (it is noted that Robiou Du Pont et al. considered only one effort-sharing scheme per IPCC category, and didn't cover the categories of responsibility and cost-effectiveness). However, if we focus exclusively on CO 2 (what is covered in the NDC), our findings here (based on a more comprehensive effort-sharing framework accounting for more schemes per IPCC category) have demonstrated that, China's CO 2 mitigation targets could possibly meet upper ends of fair ranges of carbon allowances (especially when we consider cumulative emissions), which is largely in agreement with the assessment of CAT (CAT considered greenhouse gas emissions and made annual comparisons in the year 2030). ...
Article
Full-text available
Nationally Determined Contributions (NDCs) are a core component for post-2020 global climate agreements to achieve the 2 °C goal in addressing climate change. In the NDC, China has declared to lower carbon intensity by 60-65% from the 2005 level by 2030 and achieve the peak of CO2 emissions around 2030. In the context of the 2 °C goal, this study assesses China's CO2 mitigation targets in the NDC using fair ranges of emissions allowances as calculated from an effort-sharing framework based on six equity principles (and cost-effectiveness). Results show that understanding the fairness of China's NDC would rely heavily on selected equity principles. If the 65% target is implemented, China's NDC would position within full ranges of emissions allowances and align with responsibility-capacity-need based on comparisons in 2030, and with responsibility-capacity-need and equal cumulative per capita emissions based on comparisons during 2011-2030. Implications of the NDC on China's long-term CO2 mitigation targets beyond 2030 are also explored, which indicate that China's energy system would need to realize carbon neutrality by 2070s at the latest in the scenarios in this study.
... Finally, recent literature (e.g. Aldy et al., 2017;Brown et al., 2018;Höhne et al., 2017;Holz et al., 2018;Pan et al., 2018;Robiou Du Pont et al., 2017;Robiou du Pont, 2017;Zimm & Nakicenovic, 2019) has also started to scope out comparisons of a few or groups of countries' NDC targets to assess fairness. While equity and fairness remain important topics in global climate negotiations and domestic implementation (Klinsky et al., 2017;Moellendorf, 2012), policy and technological innovation and leadership around the world are important global drivers of climate ambition and socio-economic transformational changes (Biedenkopf et al., 2017;Schwerhoff, 2016;Victor et al., 2019). ...
... These five categories include notions of capability to pay (CAP approach), equality with the dynamic Equal Per Capita (EPC) approach, responsibility-capability-need with the Greenhouse Development Rights (GDR), historical responsibility with the Equal Cumulative Per Capita (CPC) and national circumstances regarding current emissions levels with the grandfathering approach (also named Constant Emissions Ratio or CER). The grandfathering approach, a status-quo approach that allocates equal emissions mitigation rates to all countries, is considered unfair 12,41 and not openly supported by any country but implicitly matches many developed countries' targets 8 , which they often declare as fair 42 . Under the complete bottom-up modelling setup (Supplementary Table 1), each country follows the approach, from the complete set of five effort-sharing approaches, that yields the greatest cumulative emissions over the 2010-2100 period (Fig. 1a, Supplementary Fig. 1). ...
Article
Full-text available
Under the bottom-up architecture of the Paris Agreement, countries pledge Nationally Determined Contributions (NDCs). Current NDCs individually align, at best, with divergent concepts of equity and are collectively inconsistent with the Paris Agreement. We show that the global 2030-emissions of NDCs match the sum of each country adopting the least-stringent of five effort-sharing allocations of a well-below 2 °C-scenario. Extending such a self-interested bottom-up aggregation of equity might lead to a median 2100-warming of 2.3 °C. Tightening the warming goal of each country’s effort-sharing approach to aspirational levels of 1.1 °C and 1.3 °C could achieve the 1.5 °C and well-below 2 °C-thresholds, respectively. This new hybrid allocation reconciles the bottom-up nature of the Paris Agreement with its top-down warming thresholds and provides a temperature metric to assess NDCs. When taken as benchmark by other countries, the NDCs of India, the EU, the USA and China lead to 2.6 °C, 3.2 °C, 4 °C and over 5.1 °C warmings, respectively.
Thesis
Full-text available
With the Paris Agreement, the international community has agreed to limit global warming to well below 2 °C and to pursue efforts to stay below 1.5 °C (UNFCCC 2015a) to avoid dangerous climate impacts. Staying within these boundaries requires important emissions mitigation efforts from all countries (Rogelj et al 2015). Equitable distribution across countries of mitigation efforts, or equivalently of emissions rights, consistent with global mitigation objectives is a contentious issue that involves divergent interpretations of distributive justice (Winkler and Rajamani 2014a). The latest Intergovernmental Panel on Climate Change (IPCC) report categorises equity approaches from the scientific literature in five groups (Clarke et al 2014). At climate negotiations, most countries tend to support the approach that requires the least efforts on their behalf (Fleurbaey et al 2014, Lange et al 2010). With the absence of consensus on an effort-sharing approach, current negotiations under the United Nations Framework Convention on Climate Change (UNFCCC) follow a self-interested, or ‘bottom-up’, approach to target setting (Andresen 2015, Bodansky 2016) where each country decides its own effort following its understanding of fairness. As a result, the sum of all parties’ announced contributions is not consistent with limiting global warming to 2 °C, let alone 1.5 °C (Rogelj et al 2016a). Under the Paris Agreement, countries committed to increase the ambition of their post-Kyoto climate pledges through a ratcheting-up process that begins in 2023. With the disagreement on effort-sharing approaches, the international community relies on diverging metrics to evaluate the adequacy of national pledges with the global warming thresholds. Since the beginning of climate negotiations under the United Nations, a rich literature has modelled allocations of emissions rights to countries using various effort-sharing approaches with uncoordinated parameterisation. At the start of this PhD work, no study modelled the effort-sharing categories presented in the last IPCC report under a common parameterisation. Additionally, the literature on the combination of effort-sharing approaches remained thin and consisted of averaging the emissions allocations of multiple effort-sharing approaches. This PhD thesis addresses these gaps with the modelling of a new emissions allocation framework, the ‘PRIMAP-Equity’ framework, and with the suggestion of a new combination of effort-sharing approaches. Firstly, this thesis quantifies allocations of emissions rights to countries in a manner that reflects the existing literature on distributive justice. An emissions allocation framework is developed to derive national emissions allocations that reflect the five equity categories of the fifth IPCC report. This modelling framework is applied to derive emissions allocations, under each of the five equity categories, consistent with the emissions mitigation goals of the G7 Elmau agreement signed in June 2015. The allocation framework is then used to derive national emissions trajectories aligned with the recent Paris Agreement goals of both well below 2 °C and 1.5 °C, consistently with the five equity categories. This work represents the first quantification of equitable national trajectories to achieve 1.5 °C goal and informs scientists and government experts in the preparation of the IPCC Special Report on 1.5 °C (IPCC 2017). The Nationally Determined Contributions (NDCs), countries’ national pledges, of 171 Parties are then evaluated in order to determine which, if any, categories of equity they are consistent with. As well, the thesis highlights the consistency of G20 countries’ pledges with equity allocations. This is discussed in the context of the statement on fairness contained in each pledge. This PhD thesis then addresses the apparent incompatibility between the global warming thresholds and countries’ self-interested visions of effort-sharing by suggesting a new quantitative approach. Doing so, this PhD thesis provides a new metric, inclusive of all international positions, to assess the ambition of the NDCs under the Paris Agreement. This new ‘hybrid’ allocation method reconciles the ‘bottom-up’ approach of equity with the ‘top-down’ climate threshold that they commonly agreed. Under this ‘hybrid’ approach, each country follows the least stringent effort-sharing approach – out of the five that reflect the equity categories presented in the last IPCC report – to achieve the Paris Agreement. The aggregation of current national pledges is found to align with such a ‘bottom-up’ combination of approaches and lead to a warming of up to 2.3 °C in 2100 (with a 50% chance). Conversely, an enhanced ‘bottom-up’ approach – ‘hybrid’ – of global emissions scenarios leading to 1.1 °C and 1.3 °C warmings results in the achievement of the Paris Agreement mitigation goals of 1.5 °C and well below 2 °C, respectively. Ultimately, this study quantifies a compromise where each country can choose an equity approach to determine its effort, but does directly use that approach to assess other countries’ pledges. Finally, the application of this ‘hybrid’ approach provides a temperature assessment for all countries’ climate pledges, indicating the consistency of countries’ ambition in light of the global temperature goals. The NDCs of India, the EU, the USA and China are in line with global ‘bottom-up’ situations leading to warmings of 2.6 °C, 3.2 °C, 4 °C and over 5.1 °C, respectively. The results of this thesis can inform public opinions and decision makers through the ratcheting-up process on what constitutes fair and ambitious pledges to achieve the Paris Agreement following a range or combination of equity approaches. Additionally, the assessments of the adequacy of countries’ pledges with international agreements can inform courts when ruling ‘climate cases’ where governments are sued for their lack of ambition in mitigating emissions (Sabin Center for Climate Change Law 2018).
Article
Full-text available
To assess the history of greenhouse gas emissions and individual countries' contributions to emissions and climate change, detailed historical data are needed. We combine several published datasets to create a comprehensive set of emissions pathways for each country and Kyoto gas, covering the years 1850 to 2014 with yearly values, for all UNFCCC member states and most non-UNFCCC territories. The sectoral resolution is that of the main IPCC 1996 categories. Additional time series of CO2 are available for energy and industry subsectors. Country-resolved data are combined from different sources and supplemented using year-to-year growth rates from regionally resolved sources and numerical extrapolations to complete the dataset. Regional deforestation emissions are downscaled to country level using estimates of the deforested area obtained from potential vegetation and simulations of agricultural land. In this paper, we discuss the data sources and methods used and present the resulting dataset, including its limitations and uncertainties. The dataset is available from doi:10.5880/PIK.2016.003 and can be viewed on the website accompanying this paper (http://www.pik-potsdam.de/primap-live/primap-hist/).
Article
Full-text available
In Paris, France, December 2015, the Conference of the Parties (COP) to the United Nations Framework Convention on Climate Change (UNFCCC) invited the Intergovernmental Panel on Climate Change (IPCC) to provide a "special report in 2018 on the impacts of global warming of 1.5 °C above pre-industrial levels and related global greenhouse gas emission pathways". In Nairobi, Kenya, April 2016, the IPCC panel accepted the invitation. Here we describe the response devised within the Inter-Sectoral Impact Model Intercomparison Project (ISIMIP) to provide tailored, cross-sectorally consistent impacts projections. The simulation protocol is designed to allow for (1) separation of the impacts of historical warming starting from pre-industrial conditions from other human drivers such as historical land-use changes (based on pre-industrial and historical impact model simulations); (2) quantification of the effects of additional warming up to 1.5 °C, including a potential overshoot and long-term effects up to 2299, compared to a no-mitigation scenario (based on the low-emissions Representative Concentration Pathway RCP2.6 and a no-mitigation pathway RCP6.0) with socio-economic conditions fixed at 2005 levels; and (3) assessment of the climate effects based on the same climate scenarios but accounting for simultaneous changes in socio-economic conditions following the middle-of-the-road Shared Socioeconomic Pathway (SSP2, Fricko et al., 2016) and differential bio-energy requirements associated with the transformation of the energy system to comply with RCP2.6 compared to RCP6.0. With the aim of providing the scientific basis for an aggregation of impacts across sectors and analysis of cross-sectoral interactions that may dampen or amplify sectoral impacts, the protocol is designed to facilitate consistent impacts projections from a range of impact models across different sectors (global and regional hydrology, global crops, global vegetation, regional forests, global and regional marine ecosystems and fisheries, global and regional coastal infrastructure, energy supply and demand, health, and tropical cyclones).
Article
Full-text available
Sea level rise is one of the major impacts of global warming; it will threaten coastal populations, infrastructure, and ecosystems around the globe in coming centuries. Well-constrained sea level projections are needed to estimate future losses from Sea Level Rise (SLR) and benefits of climate protection and adaptation. Process-based models that are designed to resolve the underlying physics of individual sea level drivers form the basis for state-of-the-art sea level projections. However, associated computational costs allow for only a small number of simulations based on selected scenarios that often vary for different sea level components. This approach does not sufficiently support sea level impact science and climate policy advice, which require a sea level projection methodology that is flexible with regard to the climate scenario yet comprehensive and bound to the physical constraints provided by process-based models. To fill this gap, we present a sea level model that emulates global mean long-term process-based model projections for all major sea level components. Thermal expansion estimates are calculated with the hemispheric upwelling-diffusion ocean component of the simple carbon cycle-climate model MAGICC, which has been updated and calibrated against CMIP5 ocean temperature profiles and thermal expansion data. Global glacier contributions are estimated based on a parameterization constrained by transient and equilibrium process-based projections. Sea level contribution estimates for Greenland and Antarctic ice sheets are derived from surface mass balance and solid ice discharge parameterizations reproducing current output from ice-sheet models. The land water storage component replicates the latest hydrological modeling results. For 2100, we project 0.38 m to 0.59 m (66 % range) total SLR based on the RCP2.6 scenario, 0.48 m to 0.68 m for RCP4.5, 0.48 m to 0.72 m for RCP6.0, and 0.67 m to 0.97 m for RCP8.5. These projections lie within the range of the latest IPCC SLR estimates. SLR projections for 2300 yield median responses of 0.97 m for RCP2.6, 1.66 m for RCP4.5, 2.32 m for RCP6.0, and 5.12 m for RCP8.5. The MAGICC sea level model provides a powerful and efficient platform for probabilistic uncertainty analyses of long-term SLR projections. It can be used as a tool to directly investigate the SLR implications of different mitigation pathways and may also serve as input for regional SLR assessments via component-wise sea level pattern scaling.
Article
Full-text available
The Paris Agreement sets a long-term temperature goal of holding the global average temperature increase to well below 2 °C, and pursuing efforts to limit this to 1.5 °C above pre-industrial levels. Here, we present an overview of science and policy aspects related to this goal and analyse the implications for mitigation pathways. We show examples of discernible differences in impacts between 1.5 °C and 2 °C warming. At the same time, most available low emission scenarios at least temporarily exceed the 1.5 °C limit before 2100. The legacy of temperature overshoots and the feasibility of limiting warming to 1.5 °C, or below, thus become central elements of a post-Paris science agenda. The near-term mitigation targets set by countries for the 2020-2030 period are insufficient to secure the achievement of the temperature goal. An increase in mitigation ambition for this period will determine the Agreement's effectiveness in achieving its temperature goal.
Article
Full-text available
To assess the history of greenhouse gas emissions and individual countries' contributions to emissions and climate change, detailed historical data is needed. We combine several published datasets to create a comprehensive set of emission pathways of each country and Kyoto gas covering the years 1850 to 2014 for all UNFCCC member states as well as most non-UNFCCC territories. The sectoral resolution is that of the main IPCC 1996 categories. Additional subsectors are available for time series of CO2 from energy and industry. Country resolved data is combined from different sources and supplemented using growth rates from region resolved sources and numerical extrapolations to complete the dataset. Regional deforestation emissions are downscaled to country level using estimates of the deforested area obtained from potential vegetation and simulations of agricultural land. In this paper, we discuss the data sources and methods used and present the resulting dataset including its limitations and uncertainties. The dataset is available from http://doi.org/10.5880/PIK.2016.003 and can be viewed on the website accompanying this paper (www.pik-potsdam.de/primap-live/primap-hist/).
Article
Full-text available
In June 2015, the G7 agreed to two global mitigation goals: 'a decarbonization of the global economy over the course of this century' and 'the upper end of the latest Intergovernmental Panel on Climate Change (IPCC) recommendation of 40%–70% reductions by 2050 compared to 2010'. These IPCC recommendations aim to preserve a likely (>66%) chance of limiting global warming to 2 °C but are not necessarily consistent with the stronger ambition of the subsequent Paris Agreement of 'holding the increase in the global average temperature to well below 2 °C above pre-industrial levels and to pursue efforts to limit the temperature increase to 1.5 °C above pre-industrial levels'. The G7 did not specify global or national emissions scenarios consistent with its own agreement. Here we identify global cost-optimal emissions scenarios from Integrated Assessment Models that match the G7 agreement. These scenarios have global 2030 emissions targets of 11%–43% below 2010, global net negative CO2 emissions starting between 2056 and 2080, and some exhibit net negative greenhouse gas emissions from 2080 onwards. We allocate emissions from these global scenarios to countries according to five equity approaches representative of the five equity categories presented in the Fifth Assessment Report of the IPCC (IPCCAR5): 'capability', 'equality', 'responsibility-capability-need', 'equal cumulative per capita' and 'staged approaches'. Our results show that G7 members' Intended Nationally Determined Contribution (INDCs) mitigation targets are in line with a grandfathering approach but lack ambition to meet various visions of climate justice. The INDCs of China and Russia fall short of meeting the requirements of any allocation approach. Depending on how their INDCs are evaluated, the INDCs of India and Brazil can match some equity approaches evaluated in this study.
Article
Benchmarks to guide countries in ratcheting-up ambition, climate finance, and support in an equitable manner are critical but not yet determined in the context of the Paris Agreement. We identify global cost-optimal mitigation scenarios consistent with the Paris Agreement goals and allocate their emissions dynamically to countries according to five equity approaches. At the national level, China's Nationally Determined Contribution (NDC) is weaker than any of the five equity approaches, India's NDC is aligned with two, and the EU's and the USA's with three. Most developing countries' conditional (Intended) NDCs (INDCs) are more ambitious than the average of the five equity approaches under the 2 °C goal. If the G8 and China adopt the average of the five approaches, the gap between conditional INDCs and 2 °C-consistent pathways could be closed. For an equitable, cost-optimal achievement of the 1.5 °C target, emissions in 2030 are 21% lower (relative to 2010) than for 2 °C for the G8 and China combined, and 39% lower for remaining countries. Equitably limiting warming to 1.5 °C rather than 2 °C requires that individual countries achieve mitigation milestones, such as peaking or reaching net-zero emissions, around a decade earlier. © 2017 Macmillan Publishers Limited, part of Springer Nature. All rights reserved.
Article
The Paris climate agreement aims at holding global warming to well below 2 degrees Celsius and to “pursue efforts” to limit it to 1.5 degrees Celsius. To accomplish this, countries have submitted Intended Nationally Determined Contributions (INDCs) outlining their post-2020 climate action. Here we assess the effect of current INDCs on reducing aggregate greenhouse gas emissions, its implications for achieving the temperature objective of the Paris climate agreement, and potential options for overachievement. The INDCs collectively lower greenhouse gas emissions compared to where current policies stand, but still imply a median warming of 2.6–3.1 degrees Celsius by 2100. More can be achieved, because the agreement stipulates that targets for reducing greenhouse gas emissions are strengthened over time, both in ambition and scope. Substantial enhancement or over-delivery on current INDCs by additional national, sub-national and non-state actions is required to maintain a reasonable chance of meetin
Article
The Paris Agreement duly reflects the latest scientific understanding of systemic global warming risks. Limiting the anthropogenic temperature anomaly to 1.5–2 °C is possible, yet requires transformational change across the board of modernity.
Article
The adoption of the Paris Agreement is a historic milestone for the global response to the threat of climate change. Scientists are now being challenged to investigate a 1.5 °C world — which will require an accelerated effort from the geoscience community.