Climate Stabilization Targets Research Articles

The choice of land-based climate change mitigation measures influences future global biodiversity loss

Climate mitigation is reported to benefit biodiversity globally. However, the impacts of mitigation measures based on large-scale land-use modifications can be concentrated in the regions where they are introduced, resulting in regional mismatches between mitigation efforts and biodiversity benefits. Here, we evaluated the impacts of large-scale deployment of bioenergy with carbon capture and storage and afforestation to attain the climate stabilization target stated by the Paris Agreement on global and regional biodiversity by using an integrated model framework. Our results highlight that climate mitigation efforts can benefit global biodiversity regardless of large-scale implementation of land-based mitigation measures. However, the negative impacts of mitigation measures on biodiversity are concentrated in regions with a higher contribution to land-use change and carbon sequestration. The results imply the need to consider the unequal regional distribution of benefits from climate mitigation, as well as mitigation options that avoid regional biodiversity loss by minimizing land-use change.

Radiative forcing climate footprints in the agricultural sector: Comparison of models from the IPCC 5th and 6th Assessment Reports

To achieve the goal in the Paris Agreement of limiting mean global temperature rise to 1.5 ​°C, total anthropogenic radiative forcing (RF) should be reduced from current 2.7 to around 1.9 ​W ​m−2. A newly developed RF-based climate footprint (RFCF) indicator, which quantifies the additional contribution to RF associated with current and historical emissions, can support transparent alignment with climate stabilization targets by assessing the profile of RF over time. Nevertheless, RFCF applications to date have been based on parameters and equations from IPCC 5th Assessment Report (AR). Considering the latest updates in the IPCC 6th AR, we applied the RFCF approach for the first time in a case study involving the Australian agricultural sector. We compared the RF, RFCF and annual changes in RFCF of CH4, N2O and CO2 using both models. All the results of RF as well as RFCF calculated using the latest model were slightly lower than those obtained using the former model. The agricultural sector's contribution to RF had plateaued in recent years and is projected to reach the point of net zero increase in 2022 (IPCC 6th AR model) or 2023 (IPCC 5th AR model). Considering the latest updates in emission lifetime, radiative efficiency and indirect effects based on the background concentration (1750–2019), the assessments based on IPCC 6th AR model provide more reliable results. However, a dynamic model is required to reflect the additional RF for the pulse emission based on the relevant climate background in the same year. The RF-based footprint approach can support national greenhouse gas emission reduction policy targets, especially for sectors with substantial biogenic methane emissions.

Kinetic Study of Heterogeneous Photocatalytic CO2 Reduction: Development of a General Formula for Relations between Activity and Reaction Conditions

Recently, the development of technologies for CO2 emission reduction has been extensively investigated to achieve the global 2 °C climate stabilization target. This study demonstrates that the photocatalytic activity and selectivity toward carbon monoxide (CO) evolution for the selective photocatalytic conversion of CO2 to CO, using H2O as an electron donor, are significantly dependent on the reaction conditions, such as additive concentration, CO2 partial pressure, and reaction temperature. The systematic experiments performed in this study revealed that the CO formation rate was proportional to the increase in the CO2 partial pressure and inversely proportional to the proton (H+) concentration in the reaction solution. Based on these results, a quantitative expression for the formation rate of CO with CO2 partial pressure and pH as variables was developed using kinetics, considering the equilibria of surface hydroxyl groups. This study confirmed that the derived mathematical expressions matched well with the experimental results of three different photocatalysts, whose activities and selectivities were completely different. Moreover, based on these expressions, a theoretical method is proposed to determine the kinetic constant and activation energy for the reduction of adsorbed CO2 molecules. The developed mathematical expression for photocatalytic CO2 conversation in water contributes to the development of CO2 recycling technologies.

Innovation in low-energy demand and its implications for policy

AbstractScenarios featuring low-energy demand (LED) have the potential to meet climate stabilization targets while also pursuing inclusive well-being and multiple Sustainable Development Goals. Recent papers have assembled detailed bottom-up estimates to inform integrated assessment modeling and show that LED outcomes are feasible and have beneficial effects across multiple goals. But realizing the full potential in LED depends on innovation—i.e. improvement in LED technology and widespread adoption of both LED technology and behavior—as well as policies supporting innovation. We review the literature to better understand the role of technological innovation in enabling LED scenarios and how policy interventions can stimulate those innovations. We structure our review using a policy analysis framework that includes specifying multiple LED policy goals, describing the distinct characteristics of LED technology to understand policy needs. The distinct characteristics of LED innovation include multiple attributes and new services; many heterogeneous adopters; small granular scale, many iterations; local system integration; and rebound effects, among others. We also consider five important drivers of change in LED innovation: higher living standards and preferences for clean environments, urbanization, digitalization, demand for novel services and the emergence of prosumers. The analysis in this review of the literature leads to nine LED policy design guidelines.

Substitution of beef with pea protein reduces the environmental footprint of meat balls whilst supporting health and climate stabilisation goals

Recent environmental footprint comparisons between meat and plant-based meat analogues do not consider nutritional density holistically, nor the high carbon opportunity costs (COC) of land requirements, which are critical in terms of climate stabilisation targets. We performed an attributional life cycle assessment (LCA) of a 100 g serving of cooked protein balls (PPBs) made from peas (Pisum sativum), and Swedish-style beef meatballs (MBs) made from Irish or Brazilian beef. Per serving, PPB production and consumption was associated with lower environmental burdens across all 16 categories assessed. Global warming, acidification, and land use burdens of PPBs were at least 85%, 81%, and 89% smaller, respectively, than MBs. The scale of environmental advantage was sensitive to the allocation method, with biophysical allocation across cattle co-products decreasing MB burdens by at least 35%, 38%, and 46% in the acidification, climate change, and land use categories, respectively. Furthermore, PPBs have a higher nutritional density than MBs, and hence their environmental footprint per unit of nutrition was considerably lower across all 16 impact categories. Per Nutrient Density Unit, global warming, acidification, and land use burdens of PPBs were at least 89%, 87%, and 93% smaller, respectively, than MBs. Results were tested with Monte Carlo simulations and a modified null hypothesis significance test, which supported the main findings. Finally, when COC of land was factored in, the climate advantage of PPBs extended greatly. Assuming MBs equivalent to just 5% of German beef consumption are replaced by PPBs, total carbon savings including COC could amount to 8 million tonnes CO2e annually, an amount equal to 1% of Germany’s annual GHG emissions. Therefore, this study highlights the potential of PPBs to meet health and climate neutrality objectives.

Emergent constraints on transient climate response (TCR) and equilibrium climate sensitivity (ECS) from historical warming in CMIP5 and CMIP6 models

Abstract. Climate sensitivity to CO2 remains the key uncertainty in projections of future climate change. Transient climate response (TCR) is the metric of temperature sensitivity that is most relevant to warming in the next few decades and contributes the biggest uncertainty to estimates of the carbon budgets consistent with the Paris targets. Equilibrium climate sensitivity (ECS) is vital for understanding longer-term climate change and stabilisation targets. In the IPCC 5th Assessment Report (AR5), the stated “likely” ranges (16 %–84 % confidence) of TCR (1.0–2.5 K) and ECS (1.5–4.5 K) were broadly consistent with the ensemble of CMIP5 Earth system models (ESMs) available at the time. However, many of the latest CMIP6 ESMs have larger climate sensitivities, with 5 of 34 models having TCR values above 2.5 K and an ensemble mean TCR of 2.0±0.4 K. Even starker, 12 of 34 models have an ECS value above 4.5 K. On the face of it, these latest ESM results suggest that the IPCC likely ranges may need revising upwards, which would cast further doubt on the feasibility of the Paris targets. Here we show that rather than increasing the uncertainty in climate sensitivity, the CMIP6 models help to constrain the likely range of TCR to 1.3–2.1 K, with a central estimate of 1.68 K. We reach this conclusion through an emergent constraint approach which relates the value of TCR linearly to the global warming from 1975 onwards. This is a period when the signal-to-noise ratio of the net radiative forcing increases strongly, so that uncertainties in aerosol forcing become progressively less problematic. We find a consistent emergent constraint on TCR when we apply the same method to CMIP5 models. Our constraints on TCR are in good agreement with other recent studies which analysed CMIP ensembles. The relationship between ECS and the post-1975 warming trend is less direct and also non-linear. However, we are able to derive a likely range of ECS of 1.9–3.4 K from the CMIP6 models by assuming an underlying emergent relationship based on a two-box energy balance model. Despite some methodological differences; this is consistent with a previously published ECS constraint derived from warming trends in CMIP5 models to 2005. Our results seem to be part of a growing consensus amongst studies that have applied the emergent constraint approach to different model ensembles and to different aspects of the record of global warming.

The role of transport electrification in global climate change mitigation scenarios

Electrification is widely considered an attractive solution for reducing the oil dependency and environmental impact of road transportation. Many countries have been establishing increasingly stringent and ambitious targets in support of transport electrification. We conducted scenario simulations to depict the role of transport electrification in climate change mitigation and how the transport sector would interact with the energy-supply sector. The results showed that transport electrification without the replacement of fossil-fuel power plants leads to the unfortunate result of increasing emissions instead of achieving a low-carbon transition. While transport electrification alone would not contribute to climate change mitigation, it is interesting to note that switching to electrified road transport under the sustainable shared socioeconomic pathways permitted an optimistic outlook for a low-carbon transition, even in the absence of a decarbonized power sector. Another interesting finding was that the stringent penetration of electric vehicles can reduce the mitigation cost generated by the 2 °C climate stabilization target, implying a positive impact for transport policies on the economic system. With technological innovations such as electrified road transport, climate change mitigation does not have to occur at the expense of economic growth. Because a transport electrification policy closely interacts with energy and economic systems, transport planners, economists, and energy policymakers need to work together to propose policy schemes that consider a cross-sectoral balance for a green sustainable future.

Committing to Decarbonize

Climate targets are key for focusing global efforts to limit anthropogenic climate change. Yet, they induce a time-consistency problem in that current decision makers set (ambitious) targets and leave costly abatement to future generations. We develop a reduced-form climate-economy integrated assessment model, and compare naive and sophisticated climate policies. We also differentiate between immediate and durable emission reduction measures. Our findings demonstrate that naive decision makers consistently weaken climate stabilization targets, resulting in an equilibrium that misses the initial proposal. Sophisticated decision makers foresee the weakened outcome, and invest more in durable abatement measures in order to incentivize future decision makers to continue emission reduction efforts. Our results indicate that effective climate policy goes beyond the carbon price; it also involves strategic selection of abatement measures.

Energy system transition and macroeconomic impacts of a European decarbonization action towards a below 2\xa0\xb0C climate stabilization

The European Union has recently established the “Clean Energy for all Europeans” climate policy framework, aiming at the achievement of the European Nationally Determined Contribution (NDC) submitted to the Paris Agreement. The EU28 NDC includes a commitment for emission reductions in 2030 but also refers to an economy-wide effort towards 2050 so as to contribute effectively to the long-term mitigation of climate change. We discuss the respective EU28 emission pathways in the context of a well below 2 °C global climate stabilization target and estimate the macroeconomic impacts for the EU28 economy by considering alternative levels of climate action for major non-EU emitters. We employ two models, the technology-rich energy system model PRIMES, and the global large-scale hybrid computable general equilibrium model GEM-E3. The two models are soft linked so as to ensure a consistent and robust framework of analysis. We find that emission reductions in the energy supply sector are dominant up to 2030 while transport takes the lead in 2050. Transport and non-CO2 emissions are the main remaining emitting sources in 2050. We present the key decarbonization pillars and confirm that the impacts on the EU28 economy largely depend on the level of mitigation action adopted by the rest of the world and by the relative carbon intensity across regions. Due to asymmetric ambition of climate policies, a global implementation of NDCs results in economic losses for the EU28 when compared with a “pre-Paris” policy reference scenario, despite positive effects on energy-intensive and clean technology exports. On the contrary, we find that the region registers economic gains in the case of coordinated 2 °C global climate action.

Agricultural non-CO2 emission reduction potential in the context of the 1.5 °C target

Agricultural methane and nitrous oxide emissions represent around 10–12% of total anthropogenic GHG emissions and have a key role to play in achieving a 1.5 °C (above pre-industrial) climate stabilization target. Using a multi-model assessment approach, we quantify the potential contribution of agriculture to the 1.5 °C target and decompose the mitigation potential by emission source, region and mitigation mechanism. The results show that the livestock sector will be vital to achieve emission reductions consistent with the 1.5 °C target mainly through emission-reducing technologies or structural changes. Agriculture may contribute emission reductions of 0.8–1.4 Gt of CO2-equivalent (CO2e) yr−1 at just US$20 per tCO2e in 2050. Combined with dietary changes, emission reductions can be increased to 1.7–1.8 GtCO2e yr−1. At carbon prices compatible with the 1.5 °C target, agriculture could even provide average emission savings of 3.9 GtCO2e yr−1 in 2050, which represents around 8% of current GHG emissions. Agricultural CH4 and N2O emissions represent around 11% of total anthropogenic GHGs. Here agriculture mitigation potentials are quantified, in the context of the 1.5 °C target, and decomposed by emission source, region and mitigation mechanism.

Urban carbon mapping: Towards a standardized framework

Cities are responsible for a large share of global energy consumption and CO2 emissions. Significant reduction of urban energy consumption and CO2 emissions is essential for meeting the ambitious climate stabilization targets. This hinges on having adequate understanding of the patterns and trends of emissions. It is essential to create datasets of cities emissions and utilize mapping techniques to inform planners and decision makers about the dynamics of urban carbon emissions. Due to the openness of cities and issues related to availability and accessibility of urban energy consumption data, this is a challenging task. It is critical to develop consistent methods for mapping emissions. Such methods and frameworks should enable cities to map their emissions with minimum data requirements. They should also be applicable to different cities across the world. As a preliminary effort, this study introduces a framework for synthesizing building and transport energy consumption data with the Local Climate Zones (LCZs) classification system. Drawing on preliminary results from applying the framework to Bangkok, Shanghai, and Tokyo, we explain how this approach can provide opportunities for standardizing urban carbon accounting. The paper concludes with suggestions for improving granularity and accuracy of emissions accounting. The concept of Local Energy Zones (LEZs) is introduced and is suggested to be used as a potentially suitable concept for analysing CO2 emissions dynamics of cities.

An Assessment of Near-to-Mid-Term Economic Impacts and Energy Transitions under “2 °C” and “1.5 °C” Scenarios for India

The goal of limiting global temperature rise to “well below” 2 °C has been reaffirmed in the Paris Agreement on climate change at the 21st Conference of the Parties (COP21). Almost all countries submitted their decarbonization targets in their Intended Nationally Determined Contributions (INDC) to the United Nations Framework Convention on Climate Change (UNFCCC) and India did as well. India’s nationally determined contribution (NDC) aims to reduce greenhouse gas (GHG) emissions intensity of national GDP in 2030 by 33–35% compared to 2005. This paper analyzes how India’s NDC commitments compare with emission trajectories consistent with well below 2 °C and 1.5 °C global temperature stabilization goals. A top-down computable general equilibrium model is used for the analysis. Our analysis shows that there are significant emission gaps between NDC and global climate stabilization targets in 2030. The energy system requires significant changes, mostly relying on renewable energy and carbon capture and storage (CCS) technology. The mitigation costs would increase if India delays its abatement efforts and is locked into NDC pathways till 2030. India’s GHG emissions would peak 10 years earlier under 1.5 °C global temperature stabilization compared to the 2 °C goal. The results imply that India would need financial and technological support from developed countries to achieve emissions reductions aligned with the global long-term goal.

Climate shifts within major agricultural seasons for +1.5 and +2.0 °C worlds: HAPPI projections and AgMIP modeling scenarios

This study compares climate changes in major agricultural regions and current agricultural seasons associated with global warming of +1.5 or +2.0 °C above pre-industrial conditions. It describes the generation of climate scenarios for agricultural modeling applications conducted as part of the Agricultural Model Intercomparison and Improvement Project (AgMIP) Coordinated Global and Regional Assessments. Climate scenarios from the Half a degree Additional warming, Projections, Prognosis and Impacts project (HAPPI) are largely consistent with transient scenarios extracted from RCP4.5 simulations of the Coupled Model Intercomparison Project phase 5 (CMIP5). Focusing on food and agricultural systems and top-producing breadbaskets in particular, we distinguish maize, rice, wheat, and soy season changes from global annual mean climate changes. Many agricultural regions warm at a rate that is faster than the global mean surface temperature (including oceans) but slower than the mean land surface temperature, leading to regional warming that exceeds 0.5 °C between the +1.5 and +2.0 °C Worlds. Agricultural growing seasons warm at a pace slightly behind the annual temperature trends in most regions, while precipitation increases slightly ahead of the annual rate. Rice cultivation regions show reduced warming as they are concentrated where monsoon rainfall is projected to intensify, although projections are influenced by Asian aerosol loading in climate mitigation scenarios. Compared to CMIP5, HAPPI slightly underestimates the CO2 concentration that corresponds to the +1.5 °C World but overestimates the CO2 concentration for the +2.0 °C World, which means that HAPPI scenarios may also lead to an overestimate in the beneficial effects of CO2 on crops in the +2.0 °C World. HAPPI enables detailed analysis of the shifting distribution of extreme growing season temperatures and precipitation, highlighting widespread increases in extreme heat seasons and heightened skewness toward hot seasons in the tropics. Shifts in the probability of extreme drought seasons generally tracked median precipitation changes; however, some regions skewed toward drought conditions even where median precipitation changes were small. Together, these findings highlight unique seasonal and agricultural region changes in the +1.5 °C and +2.0 °C worlds for adaptation planning in these climate stabilization targets.

Adjusting Mitigation Pathways to Stabilize Climate at 1.5°C and 2.0°C Rise in Global Temperatures to Year 2300

AbstractTo avoid the most dangerous consequences of anthropogenic climate change, the Paris Agreement provides a clear and agreed climate mitigation target of stabilizing global surface warming to under 2.0°C above preindustrial, and preferably closer to 1.5°C. However, policy makers do not currently know exactly what carbon emissions pathways to follow to stabilize warming below these agreed targets, because there is large uncertainty in future temperature rise for any given pathway. This large uncertainty makes it difficult for a cautious policy maker to avoid either: (1) allowing warming to exceed the agreed target or (2) cutting global emissions more than is required to satisfy the agreed target, and their associated societal costs. This study presents a novel Adjusting Mitigation Pathway (AMP) approach to restrict future warming to policy‐driven targets, in which future emissions reductions are not fully determined now but respond to future surface warming each decade in a self‐adjusting manner. A large ensemble of Earth system model simulations, constrained by geological and historical observations of past climate change, demonstrates our self‐adjusting mitigation approach for a range of climate stabilization targets ranging from 1.5°C to 4.5°C, and generates AMP scenarios up to year 2300 for surface warming, carbon emissions, atmospheric CO2, global mean sea level, and surface ocean acidification. We find that lower 21st century warming targets will significantly reduce ocean acidification this century, and will avoid up to 4 m of sea‐level rise by year 2300 relative to a high‐end scenario.

STRATEGIC DYNAMIC CLIMATE POLICY: THE ROLE OF CCS

Normal 0 21 false false false TR JA X-NONE /* Style Definitions */ table.MsoNormalTable {mso-style-name:Normal Tablo; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-parent:; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin:0cm; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:10.0pt; font-family:Calibri;} The paper examines the role of carbon capture and storage (CCS) technology first in an exogenous, and then, in an endogenous growth model with environmental constraints. In the first part, we investigate the activity of the CCS systems given an exhaustible resource constraint and limited CO 2 storage capacity under climate stabilization targets. In the second section, we look at the activity of the CCS technology and corresponding research and development (R&D) investments. Our findings indicate that the CCS technology is welfare improving but its level of activity is highly affected by resource and storage constraints. Given the low amount of resources allocated for CCS R&D, it can be considered that learning-by-doing (LbD) is more relevant for the CCS technology. This is because all components of CCS systems exist and are in use today by the fossil fuel extraction and refining industries. Yet, CCS has not been applied at scale to a large and operational commercial fossil fuel power plant, indicating that the technology can significantly benefit from LbD. Uncertainties in the political will towards tax rates, and leakage possibilities of the stored CO 2 are issues that are left for further research.

Cost-effective architecture of carbon capture and storage (CCS) grid in India

Various modeling studies analyzing global 2°C climate stabilization scenarios have projected penetration of CO2 capture and storage (CCS) technologies in India alongside a sizable penetration of renewable energy technologies. The assessments of geological storage potential over India have shown wide variation across regions. This paper examines the locations of large point sources of CO2 emissions in India and matches it with carbon storage locations to minimize the cost of CCS evolving grid. The concept of weighted Euclidean distance and Integrated Environmental Control Model are used to propose suitable pipeline networks for emissions-intensive clusters to optimize the cost of CO2 avoidance. The computational method estimates proximate storage location for each CO2 emitting source taking into account the total storage potential at each location. CCS requirement in India would vary depending on the global climate stabilization target. We examine two targets for India that correspond to 2°C and well below 2°C global mitigation regimes. According to our estimates, India could mitigate around 780 Mt CO2 per year below 60$/t-CO2 (2005 prices) over 30 years, and another 250 Mt CO2 per year for up to 75$/t-CO2 prices through CCS under these scenarios respectively.

Decarbonization Pathways in Southeast Asia: New Results for Indonesia, Malaysia, Philippines, Thailand and Viet Nam

Southeast Asia is one of the most vulnerable regions of the world to the impacts of climate change. At the same time, the region is also following a trajectory that could make it a major contributor to greenhouse gas emissions in the future. Understanding the economic implications of policy options for low carbon growth is essential to formulate instruments that achieve the greatest emissions reductions at lowest cost. This study focuses on five developing countries of Southeast Asia that collectively account for 90% of regional emissions in recent years—Indonesia, Malaysia, the Philippines, Thailand, and Viet Nam. The analyses are based on the CGE economy-energy-environment model ICES under an array of scenarios reflecting business as usual, fragmented climate policies, an approximately 2.4°C post 2020 global climate stabilization target, termed 650 parts per million (ppm) carbon dioxide (CO2) equivalent (eq), and an approximately 2°C global target (termed 500 ppm CO2 eq). Averted deforestation through reducing emissions from forest degradation and deforestation (REDD) is included in some scenarios. The study shows that global and coordinated action is found to be critical to the cost effectiveness of emissions stabilization policies. A 650ppm stabilization scenario (below 3°C in 2100) has a similar cost to the region to current fragmented targets, but achieves much higher levels of emissions reductions. However, only some of the countries have short-term emissions targets that are consistent with a stabilization scenario at 650ppm: these are Indonesia, Philippines and Viet Nam. None of the countries’ mid-term targets are coherent with more ambitious stabilization scenario at 500ppm.

Quantifying uncertainty in future ocean carbon uptake

AbstractAttributing uncertainty in ocean carbon uptake between societal trajectory (scenarios), Earth System Model construction (structure), and inherent natural variation in climate (internal) is critical to make progress in identifying, understanding, and reducing those uncertainties. In the present issue of Global Biogeochemical Cycles, Lovenduski et al. (2016) disentangle these drivers of uncertainty in ocean carbon uptake over time and space and assess the resulting implications for the emergence timescales of structural and scenario uncertainty over internal variability. Such efforts are critical for establishing realizable and efficient monitoring goals and prioritizing areas of continued model development. Under recently proposed climate stabilization targets, such efforts to partition uncertainty also become increasingly critical to societal decision‐making in the context of carbon stabilization.

The Paris Agreement and the inherent inconsistency of climate policymaking

Since the adoption of the Paris Agreement, the actual meaning of many crucial aspects of that agreement still remains fairly unclear. This has lead to extensive framing efforts, for example on the 5‐year review mechanism. What has been largely overlooked, however, are the decisions on quantified climate stabilization targets. Until now, there has been no serious questioning of the intention to limit the temperature increase to 2 or even 1.5 °C. Not that many in the climate research community seem to grasp the political rationalities behind the setting of long‐term policy targets. Even the mainstream policy discourse assumes consistency between talk, decisions, and actions. Accordingly, a decision on a certain climate target is presented and perceived as an act of deliberate choice, that will be followed up with the deployment of appropriate measures. In real‐world policymaking, however, many decisions are viewed as independent organizational products, not necessarily requiring appropriate action. Despite the cultural norm of consistency, inconsistency is an inherent and inevitable feature of policymaking. This is particularly problematic in public domains with a deliberately transformative agenda like climate policy, which is characterized by long‐term planning and a high demand for scientific advice. But if consistency of talk, decisions, and actions cannot be assumed, then concepts like evidence‐based policymaking become essentially devoid of meaning. Simply delivering the best available knowledge to policymakers might even have counterintuitive effects. In the future, policy‐driven climate researchers and advisors must critically assess how their work is actually being interpreted and used in policymaking processes. WIREs Clim Change 2016, 7:790–797. doi: 10.1002/wcc.427This article is categorized under: Policy and Governance > International Policy Framework

Simulating the Earth system response to negative emissions

Natural carbon sinks currently absorb approximately half of the anthropogenic CO2 emitted by fossil fuel burning, cement production and land-use change. However, this airborne fraction may change in the future depending on the emissions scenario. An important issue in developing carbon budgets to achieve climate stabilisation targets is the behaviour of natural carbon sinks, particularly under low emissions mitigation scenarios as required to meet the goals of the Paris Agreement. A key requirement for low carbon pathways is to quantify the effectiveness of negative emissions technologies which will be strongly affected by carbon cycle feedbacks. Here we find that Earth system models suggest significant weakening, even potential reversal, of the ocean and land sinks under future low emission scenarios. For the RCP2.6 concentration pathway, models project land and ocean sinks to weaken to 0.8 ± 0.9 and 1.1 ± 0.3 GtC yr−1 respectively for the second half of the 21st century and to −0.4 ± 0.4 and 0.1 ± 0.2 GtC yr−1 respectively for the second half of the 23rd century. Weakening of natural carbon sinks will hinder the effectiveness of negative emissions technologies and therefore increase their required deployment to achieve a given climate stabilisation target. We introduce a new metric, the perturbation airborne fraction, to measure and assess the effectiveness of negative emissions.