Quantifying non-CO2 contributions to remaining carbon budgets

The IPCC Special Report on 1.5&#176;C concluded that the maximum level of anthropogenic global warming is &#8220;determined by cumulative net global anthropogenic CO2 emissions up to the time of net zero CO2 emissions and the level of non-CO2 radiative forcing&#8221; in the decades prior to the time of peak warming. Here we quantify this statement, using CO2-forcing-equivalent (CO2-fe) emissions to calculate remaining carbon budgets without treating available mitigation scenarios as a representative sample of possible futures.CO2-fe emissions are used to calculate an observationally-constrained estimate of the Transient Climate Response to cumulative Emissions (TCRE) using a large ensemble of historical radaitve forcing timeseries. This observationally-constrained TCRE is used to calculate remaining total CO2-fe budgets from 2018 to 1.5&#176;C, which we compare with results discussed in Chapter 2, SR15. We consider contributions to this total remaining budget from CO2 and non-CO2 sources using both historical observations and the available mitigation scenarios in the IAMC scenario database.We calculate remaining CO2 budgets for a 33, 50 or 66% chance of limiting peak warming to 1.5&#176;C and use these to assess the extent to which scenarios in the IAMC scenario database are consistent with ambitious mitigation as outlined in the Paris Agreement. We argue that, assuming no change in the definition of observed global warming and no increase in TCRE due to non-linear feedbacks, scenarios currently classified as &#8220;lower 2&#176;C-compatible&#8221; are consistent with a best-estimate peak warming of 1.5&#176;C.

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Quantifying non-CO2 contributions to remaining carbon budgets

npj Climate and Atmospheric Science ◽

10.1038/s41612-021-00203-9 ◽

2021 ◽

Vol 4 (1) ◽

Author(s):

Stuart Jenkins ◽

Michelle Cain ◽

Pierre Friedlingstein ◽

Nathan Gillett ◽

Tristram Walsh ◽

...

Keyword(s):

Global Warming ◽

Confidence Interval ◽

Carbon Emissions ◽

Radiative Forcing ◽

Two Dimensional ◽

Climate Response ◽

Carbon Budgets ◽

Special Report ◽

Transient Climate Response ◽

The Impact

AbstractThe IPCC Special Report on 1.5 °C concluded that anthropogenic global warming is determined by cumulative anthropogenic CO2 emissions and the non-CO2 radiative forcing level in the decades prior to peak warming. We quantify this using CO2-forcing-equivalent (CO2-fe) emissions. We produce an observationally constrained estimate of the Transient Climate Response to cumulative carbon Emissions (TCRE), giving a 90% confidence interval of 0.26–0.78 °C/TtCO2, implying a remaining total CO2-fe budget from 2020 to 1.5 °C of 350–1040 GtCO2-fe, where non-CO2 forcing changes take up 50 to 300 GtCO2-fe. Using a central non-CO2 forcing estimate, the remaining CO2 budgets are 640, 545, 455 GtCO2 for a 33, 50 or 66% chance of limiting warming to 1.5 °C. We discuss the impact of GMST revisions and the contribution of non-CO2 mitigation to remaining budgets, determining that reporting budgets in CO2-fe for alternative definitions of GMST, displaying CO2 and non-CO2 contributions using a two-dimensional presentation, offers the most transparent approach.

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The relationship between net GHG emissions and radiative forcing with an application to Article 4.1 of the Paris Agreement.

10.21203/rs.3.rs-1022455/v1 ◽

2021 ◽

Author(s):

Tom M. L. Wigley

Keyword(s):

Global Warming ◽

Radiative Forcing ◽

Ghg Emissions ◽

Zero Point ◽

Paris Agreement ◽

Test Case ◽

Net Zero ◽

Global Warming Potentials ◽

The Relationship

Abstract This paper provides an assessment of Article 4.1 of the Paris Agreement on climate; the main goal of which is to provide guidance on how “to achieve the long-term temperature goal set out in Article 2”. Paraphrasing, Article 4.1 says that, to achieve this end, we should decrease greenhouse gas (GHG) emissions so that net anthropogenic GHG emissions fall to zero in the second half of this century. To aggregate net GHG emissions, 100-year Global Warming Potentials (GWP-100) are commonly used to convert non-CO2 emissions to equivalent CO2 emissions. As a test case using methane, temperature projections using GWP-100 scaling are shown to be seriously in error. This throws doubt on the use of GWP-100 scaling to estimate net GHG emissions. An alternative method to determine the net-zero point for GHG emissions based on radiative forcing is derived. This shows that the net-zero point needs to be reached as early as 2036, much sooner than in the Article 4.1 window. Other scientific flaws in Article 4.1 that further undermine its purpose to guide efforts to achieve the Article 2 temperature targets are discussed.

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An integrated approach to quantifying uncertainties in the remaining carbon budget

Communications Earth & Environment ◽

10.1038/s43247-020-00064-9 ◽

2021 ◽

Vol 2 (1) ◽

Author(s):

H. Damon Matthews ◽

Katarzyna B. Tokarska ◽

Joeri Rogelj ◽

Christopher J. Smith ◽

Andrew H. MacDougall ◽

...

Keyword(s):

Global Warming ◽

Carbon Budget ◽

Integrated Approach ◽

Observational Constraints ◽

Climate Response ◽

Carbon Budgets ◽

Transient Climate Response ◽

Median Estimate ◽

Emissions Scenarios ◽

Climate Influences

AbstractThe remaining carbon budget quantifies the future CO2 emissions to limit global warming below a desired level. Carbon budgets are subject to uncertainty in the Transient Climate Response to Cumulative CO2 Emissions (TCRE), as well as to non-CO2 climate influences. Here we estimate the TCRE using observational constraints, and integrate the geophysical and socioeconomic uncertainties affecting the distribution of the remaining carbon budget. We estimate a median TCRE of 0.44 °C and 5–95% range of 0.32–0.62 °C per 1000 GtCO2 emitted. Considering only geophysical uncertainties, our median estimate of the 1.5 °C remaining carbon budget is 440 GtCO2 from 2020 onwards, with a range of 230–670 GtCO2, (for a 67–33% chance of not exceeding the target). Additional socioeconomic uncertainty related to human decisions regarding future non-CO2 emissions scenarios can further shift the median 1.5 °C remaining carbon budget by ±170 GtCO2.

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The relationship between net GHG emissions and radiative forcing with an application to Article 4.1 of the Paris Agreement

Climatic Change ◽

10.1007/s10584-021-03249-z ◽

2021 ◽

Vol 169 (1-2) ◽

Author(s):

Tom M. L. Wigley

Keyword(s):

Global Warming ◽

Radiative Forcing ◽

Ghg Emissions ◽

Zero Point ◽

Paris Agreement ◽

Scaling Method ◽

Net Zero ◽

Global Warming Potentials ◽

The Relationship

AbstractThis paper provides an assessment of Article 4.1 of the Paris Agreement on climate; the main goal of which is to provide guidance on how “to achieve the long-term temperature goal set out in Article 2”. Paraphrasing, Article 4.1 says that, to achieve this end, we should decrease greenhouse gas (GHG) emissions so that net anthropogenic GHG emissions fall to zero in the second half of this century. To aggregate net GHG emissions, 100-year global warming potentials (GWP-100) are commonly used to convert non-CO2 emissions to equivalent CO2 emissions. The GWP-scaling method is tested using methane as an example. The temperature projections using GWP-100 scaling are shown to be seriously in error. This throws doubt on the use of GWP-100 scaling to estimate net GHG emissions. An alternative method to determine the net-zero point for GHG emissions based on radiative forcing is derived, where the net-zero point is identified with the maximum of GHG forcing. This shows that, to meet the Article 2 warming goal, the net-zero point for GHG emissions needs to be reached as early as 2036, much sooner than in the Article 4.1 window. Other scientific problems in Article 4.1 that further undermine its purpose to guide efforts to achieve the Article 2 temperature targets are discussed.

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Greenhouse gas metrics for net zero targets in science and policy

10.5194/egusphere-egu21-10816 ◽

2021 ◽

Author(s):

Alexander Nauels ◽

Carl-Friedrich Schleussner ◽

Joeri Rogelj

Keyword(s):

Global Warming ◽

Radiative Forcing ◽

National Level ◽

National Policy ◽

Paris Agreement ◽

Climate Effect ◽

Science And Policy ◽

Net Zero ◽

Global Warming Potentials ◽

Metric Selection

The treatment of non-CO2 greenhouse gases is central for scientific assessments of effective climate change mitigation and climate policy. Radiative forcing of a unit of emitted short-lived gases decays quickly; on the order of a decade for methane, as opposed to centuries for CO2. Metric selection for comparing the climate effect of these emissions with CO2 thereby comes with choices regarding short- vs. long-term priorities to achieve mitigation. The global nature of the well-mixed atmosphere also has implications for the transferability of concepts such as global warming potentials from the global to the national scale.Here we present the implications of metric choice on global emissions balance and net zero, with a particular emphasis on the consistency with the wider context of the Paris Agreement, both on the global as well as the national level. Stylized scenarios show that interpreting the Paris Agreement emissions goals with metrics different from the IPCC AR5 can lead to inconsistencies with the Agreement&#8217;s temperature goal. Furthermore, we illustrate that introducing metrics that depend on historical emissions in a national context raises profound questions of equity and fairness, thereby questioning the applicability of non-constant global warming potentials at any but the global level. We provide suggestions to adequately approach these issues in the context of the Paris Agreement and national policy making.

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Global opportunities and challenges on net-zero CO2 emissions towards a sustainable future

Reaction Chemistry & Engineering ◽

10.1039/d1re00233c ◽

2021 ◽

Author(s):

Joseph A Nathanael ◽

Kumaran Kannaiyan ◽

Aruna K. Kunhiraman ◽

Seeram Ramakrishna ◽

Vignesh Kumaravel

Keyword(s):

Global Warming ◽

Co2 Emissions ◽

Co2 Capture ◽

Sustainable Future ◽

Net Zero ◽

And Storage

In recent years, global warming has been showing its deadliest impact on civilization through natural calamities. Given this situation, the sustainable and economically viable CO2 capture, utilization, and storage (CCUS)...

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Emergent Constraints on Climate-Carbon Cycle Projections

10.5194/egusphere-egu2020-19469 ◽

2020 ◽

Author(s):

Peter Cox

Keyword(s):

Carbon Cycle ◽

Radiative Forcing ◽

Full Range ◽

Future Climate ◽

Climate Projections ◽

Carbon Budgets ◽

Transient Climate Response ◽

Cycle System ◽

Wide Range ◽

Emergent Constraints

Earth System Models (ESMs) are designed to project changes in the climate-carbon cycle system over the coming centuries. These models agree that the climate will change significantly under feasible scenarios of future CO2emissions. However, model projections still cover a wide range for any given scenario, which impedes progress on tackling climate change. Estimates of the Transient Climate Response to Emissions (TCRE), and therefore of remaining carbon budgets, are affected by uncertainties in the response of land and ocean carbon sinks to changes in climate and CO2, and also by continuing uncertainties in the sensitivity of climate to radiative forcing. Over the last 7 years Emergent Constraints have been proposed on many of the key uncertainties. Emergent constraints use the full range of model behaviours to find relationships between measureable aspects of present and past climates, and future climate projections. This presentation will summarise proposed emergent constraints of relevance to future climate-carbon cycle projections, and discuss the implications for the remaining carbon budgets for stabilisation at 1.5K and 2K.

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Effect of Urban Heat Island and Global Warming Countermeasures on Heat Release and Carbon Dioxide Emissions from a Detached House

Atmosphere ◽

10.3390/atmos12050572 ◽

2021 ◽

Vol 12 (5) ◽

pp. 572

Author(s):

Daisuke Narumi ◽

Ronnen Levinson ◽

Yoshiyuki Shimoda

Keyword(s):

Carbon Dioxide ◽

Global Warming ◽

Heat Release ◽

Urban Heat Island ◽

Co2 Emissions ◽

Heat Island ◽

Sensible Heat ◽

Heating Season ◽

Urban Heat ◽

Cooling Effects

Urban air temperature rises induced by the urban heat island (UHIE) effect or by global warming (GW) can be beneficial in winter but detrimental in summer. The SCIENCE-Outdoor model was used to simulate changes to sensible heat release and CO2 emissions from buildings yielded by four UHIE countermeasures and five GW countermeasures. This model can evaluate the thermal condition of building envelope surfaces, both inside and outside. The results showed that water-consuming UHIE countermeasures such as evaporative space cooling and roof water showering provided positive effects (decreasing sensible heat release and CO2 emissions related to space conditioning) in summer. Additionally, they had no negative (unwanted cooling) effects in winter since they can be turned off in the heating season. Roof greening can provide the greatest space- conditioning CO2 emissions reductions among four UHIE countermeasures, and it reduces the amount of heat release slightly in the heating season. Since the effect on reducing carbon dioxide (CO2) emissions by UHIE countermeasures is not very significant, it is desirable to introduce GW countermeasures in order to reduce CO2 emissions. The significance of this study is that it constructed the new simulation model SCIENCE-Outdoor and applied it to show the influence of countermeasures upon both heat release and CO2 emissions.

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A Link between the Hiatus in Global Warming and North American Drought

Journal of Climate ◽

10.1175/jcli-d-14-00616.1 ◽

2015 ◽

Vol 28 (9) ◽

pp. 3834-3845 ◽

Cited By ~ 69

Author(s):

Thomas L. Delworth ◽

Fanrong Zeng ◽

Anthony Rosati ◽

Gabriel A. Vecchi ◽

Andrew T. Wittenberg

Keyword(s):

Global Warming ◽

North America ◽

Surface Temperature ◽

North American ◽

Radiative Forcing ◽

Tropical Pacific ◽

Global Warming Hiatus ◽

Warming Hiatus ◽

The Impact ◽

The Tropical Pacific

Abstract Portions of western North America have experienced prolonged drought over the last decade. This drought has occurred at the same time as the global warming hiatus—a decadal period with little increase in global mean surface temperature. Climate models and observational analyses are used to clarify the dual role of recent tropical Pacific changes in driving both the global warming hiatus and North American drought. When observed tropical Pacific wind stress anomalies are inserted into coupled models, the simulations produce persistent negative sea surface temperature anomalies in the eastern tropical Pacific, a hiatus in global warming, and drought over North America driven by SST-induced atmospheric circulation anomalies. In the simulations herein the tropical wind anomalies account for 92% of the simulated North American drought during the recent decade, with 8% from anthropogenic radiative forcing changes. This suggests that anthropogenic radiative forcing is not the dominant driver of the current drought, unless the wind changes themselves are driven by anthropogenic radiative forcing. The anomalous tropical winds could also originate from coupled interactions in the tropical Pacific or from forcing outside the tropical Pacific. The model experiments suggest that if the tropical winds were to return to climatological conditions, then the recent tendency toward North American drought would diminish. Alternatively, if the anomalous tropical winds were to persist, then the impact on North American drought would continue; however, the impact of the enhanced Pacific easterlies on global temperature diminishes after a decade or two due to a surface reemergence of warmer water that was initially subducted into the ocean interior.

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