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Cited by 266Climate variability and modelsClimate Change Policy and EconomicsClimate Change and Environmental Impact

The DOI matches its Crossref record; 191 of the 192 references it cites were found in a registry or an index, and 1 are not checked yet; none of the 169 sources its claims cite is checked for support yet.

Young people's burden: requirement of negative CO 2 emissions

Open access
Hansen, James, Sato, Makiko, Kharecha, Pushker, von Schuckmann, Karina, Beerling, David J., Cao, Junji, Marcott, Shaun, Masson-Delmotte, Valerie, Prather, Michael J., Rohling, Eelco J., Shakun, Jeremy, Smith, Pete, Lacis, Andrew, Russell, Gary, Ruedy, Reto·2017·Earth System Dynamics
DOI 10.5194/esd-8-577-2017

Published version of a preprint

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Abstract

Abstract. Global temperature is a fundamental climate metric highly correlated with sea level, which implies that keeping shorelines near their present location requires keeping global temperature within or close to its preindustrial Holocene range. However, global temperature excluding short-term variability now exceeds +1 °C relative to the 1880–1920 mean and annual 2016 global temperature was almost +1.3 °C. We show that global temperature has risen well out of the Holocene range and Earth is now as warm as it was during the prior (Eemian) interglacial period, when sea level reached 6–9 m higher than today. Further, Earth is out of energy balance with present atmospheric composition, implying that more warming is in the pipeline, and we show that the growth rate of greenhouse gas climate forcing has accelerated markedly in the past decade. The rapidity of ice sheet and sea level response to global temperature is difficult to predict, but is dependent on the magnitude of warming. Targets for limiting global warming thus, at minimum, should aim to avoid leaving global temperature at Eemian or higher levels for centuries. Such targets now require negative emissions, i.e., extraction of CO2 from the air. If phasedown of fossil fuel emissions begins soon, improved agricultural and forestry practices, including reforestation and steps to improve soil fertility and increase its carbon content, may provide much of the necessary CO2 extraction. In that case, the magnitude and duration of global temperature excursion above the natural range of the current interglacial (Holocene) could be limited and irreversible climate impacts could be minimized. In contrast, continued high fossil fuel emissions today place a burden on young people to undertake massive technological CO2 extraction if they are to limit climate change and its consequences. Proposed methods of extraction such as bioenergy with carbon capture and storage (BECCS) or air capture of CO2 have minimal estimated costs of USD 89–535 trillion this century and also have large risks and uncertain feasibility. Continued high fossil fuel emissions unarguably sentences young people to either a massive, implausible cleanup or growing deleterious climate impacts or both.

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Overview

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Written from the paper’s full text.

TL;DR

Global temperature has risen out of the Holocene range and is now comparable to the Eemian, when sea level was 6–9 m higher, while Earth remains out of energy balance and GHG forcing growth has accelerated. Limiting warming to 1.5 °C or returning CO₂ to 350 ppm now requires negative CO₂ emissions; if high fossil fuel emissions continue, young people face massive technological CO₂ extraction with estimated costs of USD 89–535 trillion this century.

Key findings

  • Global temperature excluding short-term variability exceeds +1 °C relative to the 1880–1920 mean, and annual 2016 was almost +1.3 °C; Earth is now as warm as the Eemian, when sea level reached 6–9 m higher than today.
  • Earth is out of energy balance: upper-2000 m ocean heat uptake averaged 0.7 W m⁻² over 2005–2015, and the total imbalance is +0.75 ± 0.25 W m⁻² averaged over the solar cycle.
  • GHG climate forcing growth has accelerated: the annual increment increased by more than 20 % in just the past 5 years; atmospheric CO₂ growth rose from less than 1 ppm yr⁻¹ 50 years ago to more than 2 ppm yr⁻¹ today, and CH₄ growth averaged 10 ppb yr⁻¹ in 2014–2016.
  • Negative emissions are required. To reach 350 ppm CO₂ in 2100, scenarios with −6 and −3 % yr⁻¹ emission reductions require 153 and 237 PgC extraction, while constant emissions and +2 % yr⁻¹ growth require 695 and 1630 PgC; technological extraction costs are estimated at USD 89–535 trillion this century for continued high emissions.

Methods

  • The paper combines modern GISTEMP instrumental temperature data, Holocene and Eemian paleoclimate reconstructions, Argo-era ocean heat content for 2005–2015, and observed CO₂/CH₄ records.
  • It uses a simple Green’s function climate model with equilibrium fast-feedback climate sensitivity of 0.75 °C (W m⁻²)⁻¹ (3 °C for 2 × CO₂), the Bern carbon cycle model, and emission scenarios of −6, −3, constant, and +2 % yr⁻¹, plus RCP scenarios and CO₂-extraction cases targeting 350 or 450 ppm in 2100.
  • The analysis is presented as transparent to non-scientists, with tabulated forcings and defining data so calculations can be repeated with alternative choices.

Limitations

  • The paper states that precise specification of slow-feedback magnitude and timescales is not possible, and that its climate calculations include only fast feedbacks; this limitation may soon become important as warming exceeds the Holocene range.
  • It states important uncertainties in climate sensitivity, ocean mixing and dynamics, aerosol forcing, and CO₂ extraction and mitigation cost estimates; it also notes that large-scale negative emissions have uncertain feasibility and large risks.
  • Evident from the text: the conclusions depend on a simple climate/carbon-cycle model and assumed sensitivity, and the paper does not estimate the cost of CO₂ extraction via improved agricultural and forestry practices.

Model-written summary. Check it against the paper before relying on it.

Integrity signals

Registry

Crossref · 10.5194/esd-8-577-2017

Cites

191 of 192 references verified0 citation errors · 0 not checkable

Statistics

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Verification

Claims the paper makes

0 of 169 cited sources checked · 0 supported · 0 flagged

  • Probably not a substantial claim. 49
  • It may state two separate claims as one. 98
  • The quote only partly states this claim. 1
130 of 130

  • The authors state this as an assumption.

    The 1880-1920 mean temperature is 0.1°C warmer than the Little Ice Age minimum.

    “Concatenation of the modern and Holocene temperature records (Fig. 3; Appendix A5) assumes that 1880-1920 mean temperature is 0.1 • C warmer than the Little Ice Age minimum (Abram et al., 2016).”

  • The authors state this as an assumption.

    Maximum Eemian temperature was +1°C relative to preindustrial with an uncertainty of at least 0.5°C.

    “we assume that maximum Eemian temperature was +1 • C relative to preindustrial with an uncertainty of at least 0.5 • C.”

  • The authors state this as an assumption.

    Improved practices will aim at optimizing agricultural and forest carbon uptake via relatively natural approaches, compatible with the land delivering a range of ecosystem services.

    “We assume that improved practices will aim at optimizing agricultural and forest carbon uptake via relatively natural approaches, compatible with the land delivering a range of ecosystem services (Smith, 2016;Smith et al., 2016).”

  • The authors state this as an assumption.

    Aerosol plus surface albedo forcing is -1.5 W m-2 in 2100.

    “We assume a small increase this century as global population rises and increasing aerosol emission controls in emerging economies tend to be offset by increasing development elsewhere, so aerosol + surface forcing is -1.5 W m -2 in 2100.”

  • The authors state this as an assumption.

    100 PgC can be stored via improved agricultural and forestry practices.

    “Cost estimates here for extraction use amounts 100 Pg less than in Fig. 10 under assumption that 100 PgC can be stored via improved agricultural and forestry practices.”

  • The paper relies on this without support.

    Human population continues to grow.

    “Given that human population continues to grow, and that human-caused climate effects such as increased desertification can lead to increased aerosols, we do not anticipate a large reduction in the aerosol cooling effect, even if fossil fuel use declines.”

  • The paper relies on this without support.

    Human-caused climate effects such as increased desertification can lead to increased aerosols.

    “Given that human population continues to grow, and that human-caused climate effects such as increased desertification can lead to increased aerosols, we do not anticipate a large reduction in the aerosol cooling effect, even if fossil fuel use declines.”

  • The authors state this as an assumption.

    Emissions will continue at approximately current levels until a global program of emission reductions begins in 4 years (in 2021 relative to 2020).

    “Required extraction is at least ∼ 150 PgC in our updated scenarios, which incorporate growth of emissions in the past 4 years and assume that emissions will continue at approximately current levels until a global program of emission reductions begins in 4 years (in 2021 relative to 2020; see Figs. 9 and 10 for reduction rates).”
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Claims other papers make about this one

Each is checked against this paper’s own text: does it say what the citing paper says it does?

Self-check

Percentages, sums and reported differences re-computed from the paper’s own numbers.

Each contradiction between two passages listed here was confirmed by an independent check.

  • Conflicting start dates for CO 2 extraction

    Major

    The text says extraction increases from zero in 2010 in all cases, while the Figure 10 caption says it increases after 2020, or after 2015 in the +2 % case.

  • Reference publication year precedes the period in its title

    Minor

    The reference is dated 1973, but its title describes changes since 1980. A 1973 publication could not assess that later period.

2 of 2

Citations

Cites

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Research works printed but not linked: 18

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Metadata

Authors
Hansen, J., Sato, M., Kharecha, P., von Schuckmann, K., Beerling, D. J., Cao, J., Marcott, S., Masson-Delmotte, V., Prather, M. J., Rohling, E. J., Shakun, J., Smith, P., Lacis, A., Russell, G., & Ruedy, R.
Affiliations
  • Columbia University (US)
  • Leverhulme Centre for Climate Change Mitigation (GB)
  • Institute of Earth Environment (CN)
  • University of Wisconsin–Madison (US)
  • University of California, Irvine (US)
  • Australian National University (AU)
  • Boston College (US)
  • University of Aberdeen (GB)
  • Goddard Institute for Space Studies (US)
Corresponding author
Hansen, James
ORCID
Venue
Earth System Dynamics
Publisher
Copernicus GmbH
Published
2017-07-18
Volume
8
Issue
3
Pages
577-616
ISSN
  • 2190-4979 (ISSN-L)
  • 2190-4987
DOI
10.5194/esd-8-577-2017
OpenAlex
W2522290956
Cited by
266
References
192
Citations by year
2026: 11 · 2025: 17 · 2024: 33 · 2023: 27 · 2022: 29 · 2021: 35 · 2020: 30 · 2019: 39 · 2018: 31 · 2017: 14
FWCI
21.61
Type
journal article
Language
en
Open access
Licence
Locations
  • Earth System Dynamics (publishedVersion, cc-by)
  • White Rose Research Online (University of Leeds, The University of Sheffield, University of York) (acceptedVersion)
  • ePrints Soton (University of Southampton) (acceptedVersion)
  • arXiv (Cornell University) (submittedVersion)
  • Aberdeen University Research Archive (Aberdeen University) (submittedVersion)
  • HAL (submittedVersion, other-oa)
  • DOAJ (DOAJ: Directory of Open Access Journals) (submittedVersion, cc-by-sa)
  • eScholarship (California Digital Library) (submittedVersion)
  • ANU Open Research (Australian National University) (submittedVersion)
  • arXiv (Cornell University)
Topics
  • Physical Sciences › Environmental Science › Global and Planetary Change › Climate variability and models
  • Social Sciences › Economics, Econometrics and Finance › Economics and Econometrics › Climate Change Policy and Economics
  • Physical Sciences › Environmental Science › Global and Planetary Change › Climate Change and Environmental Impact
Keywords
carbon dioxide removal, CO2 extraction, global warming, Eemian interglacial, sea level rise, energy balance, greenhouse gas forcing, fossil fuel emissions, climate change mitigation, youth, bioenergy with carbon capture and storage, air capture, reforestation, soil carbon

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