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Journal Article•DOI•

Impact of changes in diffuse radiation on the global land carbon sink

Lina M. Mercado, Nicolas Bellouin1, Stephen Sitch1, Olivier Boucher1, Chris Huntingford, Martin Wild2, Peter M. Cox3 •
Met Office1, ETH Zurich2, University of Exeter3
23 Apr 2009-Nature (Nature Publishing Group)-Vol. 458, Iss: 7241, pp 1014-1017
TL;DR: The authors used the HadGEM2-A general circulation model to simulate the effect of late twentieth century "global dimming" and associated increases in the diffuse radiation fraction on global carbon storage.
Abstract: Increased exposure to solar radiation generally increases plant photosynthesis, but not all forms of radiation are equally effective. In particular, field studies have demonstrated that a given amount of diffuse radiation leads to more fixed carbon than direct radiation. Mercado et al. use the HadGEM2-A general circulation model to simulate the effect of late twentieth century 'global dimming' and associated increases in the diffuse radiation fraction on global carbon storage. They find that increases in diffuse radiation enhanced the terrestrial carbon sink by about 25%. Paradoxically, reducing anthropogenic pollution in the future would reduce this diffuse radiation effect, thereby creating a positive feedback to global warming. More radiation generally increases vegetation photosynthesis, but field studies show that a given amount of diffuse radiation leads to more fixed carbon than direct radiation. Mercado and colleagues simulate the effect of late twentieth century increases in the diffuse radiation fraction, and find that the terrestrial carbon sink is enhanced by about 25% —paradoxically, reducing future anthropogenic pollution will reduce this diffuse radiation effect, creating a positive feedback to global warming. Plant photosynthesis tends to increase with irradiance. However, recent theoretical and observational studies have demonstrated that photosynthesis is also more efficient under diffuse light conditions1,2,3,4,5. Changes in cloud cover or atmospheric aerosol loadings, arising from either volcanic or anthropogenic emissions, alter both the total photosynthetically active radiation reaching the surface and the fraction of this radiation that is diffuse, with uncertain overall effects on global plant productivity and the land carbon sink. Here we estimate the impact of variations in diffuse fraction on the land carbon sink using a global model modified to account for the effects of variations in both direct and diffuse radiation on canopy photosynthesis. We estimate that variations in diffuse fraction, associated largely with the ‘global dimming’ period6,7,8, enhanced the land carbon sink by approximately one-quarter between 1960 and 1999. However, under a climate mitigation scenario for the twenty-first century in which sulphate aerosols decline before atmospheric CO2 is stabilized, this ‘diffuse-radiation’ fertilization effect declines rapidly to near zero by the end of the twenty-first century.

Summary (1 min read)

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Summary

  • Plant photosynthesis tends to increase with irradiance.
  • Recent theoretical and observational studies have demonstrated that photosynthesis is also more efficient under diffuse light conditions 1-5 .
  • Changes in cloud cover or atmospheric aerosol loadings, arising from either volcanic or anthropogenic emissions, alter both the total Photosynthetically Active Radiation (PAR) reaching the surface and the fraction of this radiation which is diffuse, with uncertain overall effects on global plant productivity and the land carbon sink.
  • Here the authors estimate for the first time, the impact of variations in diffuse fraction on the land carbon sink using a global model modified to account for the effects of variations in both direct and diffuse radiation on canopy photosynthesis.
  • The authors estimate that variations in diffuse fraction, associated largely with the "global dimming" period 6-8 , enhanced the land carbon sink by approximately a quarter.

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Impact of changes in diffuse radiation on
the global land carbon sink
Article
Accepted Version
Mercado, L. M., Bellouin, N., Sitch, S., Boucher, O.,
Huntingford, C., Wild, M. and Cox, P. M. (2009) Impact of
changes in diffuse radiation on the global land carbon sink.
Nature, 458 (7241). pp. 1014-1017. ISSN 0028-0836 doi:
https://doi.org/10.1038/nature07949 Available at
https://centaur.reading.ac.uk/30576/
It is advisable to refer to the publisher’s version if you intend to cite from the
work. See Guidance on citing
.
To link to this article DOI: http://dx.doi.org/10.1038/nature07949
Publisher: Nature Publishing Group
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including copyright law. Copyright and IPR is retained by the creators or other
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Reading’s research outputs online
Impact of Changes in Diffuse Radiation on the Global Land
Carbon Sink
Lina M. Mercado
1
, Nicolas Bellouin
2
, Stephen Sitch
2
, Olivier Boucher
2
, Chris
Huntingford
1
, Martin Wild
3
and Peter M. Cox
4
1
Centre for Ecology and Hydrology, Wallingford, Oxon OX10 8BB, UK
2
Met Office Hadley Centre, Exeter, EX1 3PB, UK
3
ETH Zurich, Institute for Atmospheric and Climate Science , CH 8092 Zurich,
Switzerland
4
School of Engineering, Computer Science and Mathematics, University of Exeter,
EX4 4QF, UK
Plant photosynthesis tends to increase with irradiance. However, recent
theoretical and observational studies have demonstrated that photosynthesis is
also more efficient under diffuse light conditions
1-5
. Changes in cloud cover or
atmospheric aerosol loadings, arising from either volcanic or anthropogenic
emissions, alter both the total Photosynthetically Active Radiation (PAR)
reaching the surface and the fraction of this radiation which is diffuse, with
uncertain overall effects on global plant productivity and the land carbon sink.
Here we estimate for the first time, the impact of variations in diffuse fraction on
the land carbon sink using a global model modified to account for the effects of
variations in both direct and diffuse radiation on canopy photosynthesis. We
estimate that variations in diffuse fraction, associated largely with the “global
dimming” period
6-8
, enhanced the land carbon sink by approximately a quarter
from 1960 to 1999. However, under a climate mitigation scenario for the 21
st
century in which sulphate aerosols decline before atmospheric CO
2
is stabilised,
this “diffuse-radiation” fertilisation effect declines rapidly to near zero by the
end of the 21
st
century.
The solar radiation reaching the Earth’s surface is the primary driver of plant photosynthesis.
Leaf photosynthesis increases non-linearly with incident PAR, saturating at light levels which
are often exceeded on bright days during the growing season (Fig 1). In clear-sky conditions, a
fraction of the plant canopy is illuminated by direct solar radiation consisting of bright
“sunflecks”, with the remaining portion of the canopy being in the shade. The sunlit fraction of
the canopy has leaves which are often light saturated and therefore have low light use
efficiency, while leaves in the shade are more light-use efficient but suffer from a lower
exposure to incoming radiation. In contrast, under cloudy or sulphate-aerosol-laden skies,
sunlight is more scattered and incoming radiation is more diffuse producing a more uniform
irradiance of the canopy with a smaller fraction of the canopy likely to be light-saturated. As a
result, canopy photosynthesis tends to be significantly more light-use efficient under diffuse
rather than direct sunlight
3
. Hence, the net effect on photosynthesis of radiation changes
associated with an increase in clouds or scattering aerosols depends on a balance between the
reduction in the overall total PAR (which tends to reduce photosynthesis) and the increase in
the diffuse fraction of the PAR (which tends to increase photosynthesis). While some global
climate-carbon cycle models include the effects of atmospheric aerosols on total irradiance and
surface temperature (e.g. ref. 9), none has accounted for the effects of clouds and aerosols on
the land carbon sink via changes in the diffuse fraction of radiation.
To account for the effects of diffuse radiation on canopy photosynthesis, we modified the
JULES land surface scheme used in the Hadley Centre climate models
10
. JULES includes a
multilayer approach to scale photosynthesis from the leaf to the canopy. In this study we also
separated each canopy layer into sunlit and shaded regions
11
. Figure 1 shows a comparison of
the simulated light response of Gross Primary Productivity (GPP) against measurements
inferred from the eddy correlation technique under direct and diffuse irradiance conditions
within a broadleaf
12
and a needleleaf temperate forest
13
. The modified JULES model is able to
reproduce the different light response curves under diffuse and direct radiation within the error
bars of the observations. A sensitivity analysis carried out for the broadleaf forest shows that
simulated GPP reaches a maximum at a diffuse fraction of 0.4 after which GPP decreases due
to a reduction in the total PAR (Fig S1).The existence of such an optimum is in agreement with
a previous modelling study for the same site
14
.
We performed multiple global simulations with JULES over the period 1901 to 2100 to assess
the impact of changing diffuse radiation on the global land carbon sink. For 1901 to 1999, we
used an observed monthly climatology of the main climate variables
15
, except direct and
diffuse total shortwave and PAR fluxes which were reconstructed using radiative transfer
calculations. The reconstruction takes into account the scattering and absorption of solar
radiation by tropospheric aerosols as simulated by the Hadley Centre Global Environmental
Model (version HadGEM2-A)
16
, a climatology of stratospheric aerosols
17
and a cloudiness
dataset
15
(see methodology). For the period 2000 to 2100 we prescribed varying atmospheric
CO
2
concentration and monthly fields of anthropogenic aerosols, following an A1B 450 ppm
CO
2
equivalent stabilization scenario relying on the A1B storyline and the methodology from
ref. 18. Under this scenario, diffuse fraction increases during the second half of the 20
th
century
and then decreases during the 21
st
century due to correspondingly increasing and decreasing
Citations
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Book Chapter•DOI•
Anthropogenic and Natural Radiative Forcing

[...]

Gunnar Myhre, Drew Shindell, Julia Pongratz
01 Jan 2014
TL;DR: Myhre et al. as discussed by the authors presented the contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC) 2013: Anthropogenic and Natural Radiative forcing.
Abstract: This chapter should be cited as: Myhre, G., D. Shindell, F.-M. Bréon, W. Collins, J. Fuglestvedt, J. Huang, D. Koch, J.-F. Lamarque, D. Lee, B. Mendoza, T. Nakajima, A. Robock, G. Stephens, T. Takemura and H. Zhang, 2013: Anthropogenic and Natural Radiative Forcing. In: Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change [Stocker, T.F., D. Qin, G.-K. Plattner, M. Tignor, S.K. Allen, J. Boschung, A. Nauels, Y. Xia, V. Bex and P.M. Midgley (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA. Coordinating Lead Authors: Gunnar Myhre (Norway), Drew Shindell (USA)

3,684 citations

Journal Article•DOI•
Terrestrial Gross Carbon Dioxide Uptake: Global Distribution and Covariation with Climate

[...]

Christian Beer1, Markus Reichstein1, Enrico Tomelleri1, Philippe Ciais2, Martin Jung1, Nuno Carvalhais1, Christian Rödenbeck1, M. Altaf Arain3, Dennis D. Baldocchi4, Gordon B. Bonan5, Alberte Bondeau6, Alessandro Cescatti, Gitta Lasslop1, Anders Lindroth7, Mark R. Lomas8, Sebastiaan Luyssaert9, Hank A. Margolis10, Keith W. Oleson5, Olivier Roupsard11, Elmar Veenendaal12, Nicolas Viovy2, Christopher M. Williams13, F. Ian Woodward8, Dario Papale •
Max Planck Society1, Centre national de la recherche scientifique2, McMaster University3, University of California, Berkeley4, National Center for Atmospheric Research5, Potsdam Institute for Climate Impact Research6, Lund University7, University of Sheffield8, University of Antwerp9, Laval University10, Centro Agronómico Tropical de Investigación y Enseñanza11, Wageningen University and Research Centre12, Clark University13
13 Aug 2010-Science
TL;DR: Estimates of spatially distributed GPP and its covariation with climate can help improve coupled climate–carbon cycle process models.
Abstract: Terrestrial gross primary production (GPP) is the largest global CO(2) flux driving several ecosystem functions. We provide an observation-based estimate of this flux at 123 +/- 8 petagrams of carbon per year (Pg C year(-1)) using eddy covariance flux data and various diagnostic models. Tropical forests and savannahs account for 60%. GPP over 40% of the vegetated land is associated with precipitation. State-of-the-art process-oriented biosphere models used for climate predictions exhibit a large between-model variation of GPP's latitudinal patterns and show higher spatial correlations between GPP and precipitation, suggesting the existence of missing processes or feedback mechanisms which attenuate the vegetation response to climate. Our estimates of spatially distributed GPP and its covariation with climate can help improve coupled climate-carbon cycle process models.

2,081 citations

Book Chapter•DOI•
Carbon and Other Biogeochemical Cycles

[...]

Philippe Ciais, Christopher L. Sabine, Govindasamy Bala, Laurent Bopp, Victor Brovkin1, Josep G. Canadell, Abha Chhabra2, Ruth DeFries, James N. Galloway, Martin Heimann1, Chris D. Jones, C. Le Quéré, Ranga B. Myneni, S. L. Piao, Peter E. Thornton •
Max Planck Society1, University of Bristol2
01 Jan 2014
TL;DR: For base year 2010, anthropogenic activities created ~210 (190 to 230) TgN of reactive nitrogen Nr from N2 as discussed by the authors, which is at least 2 times larger than the rate of natural terrestrial creation of ~58 Tg N (50 to 100 Tg nr yr−1) (Table 6.9, Section 1a).
Abstract: For base year 2010, anthropogenic activities created ~210 (190 to 230) TgN of reactive nitrogen Nr from N2. This human-caused creation of reactive nitrogen in 2010 is at least 2 times larger than the rate of natural terrestrial creation of ~58 TgN (50 to 100 TgN yr−1) (Table 6.9, Section 1a). Note that the estimate of natural terrestrial biological fixation (58 TgN yr−1) is lower than former estimates (100 TgN yr−1, Galloway et al., 2004), but the ranges overlap, 50 to 100 TgN yr−1 vs. 90 to 120 TgN yr−1, respectively). Of this created reactive nitrogen, NOx and NH3 emissions from anthropogenic sources are about fourfold greater than natural emissions (Table 6.9, Section 1b). A greater portion of the NH3 emissions is deposited to the continents rather than to the oceans, relative to the deposition of NOy, due to the longer atmospheric residence time of the latter. These deposition estimates are lower limits, as they do not include organic nitrogen species. New model and measurement information (Kanakidou et al., 2012) suggests that incomplete inclusion of emissions and atmospheric chemistry of reduced and oxidized organic nitrogen components in current models may lead to systematic underestimates of total global reactive nitrogen deposition by up to 35% (Table 6.9, Section 1c). Discharge of reactive nitrogen to the coastal oceans is ~45 TgN yr−1 (Table 6.9, Section 1d). Denitrification converts Nr back to atmospheric N2. The current estimate for the production of atmospheric N2 is 110 TgN yr−1 (Bouwman et al., 2013).

1,967 citations

Journal Article•DOI•
Trends in the sources and sinks of carbon dioxide

[...]

Corinne Le Quéré1, Corinne Le Quéré2, Michael R. Raupach3, Josep G. Canadell3, Gregg Marland4, Laurent Bopp5, Philippe Ciais5, Thomas J. Conway6, Scott C. Doney7, Richard A. Feely8, Pru N Foster9, Pierre Friedlingstein9, Kevin R. Gurney10, Richard A. Houghton7, Joanna Isobel House9, Chris Huntingford, Peter Levy, Mark R. Lomas11, Joseph D. Majkut12, Nicolas Metzl13, Jean Pierre Henry Balbaud Ometto14, Glen P. Peters15, I. Colin Prentice9, James T. Randerson16, Steven W. Running17, Jorge L. Sarmiento12, Ute Schuster2, Stephen Sitch18, Taro Takahashi19, Nicolas Viovy5, Guido R. van der Werf20, F. Ian Woodward11 •
British Antarctic Survey1, University of East Anglia2, Commonwealth Scientific and Industrial Research Organisation3, Oak Ridge National Laboratory4, Centre national de la recherche scientifique5, National Oceanic and Atmospheric Administration6, Woods Hole Oceanographic Institution7, Pacific Marine Environmental Laboratory8, University of Bristol9, Purdue University10, University of Sheffield11, Princeton University12, Pierre-and-Marie-Curie University13, National Institute for Space Research14, University of Oslo15, University of California, Irvine16, University of Montana17, University of Leeds18, Columbia University19, VU University Amsterdam20
01 Dec 2009-Nature Geoscience
TL;DR: In the past 50 years, the fraction of CO2 emissions that remains in the atmosphere each year has likely increased, from about 40% to 45%, and models suggest that this trend was caused by a decrease in the uptake of CO 2 by the carbon sinks in response to climate change and variability as mentioned in this paper.
Abstract: Efforts to control climate change require the stabilization of atmospheric CO2 concentrations. This can only be achieved through a drastic reduction of global CO2 emissions. Yet fossil fuel emissions increased by 29% between 2000 and 2008, in conjunction with increased contributions from emerging economies, from the production and international trade of goods and services, and from the use of coal as a fuel source. In contrast, emissions from land-use changes were nearly constant. Between 1959 and 2008, 43% of each year's CO2 emissions remained in the atmosphere on average; the rest was absorbed by carbon sinks on land and in the oceans. In the past 50 years, the fraction of CO2 emissions that remains in the atmosphere each year has likely increased, from about 40% to 45%, and models suggest that this trend was caused by a decrease in the uptake of CO2 by the carbon sinks in response to climate change and variability. Changes in the CO2 sinks are highly uncertain, but they could have a significant influence on future atmospheric CO2 levels. It is therefore crucial to reduce the uncertainties.

1,909 citations

Journal Article•DOI•
Global Carbon Budget 2020

[...]

Pierre Friedlingstein1, Pierre Friedlingstein2, Michael O'Sullivan1, Matthew W. Jones3, Robbie M. Andrew, Judith Hauck, Are Olsen, Glen P. Peters, Wouter Peters4, Wouter Peters5, Julia Pongratz6, Julia Pongratz7, Stephen Sitch2, Corinne Le Quéré3, Josep G. Canadell8, Philippe Ciais9, Robert B. Jackson10, Simone R. Alin11, Luiz E. O. C. Aragão12, Luiz E. O. C. Aragão2, Almut Arneth, Vivek K. Arora, Nicholas R. Bates13, Nicholas R. Bates14, Meike Becker, Alice Benoit-Cattin, Henry C. Bittig, Laurent Bopp15, Selma Bultan6, Naveen Chandra16, Naveen Chandra17, Frédéric Chevallier9, Louise Chini18, Wiley Evans, Liesbeth Florentie5, Piers M. Forster19, Thomas Gasser20, Marion Gehlen9, Dennis Gilfillan, Thanos Gkritzalis21, Luke Gregor22, Nicolas Gruber22, Ian Harris23, Kerstin Hartung24, Kerstin Hartung6, Vanessa Haverd8, Richard A. Houghton25, Tatiana Ilyina7, Atul K. Jain26, Emilie Joetzjer27, Koji Kadono28, Etsushi Kato, Vassilis Kitidis29, Jan Ivar Korsbakken, Peter Landschützer7, Nathalie Lefèvre30, Andrew Lenton31, Sebastian Lienert32, Zhu Liu33, Danica Lombardozzi34, Gregg Marland35, Nicolas Metzl30, David R. Munro11, David R. Munro36, Julia E. M. S. Nabel7, S. Nakaoka17, Yosuke Niwa17, Kevin D. O'Brien37, Kevin D. O'Brien11, Tsuneo Ono, Paul I. Palmer, Denis Pierrot38, Benjamin Poulter, Laure Resplandy39, Eddy Robertson40, Christian Rödenbeck7, Jörg Schwinger, Roland Séférian27, Ingunn Skjelvan, Adam J. P. Smith3, Adrienne J. Sutton11, Toste Tanhua41, Pieter P. Tans11, Hanqin Tian42, Bronte Tilbrook31, Bronte Tilbrook43, Guido R. van der Werf44, N. Vuichard9, Anthony P. Walker45, Rik Wanninkhof38, Andrew J. Watson2, David R. Willis23, Andy Wiltshire40, Wenping Yuan46, Xu Yue47, Sönke Zaehle7 •
École Normale Supérieure1, University of Exeter2, Norwich Research Park3, University of Groningen4, Wageningen University and Research Centre5, Ludwig Maximilian University of Munich6, Max Planck Society7, Commonwealth Scientific and Industrial Research Organisation8, Université Paris-Saclay9, Stanford University10, National Oceanic and Atmospheric Administration11, National Institute for Space Research12, University of Southampton13, Bermuda Institute of Ocean Sciences14, PSL Research University15, Japan Agency for Marine-Earth Science and Technology16, National Institute for Environmental Studies17, University of Maryland, College Park18, University of Leeds19, International Institute of Minnesota20, Flanders Marine Institute21, ETH Zurich22, University of East Anglia23, German Aerospace Center24, Woods Hole Research Center25, University of Illinois at Urbana–Champaign26, University of Toulouse27, Japan Meteorological Agency28, Plymouth Marine Laboratory29, University of Paris30, Hobart Corporation31, Oeschger Centre for Climate Change Research32, Tsinghua University33, National Center for Atmospheric Research34, Appalachian State University35, University of Colorado Boulder36, University of Washington37, Atlantic Oceanographic and Meteorological Laboratory38, Princeton University39, Met Office40, Leibniz Institute of Marine Sciences41, Auburn University42, University of Tasmania43, VU University Amsterdam44, Oak Ridge National Laboratory45, Sun Yat-sen University46, Nanjing University47
11 Dec 2020-Earth System Science Data
TL;DR: In this paper, the authors describe and synthesize data sets and methodology to quantify the five major components of the global carbon budget and their uncertainties, including emissions from land use and land-use change data and bookkeeping models.
Abstract: Accurate assessment of anthropogenic carbon dioxide (CO2) emissions and their redistribution among the atmosphere, ocean, and terrestrial biosphere in a changing climate – the “global carbon budget” – is important to better understand the global carbon cycle, support the development of climate policies, and project future climate change. Here we describe and synthesize data sets and methodology to quantify the five major components of the global carbon budget and their uncertainties. Fossil CO2 emissions (EFOS) are based on energy statistics and cement production data, while emissions from land-use change (ELUC), mainly deforestation, are based on land use and land-use change data and bookkeeping models. Atmospheric CO2 concentration is measured directly and its growth rate (GATM) is computed from the annual changes in concentration. The ocean CO2 sink (SOCEAN) and terrestrial CO2 sink (SLAND) are estimated with global process models constrained by observations. The resulting carbon budget imbalance (BIM), the difference between the estimated total emissions and the estimated changes in the atmosphere, ocean, and terrestrial biosphere, is a measure of imperfect data and understanding of the contemporary carbon cycle. All uncertainties are reported as ±1σ. For the last decade available (2010–2019), EFOS was 9.6 ± 0.5 GtC yr−1 excluding the cement carbonation sink (9.4 ± 0.5 GtC yr−1 when the cement carbonation sink is included), and ELUC was 1.6 ± 0.7 GtC yr−1. For the same decade, GATM was 5.1 ± 0.02 GtC yr−1 (2.4 ± 0.01 ppm yr−1), SOCEAN 2.5 ± 0.6 GtC yr−1, and SLAND 3.4 ± 0.9 GtC yr−1, with a budget imbalance BIM of −0.1 GtC yr−1 indicating a near balance between estimated sources and sinks over the last decade. For the year 2019 alone, the growth in EFOS was only about 0.1 % with fossil emissions increasing to 9.9 ± 0.5 GtC yr−1 excluding the cement carbonation sink (9.7 ± 0.5 GtC yr−1 when cement carbonation sink is included), and ELUC was 1.8 ± 0.7 GtC yr−1, for total anthropogenic CO2 emissions of 11.5 ± 0.9 GtC yr−1 (42.2 ± 3.3 GtCO2). Also for 2019, GATM was 5.4 ± 0.2 GtC yr−1 (2.5 ± 0.1 ppm yr−1), SOCEAN was 2.6 ± 0.6 GtC yr−1, and SLAND was 3.1 ± 1.2 GtC yr−1, with a BIM of 0.3 GtC. The global atmospheric CO2 concentration reached 409.85 ± 0.1 ppm averaged over 2019. Preliminary data for 2020, accounting for the COVID-19-induced changes in emissions, suggest a decrease in EFOS relative to 2019 of about −7 % (median estimate) based on individual estimates from four studies of −6 %, −7 %, −7 % (−3 % to −11 %), and −13 %. Overall, the mean and trend in the components of the global carbon budget are consistently estimated over the period 1959–2019, but discrepancies of up to 1 GtC yr−1 persist for the representation of semi-decadal variability in CO2 fluxes. Comparison of estimates from diverse approaches and observations shows (1) no consensus in the mean and trend in land-use change emissions over the last decade, (2) a persistent low agreement between the different methods on the magnitude of the land CO2 flux in the northern extra-tropics, and (3) an apparent discrepancy between the different methods for the ocean sink outside the tropics, particularly in the Southern Ocean. This living data update documents changes in the methods and data sets used in this new global carbon budget and the progress in understanding of the global carbon cycle compared with previous publications of this data set (Friedlingstein et al., 2019; Le Quere et al., 2018b, a, 2016, 2015b, a, 2014, 2013). The data presented in this work are available at https://doi.org/10.18160/gcp-2020 (Friedlingstein et al., 2020).

1,764 citations

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1,253 citations

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