Skip to main content

Thank you for visiting nature.com. You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

Three decades of global methane sources and sinks

Abstract

Methane is an important greenhouse gas, responsible for about 20% of the warming induced by long-lived greenhouse gases since pre-industrial times. By reacting with hydroxyl radicals, methane reduces the oxidizing capacity of the atmosphere and generates ozone in the troposphere. Although most sources and sinks of methane have been identified, their relative contributions to atmospheric methane levels are highly uncertain. As such, the factors responsible for the observed stabilization of atmospheric methane levels in the early 2000s, and the renewed rise after 2006, remain unclear. Here, we construct decadal budgets for methane sources and sinks between 1980 and 2010, using a combination of atmospheric measurements and results from chemical transport models, ecosystem models, climate chemistry models and inventories of anthropogenic emissions. The resultant budgets suggest that data-driven approaches and ecosystem models overestimate total natural emissions. We build three contrasting emission scenarios — which differ in fossil fuel and microbial emissions — to explain the decadal variability in atmospheric methane levels detected, here and in previous studies, since 1985. Although uncertainties in emission trends do not allow definitive conclusions to be drawn, we show that the observed stabilization of methane levels between 1999 and 2006 can potentially be explained by decreasing-to-stable fossil fuel emissions, combined with stable-to-increasing microbial emissions. We show that a rise in natural wetland emissions and fossil fuel emissions probably accounts for the renewed increase in global methane levels after 2006, although the relative contribution of these two sources remains uncertain.

This is a preview of subscription content, access via your institution

Access options

Rent or buy this article

Prices vary by article type

from$1.95

to$39.95

Prices may be subject to local taxes which are calculated during checkout

Figure 1: Evolution of the atmospheric global mole fraction, growth rate and budget of methane for the past three decades.
Figure 2: Evolution of uncertainty on estimates of methane emissions and sinks presented in Table 1.
Figure 3: Regional budgets for 2000–2009 over 13 regions.
Figure 4: Plausible scenarios explaining changes in methane emissions over the past three decades.

Similar content being viewed by others

References

  1. Etheridge, D. M., Pearman, G. I. & Fraser, P. J. Changes in tropospheric methane between 1841 and 1978 from a high accumulation-rate Antarctic ice core. Tellus 44B, 282–294 (1992).

    Article  Google Scholar 

  2. Blake, D. R. et al. Global increase in atmospheric methane concentrations between 1978 and 1980. Geophys. Res. Lett. 9, 477–480 (1982).

    Article  Google Scholar 

  3. Cunnold, D. M. et al. In situ measurements of atmospheric methane at GAGE/AGAGE sites during 1985–2000 and resulting source inferences. J. Geophys. Res.: Atmos. http://dx.doi.org/10.1029/2001jd001226 (2002).

  4. Dlugokencky, E. J. et al. Observational constraints on recent increases in the atmospheric CH burden. Geophys. Res. Lett., 36, L18803 (2009).

    Article  Google Scholar 

  5. Francey, R. J., Steele, L. P., Langenfelds, R. L. & Pak, B. C. High precision long-term monitoring of radiatively active and related trace gases at surface sites and from aircraft in the southern hemisphere atmosphere. J. Atmos. Sci. 56, 279–285 (1999).

    Article  Google Scholar 

  6. World Data Centre for Greenhouse Gases (WMO/WDCGG) (2012); http://ds.data.jma.go.jp/gmd/wdcgg/introduction.html.

  7. Brenninkmeijer, C. A. M. et al. Civil Aircraft for the regular investigation of the atmosphere based on an instrumented container: The new CARIBIC system. Atmos. Chem. Phys. 7, 4953–4976 (2007).

    Article  Google Scholar 

  8. Wecht, K. J. et al. Validation of TES methane with HIPPO aircraft observations: implications for inverse modeling of methane sources. Atmos. Chem. Phys. 12, 1823–1832 (2012).

    Article  Google Scholar 

  9. Schuck, T. J. et al. Distribution of methane in the tropical upper troposphere measured by CARIBIC and CONTRAIL aircraft. J. Geophys. Res.: Atmos. 117, D19304 (2012).

    Article  Google Scholar 

  10. Crevoisier, C. et al. Tropospheric methane in the tropics — first year from IASI hyperspectral infrared observations. Atmos. Chem. Phys. 9, 6337–6350 (2009).

    Article  Google Scholar 

  11. Frankenberg, C. et al. Global column-averaged methane mixing ratios from 2003 to 2009 as derived from SCIAMACHY: Trends and variability. J. Geophys. Res.: Atmos. 116, D04302 (2011).

    Article  Google Scholar 

  12. Morino, I. et al. Preliminary validation of column-averaged volume mixing ratios of carbon dioxide and methane retrieved from GOSAT short-wavelength infrared spectra. Atmos. Meas. Tech. 4, 1061–1076 (2011).

    Article  Google Scholar 

  13. Dlugokencky, E. J., Nisbet, E. G., Fisher, R. & Lowry, D. Global atmospheric methane: budget, changes and dangers. Phil. Trans. R. Soc. A 369, 2058–2072 (2011).

    Article  Google Scholar 

  14. Rigby, M. et al. Renewed growth of atmospheric methane. Geophys. Res. Lett. 35, L22805 (2008).

    Article  Google Scholar 

  15. Simpson, I. J. et al. Long-term decline of global atmospheric ethane concentrations and implications for methane. Nature 488, 490–494 (2012).

    Article  Google Scholar 

  16. Denman, K. L. et al. in IPCC Climate Change 2007: Couplings Between Changes in the Climate System and Biogeochemistry (eds Solomon, S. et al.) (Cambridge Univ. Press; 2007).

    Google Scholar 

  17. Cicerone, R. J. & Oremland, R. S. Biogeochemical aspects of atmospheric methane. Glob. Biogeochem. Cycles 2, 299–327 (1988).

    Article  Google Scholar 

  18. Ehhalt, D. H. The atmospheric cycle of methane. Tellus 26, 58–70 (1974).

    Article  Google Scholar 

  19. Fung, I. et al. Three-dimensional model synthesis of global methane cycle. J. Geophys. Res. 96, 13033–13065 (1991).

    Article  Google Scholar 

  20. Monteil, G. et al. Interpreting methane variations in the past two decades using measurements of CH4 mixing ratio and isotopic composition. Atmos. Chem. Phys. 11, 9141–9153 (2011).

    Article  Google Scholar 

  21. Bousquet, P. et al. Contribution of anthropogenic and natural sources to atmospheric methane variability. Nature 443, 439–443 (2006).

    Article  Google Scholar 

  22. Neef, L., van Weele, M. & van Velthoven, P. Optimal estimation of the present-day global methane budget. Glob. Biogeochem. Cycles 24, GB4024 (2010).

    Article  Google Scholar 

  23. Wahlen, M., Tanaka, N., Henry, R. & Yoshinari, T. 13C, D and 14C in methane. Eos 68 1220 (1987).

    Google Scholar 

  24. Fisher, R. E. et al. Arctic methane sources: Isotopic evidence for atmospheric inputs. Geophys. Res. Lett. 38, L21803 (2011).

    Article  Google Scholar 

  25. Keppler, F., Hamilton, J. T. G., Brass, M. & Rockmann, T. Methane emissions from terrestrial plants under aerobic conditions. Nature 439, 187–191 (2006).

    Article  Google Scholar 

  26. Nisbet, R. E. R. et al. Emission of methane from plants. Proc. R. Soc. B-Biol. Sci. 276, 1347–1354 (2009).

    Article  Google Scholar 

  27. Curry, C. L. Modeling the soil consumption of atmospheric methane at the global scale. Glob. Biogeochem. Cycles 21, GB4012 (2007).

    Article  Google Scholar 

  28. Zhuang, Q. et al. Methane fluxes between terrestrial ecosystems and the atmosphere at northern high latitudes during the past century: A retrospective analysis with a process-based biogeochemistry model. Glob. Biogeochem. Cycles 18, GB3010 (2004).

    Article  Google Scholar 

  29. Allan, W., Struthers, H. & Lowe, D. C. Methane carbon isotope effects caused by atomic chlorine in the marine boundary layer: Global model results compared with Southern Hemisphere measurements. J. Geophys. Res.: Atmos. 112, D04306 (2007).

    Article  Google Scholar 

  30. Naik, V. et al. Preindustrial to present day changes in tropospheric hydroxyl radical and methane lifetime from the Atmospheric Chemistry and Climate Model Intercomparison Project (ACCMIP). Atmos. Chem. Phys. 13, 5277–5298 (2013).

    Article  Google Scholar 

  31. Bastviken, D., Tranvik, L. J., Downing, J. A., Crill, P. M. & Enrich-Prast, A. Freshwater methane emissions offset the continental carbon sink. Science 331, 50 (2011).

    Article  Google Scholar 

  32. Walter, K. M., Smith, L. C. & Stuart Chapin, F. Methane bubbling from northern lakes: present and future contributions to the global methane budget. Phil. Trans. R. Soc. A 365, 1657–1676 (2007).

    Article  Google Scholar 

  33. Huang, J. & Prinn, R. G. Critical evaluation of emissions of potential new gases for OH estimation. J. Geophys. Res. 107, 4784 (2002).

    Article  Google Scholar 

  34. Montzka, S. A. et al. Small interannual variability of global atmospheric hydroxyl. Science 331, 67–69 (2011).

    Article  Google Scholar 

  35. Etiope, G., Lassey, K. R., Klusman, R. W. & Boschi, E. Reappraisal of the fossil methane budget and related emission from geologic sources. Geophys. Res. Lett. 35, L09307 (2008).

    Article  Google Scholar 

  36. Shakhova, N. et al. Extensive methane venting to the atmosphere from sediments of the East Siberian Arctic Shelf. Science 327, 1246 (2010).

    Article  Google Scholar 

  37. Lassey, K. R., Lowe, D. C. & Smith, A. M. The atmospheric cycling of radiomethane and the “fossil fraction” of the methane source. Atmos. Chem. Phys. 7, 2141–2149 (2007).

    Article  Google Scholar 

  38. Voulgarakis, A. et al. Analysis of present day and future OH and methane lifetime in the ACCMIP simulations. Atmos. Chem. Phys. 13, 2563–2587 (2013).

    Article  Google Scholar 

  39. Melton, J. R. et al. Present state of global wetland extent and wetland methane modelling: conclusions from a model intercomparison project (WETCHIMP). Biogeosciences 10, 753–788 (2013).

    Article  Google Scholar 

  40. Hodson, E. L., Poulter, B., Zimmermann, N. E., Prigent, C. & Kaplan, J. O. The El Niño Southern Oscillation and wetland methane interannual variability. Geophys. Res. Lett. 38, L08810 (2011).

    Article  Google Scholar 

  41. Ringeval, B. et al. Climate-CH4 feedback from wetlands and its interaction with the climate-CO2 feedback. Biogeosciences 8, 2137–2157 (2011).

    Article  Google Scholar 

  42. Spahni, R. et al. Constraining global methane emissions and uptake by ecosystems. Biogeosciences 8, 1643–1665 (2011).

    Article  Google Scholar 

  43. Riley, W. J. et al. Barriers to predicting changes in global terrestrial methane fluxes: analyses using CLM4Me, a methane biogeochemistry model integrated in CESM. Biogeosciences 8, 1925–1953 (2011).

    Article  Google Scholar 

  44. Mastrandrea, M. D. et al. Guidance Note for Lead Authors of the IPCC Fifth Assessment Report on Consistent Treatment of Uncertainties (IPCC, 2010); http://www.ipcc.ch.

  45. Ohara, T. et al. An Asian emission inventory of anthropogenic emission sources for the period 1980–2020 Atmos Chem Phys 7, 4419–4444 (2007).

    Article  Google Scholar 

  46. Bergamaschi, P. et al. Inverse modeling of global and regional CH4 emissions using SCIAMACHY satellite retrievals. J. Geophys. Res. http://dx.doi.org/10.1029/2009JD012287 (2009).

  47. Van der Werf, G. R. et al. Global fire emissions and the contribution of deforestation, savanna, forest, agricultural, and peat fires (1997–2009). Atmos. Chem. Phys. 10, 11707–11735 (2010).

    Article  Google Scholar 

  48. Sanderson, M. G. Biomass of termites and their emissions of methane and carbon dioxide: A global database. Glob. Biogeochem. Cycles 10, 543–557 (1996).

    Article  Google Scholar 

  49. Bousquet, P., Hauglustaine, D. A., Peylin, P., Carouge, C. & Ciais, P. Two decades of OH variability as inferred by an inversion of atmospheric transport and chemistry of methyl chloroform. Atmos. Chem. Phys. 5, 2635–2656 (2005).

    Article  Google Scholar 

  50. Simpson, I. J., Rowland, F. S., Meinardi, S. & Blake, D. R. Influence of biomass burning during recent fluctuations in the slow growth of global tropospheric methane. Geophys. Res. Lett. 33, L22808 (2006).

    Article  Google Scholar 

  51. Dlugokencky, E. J. et al. Changes in CH4 and CO growth rates after the eruption of Mt Pinatubo and their link with changes in tropical tropospheric UV flux. Geophys. Res. Lett. 23, 2761–2764 (1996).

    Article  Google Scholar 

  52. Langenfelds, R. L. et al. Interannual growth rate variations of atmospheric CO2 and its delta 13C, H2, CH4, and CO between 1992 and 1999 linked to biomass burning. Glob. Biogeochem. Cycles 16, 1048 (2002).

    Article  Google Scholar 

  53. Bousquet, P. et al. Source attribution of the changes in atmospheric methane for 2006–2008 Atmos. Chem. Phys. 11, 3689–3700 (2011).

    Article  Google Scholar 

  54. Dlugokencky, E. J., Masarie, K. A., Lang, P. M. & Tans, P. P. Continuing decline in the growth rate of the atmospheric methane burden. Nature 393, 447–450 (1998).

    Article  Google Scholar 

  55. Environmental Protection Agency. Global Anthropogenic Non-CO2 Greenhouse Gas Emissions: 1990–2030. (US Environmental Protection Agency, 2011).

  56. European Commission, Joint Research Centre/Netherlands Environmental Assessment Agency. Emission Database for Global Atmospheric Research (EDGAR) (version 4.2) (2011); http://edgar.jrc.ec.europa.eu.

  57. Aydin, M. et al. Recent decreases in fossil-fuel emissions of ethane and methane derived from firn air. Nature 476, 198–201 (2011).

    Article  Google Scholar 

  58. Kai, F. M., Tyler, S. C., Randerson, J. T. & Blake, D. R. Reduced methane growth rate explained by decreased Northern Hemisphere microbial sources. Nature 476, 194–197 (2011).

    Article  Google Scholar 

  59. Levin, I. et al. No inter-hemispheric δ13CH4 trend observed. Nature 486, E3–E4 (2012).

    Article  Google Scholar 

  60. Bloom, A. A., Palmer, P. I., Fraser, A., Reay, D. S. & Frankenberg, C. Large-scale controls of methanogenesis inferred from methane and gravity spaceborne data. Science 327, 322–325 (2010).

    Article  Google Scholar 

  61. Prigent, C., Papa, F., Aires, F., Rossow, W. B. & Matthews, E. Global inundation dynamics inferred from multiple satellite observations, 1993–2000. J. Geophys. Res. 112, D12107 (2007).

    Article  Google Scholar 

  62. FLUXNET database; http://fluxnet.ornl.gov.

  63. Lewis, S. L., Brando, P. M., Phillips, O. L., van der Heijden, G. M. F. & Nepstad, D. The 2010 Amazon drought. Science 331, 554–554 (2011).

    Article  Google Scholar 

  64. Houweling, S. et al. Iconic CO2 Time Series at Risk. Science 337, 1038–1040 (2012).

    Article  Google Scholar 

  65. Lamarque, J. F. et al. The Atmospheric Chemistry and Climate Model Intercomparison Project (ACCMIP): overview and description of models, simulations and climate diagnostics. Geosci. Model Dev. 6, 179–206 (2013).

    Article  Google Scholar 

  66. Patra, P. K. et al. TransCom model simulations of CH4 and related species: linking transport, surface flux and chemical loss with CH4 variability in the troposphere and lower stratosphere. Atmos. Chem. Phys. 11, 12813–12837 (2011).

    Article  Google Scholar 

  67. Kiemle, C. et al. Sensitivity studies for a space-based methane lidar mission. Atmos. Meas. Tech. 4, 2195–2211 (2011).

    Article  Google Scholar 

  68. Shindell, D. et al. Simultaneously mitigating near-term climate change and improving human health and food security. Science 335, 183–189 (2012).

    Article  Google Scholar 

  69. Howarth, R., Santoro, R. & Ingraffea, A. Methane and the greenhouse-gas footprint of natural gas from shale formations. Climatic Change 106, 679–690 (2011).

    Article  Google Scholar 

  70. Cathles, L., Brown, L., Taam, M. & Hunter, A. A commentary on “The greenhouse-gas footprint of natural gas in shale formations” by R. W. Howarth, R. Santoro, and Anthony Ingraffea. Climatic Change 113, 525–535 (2012).

    Article  Google Scholar 

  71. Koven, C. D. et al. Permafrost carbon-climate feedbacks accelerate global warming. Proc. Natl Acad. Sci. USA 108, 14769–14774 (2011).

    Article  Google Scholar 

  72. Global Carbon Project (2013); http://www.globalcarbonproject.org/index.htm.

  73. Bruhwiler, L., Dlugokencky, E. J. & Masarie, K. AGU Fall Meeting abstr. B11G-01 (2011).

  74. Chen, Y. H. & Prinn, R. G. Estimation of atmospheric methane emissions between 1996 and 2001 using a three-dimensional global chemical transport model. J. Geophys. Res. 111, D10307 (2006).

    Google Scholar 

  75. Fraser, A. et al. Estimating regional methane surface fluxes: the relative importance of surface and GOSAT mole fraction measurements. Atmos. Chem. Phys. 13, 5697–5713 (2013).

    Article  Google Scholar 

  76. Hein, R., Crutzen, P. J. & Heimann, M. An inverse modeling approach to investigate the global atmospheric methane cycle. Glob. Biogeochem. Cycles 11, 43–76 (1997).

    Article  Google Scholar 

  77. Pison, I., Bousquet, P., Chevallier, F., Szopa, S. & Hauglustaine, D. Multi-species inversion of CH4, CO and H-2 emissions from surface measurements. Atmos. Chem. Phys. 9, 5281–5297 (2009).

    Article  Google Scholar 

  78. Mieville, A. et al. Emissions of gases and particles from biomass burning during the 20th century using satellite data and an historical reconstruction. Atmos. Environ. 44, 1469–1477 (2010).

    Article  Google Scholar 

  79. Van het Bolscher, M. et al. Emission data sets and methodologies for estimating emissions (eds Schultz, M. G. & Rast, S.) (2007).

  80. Wiedinmyer, C. et al. The Fire INventory from NCAR (FINN): a high resolution global model to estimate the emissions from open burning. Geosci. Model Dev. 4, 625–641 (2011).

    Article  Google Scholar 

  81. Dentener, F. et al. The impact of air pollutant and methane emission controls on tropospheric ozone and radiative forcing: CTM calculations for the period 1990–2030 Atmos. Chem. Phys. 5, 1731–1755 (2005).

    Article  Google Scholar 

  82. Environmental Protection Agency. Methane and Nitrous Oxide Emissions From Natural Sources. (US Environmental Protection Agency, 2010).

  83. Williams, J. E., Strunk, A., Huijnen, V. & van Weele, M. The application of the Modified Band Approach for the calculation of on-line photodissociation rate constants in TM5: implications for oxidative capacity. Geosci. Model Dev. 5, 15–35 (2012).

    Article  Google Scholar 

  84. Gurney, K. R. et al. Transcom 3 inversion intercomparison: Model mean results for the estimation of seasonal carbon sources and sinks. Glob. Biogeochem. Cycles 18, GB2010 (2004).

    Article  Google Scholar 

  85. Prinn, R. G. et al. Evidence for substantial variations of atmospheric hydroxyl radicals in the past two decades. Science 292, 1882–1888 (2001).

    Article  Google Scholar 

  86. Beck, V. et al. Methane airborne measurements and comparison to global models during BARCA. Journal of Geophysical Research: Atmospheres 117, D15310 (2012).

    Article  Google Scholar 

  87. Dickens, G. R. Methane hydrates in quaternary climate change — The clathrate gun hypothesis. Science 299, 1017–1017 (2003).

    Article  Google Scholar 

  88. Hoelzemann, J. J., Schultz, M. G., Brasseur, G. P., Granier, C. & Simon, M. Global Wildland Fire Emission Model (GWEM): Evaluating the use of global area burnt satellite data. J. Geophys. Res. 109, D14S04 (2004).

    Article  Google Scholar 

  89. Ito, A. & Penner, J. E. Global estimates of biomass burning emissions based on satellite imagery for the year 2000. J. Geophys. Res. 109, D14S05 (2004).

    Google Scholar 

  90. Rhee, T. S., Kettle, A. J. & Andreae, M. O. Methane and nitrous oxide emissions from the ocean: A reassessment using basin-wise observations in the Atlantic. J. Geophys. Res. 114, D12304 (2009).

    Article  Google Scholar 

  91. Sugimoto, A., Inoue, T., Kirtibutr, N. & Abe, T. Methane oxidation by termite mounds estimated by the carbon isotopic composition of methane. Glob. Biogeochem. Cycles 12, 595–605 (1998).

    Article  Google Scholar 

  92. Kasibhatla, K. et al. Inverse Methods in Global Biogeochemical Cycles, Volume 114 (AGU, 2000).

  93. Rodgers, C. D. Inverse Methods for Atmospheric Sounding: Theory and Practice (World Scientific, 2000).

    Book  Google Scholar 

  94. Krol, M. & Lelieveld, J. Can the variability in tropospheric OH be deduced from measurements of 1,1,1-trichloroethane (methyl chloroform)? J. Geophys. Res. 108, 4125 (2003).

    Article  Google Scholar 

Download references

Acknowledgements

This paper is the result of an international collaboration of scientists organized by the Global Carbon Project, a joint project of the Earth System Science Partnership. This work was supported by: the UK NERC National Centre for Earth Observation; the European Commission's 7th Framework Programme (FP7/2007-2013) projects MACC (grant agreement no. 218793) and GEOCARBON (grant agreement no. 283080); contract DE-AC52-07NA27344 with different parts supported by the US DOE IMPACTS and SciDAC Climate Consortium projects; computing resources of NERSC, which is supported by the US DOE under contract DE-AC02-05CH11231; NOAA flask data for CH3CCl3 (made available by S. Montzka); the Australian Climate Change Science Program, and ERC grant 247349. Simulations from LSCE were performed using HPC resources from DSM-CCRT and CCRT/CINES/IDRIS under the allocation 2012-t2012012201 made by GENCI (Grand Equipement National de Calcul Intensif). We thank the EDGAR group at JRC (Italy) and US-EPA for providing estimates of anthropogenic emissions.

Author information

Authors and Affiliations

Authors

Contributions

S.K., P. Bousquet, P.C., J.G.C. and C.L.Q. designed the study and provided conceptual advice. S.K., P. Bousquet and M. Saunois processed data sets, developed figures and wrote the manuscript. E.J.D., M. Schmidt, P.J.F., P.B.K., L.P.S., R.L.L., R.G.P., M.R., R.F.W., D.R.B. and I.J.S. provided atmospheric in situ data. P.Bousquet, P.Bergamaschi, L.B., F.C., L.F., A.F., S.H., P.I.P. and I.P. provided top-down inversion results (all five emission categories). S.C., E.L.H., B.P., B.R., M.Santini, R.S. and G.R.v.d.W provided bottom-up modelling and inventory data sets for wetland, biomass burning and termite emissions. D.B., P.C.-S., B.J., J.-F.L., V.N., D.P., D.T.S., S.A.S., K.S., S.S., A.V., M.v.W., J.E.W. and G.Z. provided bottom-up estimates of CH4 loss due to OH. All authors contributed extensively to the work presented in this paper, and to revisions of the manuscript.

Corresponding author

Correspondence to Philippe Bousquet.

Ethics declarations

Competing interests

The authors declare no competing financial interests.

Supplementary information

Supplementary Information

Supplementary Information (PDF 2701 kb)

Rights and permissions

Reprints and permissions

About this article

Cite this article

Kirschke, S., Bousquet, P., Ciais, P. et al. Three decades of global methane sources and sinks. Nature Geosci 6, 813–823 (2013). https://doi.org/10.1038/ngeo1955

Download citation

  • Received:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI: https://doi.org/10.1038/ngeo1955

This article is cited by

Search

Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing