Letter | Published:

Observational determination of surface radiative forcing by CO2 from 2000 to 2010

Nature volume 519, pages 339343 (19 March 2015) | Download Citation


The climatic impact of CO2 and other greenhouse gases is usually quantified in terms of radiative forcing1, calculated as the difference between estimates of the Earth’s radiation field from pre-industrial and present-day concentrations of these gases. Radiative transfer models calculate that the increase in CO2 since 1750 corresponds to a global annual-mean radiative forcing at the tropopause of 1.82 ± 0.19 W m−2 (ref. 2). However, despite widespread scientific discussion and modelling of the climate impacts of well-mixed greenhouse gases, there is little direct observational evidence of the radiative impact of increasing atmospheric CO2. Here we present observationally based evidence of clear-sky CO2 surface radiative forcing that is directly attributable to the increase, between 2000 and 2010, of 22 parts per million atmospheric CO2. The time series of this forcing at the two locations—the Southern Great Plains and the North Slope of Alaska—are derived from Atmospheric Emitted Radiance Interferometer spectra3 together with ancillary measurements and thoroughly corroborated radiative transfer calculations4. The time series both show statistically significant trends of 0.2 W m−2 per decade (with respective uncertainties of ±0.06 W m−2 per decade and ±0.07 W m−2 per decade) and have seasonal ranges of 0.1–0.2 W m−2. This is approximately ten per cent of the trend in downwelling longwave radiation5,6,7. These results confirm theoretical predictions of the atmospheric greenhouse effect due to anthropogenic emissions, and provide empirical evidence of how rising CO2 levels, mediated by temporal variations due to photosynthesis and respiration, are affecting the surface energy balance.

Access optionsAccess options

Rent or Buy article

Get time limited or full article access on ReadCube.


All prices are NET prices.


  1. 1.

    et al. in Climate Change 2001: The Scientific Basis. Contribution of Working Group I to the Third Assessment Report of the Intergovernmental Panel on Climate Change (eds et al.) 349–416 (Cambridge Univ. Press, 2001)

  2. 2.

    et al. 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 (eds et al.) 661 (Cambridge Univ. Press, 2013)

  3. 3.

    et al. Atmospheric emitted radiance interferometer. Part I: Instrument design. J. Atmos. Ocean. Technol. 21, 1763–1776 (2004)

  4. 4.

    et al. The continual intercomparison of radiation codes: results from phase I. J. Geophys. Res. 117, D06118 (2012)

  5. 5.

    The climatological record of clear-sky longwave radiation at the Earth's surface: evidence for water vapour feedback? Int. J. Remote Sens. 29, 5247–5263 (2008)

  6. 6.

    , & Combined surface solar brightening and increasing greenhouse effect support recent intensification of the global land-based hydrological cycle. Geophys. Res. Lett. 35, L17706 (2008)

  7. 7.

    & Global atmospheric downward longwave radiation over land surface under all-sky conditions from 1973 to 2008. J. Geophys. Res. 114, D19101 (2009)

  8. 8.

    , , & Increases in greenhouse forcing inferred from the outgoing longwave radiation spectra of the Earth in 1970 and 1997. Nature 410, 355–357 (2001)

  9. 9.

    , , & Climate change sensitivity evaluation from AIRS and IRIS measurements. Proc. SPIE 8153, XVI, (2011)

  10. 10.

    et al. The HITRAN2012 molecular spectroscopic database. J. Quant. Spectrosc. Radiat. 130, 4–50 (2013)

  11. 11.

    , , , & Influence of line mixing on absorption by CO2 Q branches in atmospheric balloon-borne spectra near 13 µm. J. Geophys. Res. 102 (D11). 12891–12899 (1997)

  12. 12.

    , & Spectra calculations in central and wing regions of CO2 IR bands. IV: Software and database for the computation of atmospheric spectra. J. Quant. Spectrosc. Radiat. 95, 469–481 (2005)

  13. 13.

    et al. Performance of the Line-By-Line Radiative Transfer Model (LBLRTM) for temperature, water vapor, and trace gas retrievals: recent updates evaluated with IASI case studies. Atmos. Chem. Phys. 13, 6687–6711 (2013)

  14. 14.

    et al. Radiative forcing by long-lived greenhouse gases: calculations with the AER radiative transfer models. J. Geophys. Res. 113, D13103 (2008)

  15. 15.

    et al. An update on Earth’s energy balance in light of the latest global observations. Nature Geosci. 5, 691–696 (2012)

  16. 16.

    & Thermal equilibrium of the atmosphere with a given distribution of relative humidity. J. Atmos. Sci. 24, 241–259 (1967)

  17. 17.

    & The Atmospheric Radiation Measurement (ARM) program: programmatic background and design of the cloud and radiation test bed. Bull. Am. Meteorol. Soc. 75, 1201–1221 (1994)

  18. 18.

    et al. Atmospheric radiative transfer modeling: a summary of the AER codes. J. Quant. Spectrosc. Radiat. 91, 233–244 (2005)

  19. 19.

    et al. Ground-based high spectral resolution observations of the entire terrestrial spectrum under extremely dry conditions. Geophys. Res. Lett. 39, L10801 (2012)

  20. 20.

    et al. An atmospheric perspective on North American carbon dioxide exchange: CarbonTracker. Proc. Natl Acad. Sci. USA 104, 18925–18930 (2007)

  21. 21.

    et al. CarbonTracker-CH4: an assimilation system for estimating emissions of atmospheric methane. Atmos. Chem. Phys. 14, 8269–8293 (2014)

  22. 22.

    et al. MERRA: NASA’s Modern-Era Retrospective Analysis for Research and Applications. J. Clim. 24, 3624–3648 (2011)

  23. 23.

    & Long-term trends in downwelling spectral infrared radiance over the U.S. Southern Great Plains. J. Clim. 24, 4831–4843 (2011)

  24. 24.

    et al. Objective determination of cloud heights and radar reflectivities using a combination of active remote sensors at the ARM CART sites. J. Appl. Meteorol. 39, 645–665 (2000)

  25. 25.

    et al. Factors affecting the detection of trends: statistical considerations and applications to environmental data. J. Geophys. Res. 103 (D14). 17149–17161 (1998)

  26. 26.

    , & A statistical method for testing a general circulation model with spectrally resolved satellite data. J. Geophys. Res. 102, 16563–16581 (1997)

  27. 27.

    et al. Separation of longwave climate feedbacks from spectral observations. J. Geophys. Res. 115, D07104 (2010)

  28. 28.

    , , & Anthropogenic greenhouse forcing and strong water vapor feedback increase temperature in Europe. Geophys. Res. Lett. 32, L19809 (2005)

  29. 29.

    et al. Water-vapor climate feedback inferred from climate fluctuations, 2003–2008. Geophys. Res. Lett. 35, L20704 (2008)

  30. 30.

    et al. The roles of aerosol, water vapor and cloud in future global dimming/brightening. J. Geophys. Res. 116, D20203 (2011)

  31. 31.

    et al. Traceability of absolute radiometric calibration for the Atmospheric Emitted Radiance Interferometer (AERI). In Conf. on Characterization and Radiometric Calibration for Remote Sensing (Space Dynamics Laboratory, Utah State Univ.. , 15–18 Sept) (2003)

  32. 32.

    et al. Atmospheric Emitted Radiance Interferometer. Part II: Instrument performance. J. Atmos. Ocean. Technol. 21, 1777–1789 (2004)

  33. 33.

    et al. Impact of CO2 measurement bias on CarbonTracker surface flux estimates. J. Geophys. Res. 116, D17305 (2011)

  34. 34.

    , , , & Measurements of carbon dioxide on a very tall tower. Tellus B. 47, 535–549 (1995)

  35. 35.

    , , & Measurements of carbon dioxide on very tall towers: results of the NOAA/CMDL program. Tellus B. 50, 401–415 (1998)

  36. 36.

    et al. A multi-year record of airborne CO2 observations in the US Southern Great Plains. Atmos. Meas. Technol. 6, 751–763 (2013)

  37. 37.

    et al. Corrections of humidity measurement errors from the Vaisala RS80 radiosonde—application to TOGA COARE data. J. Atmos. Ocean. Technol. 19, 981–1002 (2002)

  38. 38.

    in Microwave Radiometry and Remote Sensing of the Earth’s Surface and Atmosphere (eds & ) 433–443 (VSP Press, 1999)

  39. 39.

    , , & Accuracy of ground-based microwave radiometer and balloon-borne measurements during the WVIOP2000 field experiment. IEEE Trans. Geosci. Rem. Sens. 41, 2605–2615 (2003)

  40. 40.

    et al. The ARM Millimeter Wave Cloud Radars (MMCRs) and the Active Remote Sensing of Clouds (ARSCL) Value Added Product (VAP) DOE Tech. Memo. ARM VAP-002.1, (US Department of Energy, 2001)

  41. 41.

    Gaussian quadrature and its application to infrared radiation. J. Atmos. Sci. 57, 753–765 (2000)

  42. 42.

    et al. The broadband heating rate profile (BBHRP) VAP. Proc. 12th ARM Sci. Team Meet. ARM-CONF-2002 (US Department of Energy, 2002)

  43. 43.

    , & Radiatively Important Parameters Best Estimate (RIPBE): an ARM value-added product. DOE Tech. Rep. SC-ARM/TR-097 (US Department of Energy, 2011)

  44. 44.

    , , , & Precipitation, radiative forcing and global temperature change. Geophys. Res. Lett. 37, L14701 (2010)

  45. 45.

    et al. Radiative forcing by well-mixed greenhouse gases: estimates from climate models in the Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report (AR4). J. Geophys. Res. 111, D14317 (2006)

  46. 46.

    et al. AFGL atmospheric constituent profiles (0–120 km). AFGL-TR_86-0110, (Hanscom Air Force Base, Air Force Geophysics Laboratory, 1986)

Download references


This material is based upon work supported by the US Department of Energy, Office of Science, Office of Biological and Environmental Research, Climate and Environmental Science Division, of the US Department of Energy under Award Number DE-AC02-05CH11231 as part of the Atmospheric System Research Program and the Atmospheric Radiation Measurement (ARM) Climate Research Facility Southern Great Plains. We used resources of the National Energy Research Scientific Computing Center (NERSC) under that same award. I. Williams, W. Riley, and S. Biraud of the Lawrence Berkeley National Laboratory, and D. Turner of the National Severe Storms Laboratory also provided feedback. The Broadband Heating Rate Profile (BBHRP) runs were performed using Pacific Northwest National Laboratory (PNNL) Institutional Computing at PNNL, with help from K. Cady-Pereira of Atmospheric Environmental Research, Inc., L. Riihimaki of PNNL, and D. Troyan of Brookhaven National Laboratory.

Author information


  1. Lawrence Berkeley National Laboratory, Earth Sciences Division, 1 Cyclotron Road, MS 74R-316C, Berkeley, California 94720, USA

    • D. R. Feldman
    • , W. D. Collins
    •  & M. S. Torn
  2. University of California-Berkeley, Department of Earth and Planetary Science, 307 McCone Hall, MC 4767, Berkeley, California 94720, USA

    • W. D. Collins
  3. University of Wisconsin-Madison, Space Science and Engineering Center, 1225 W. Dayton Street, Madison, Wisconsin 53706, USA

    • P. J. Gero
  4. University of California-Berkeley, Energy and Resources Group, Berkeley, 310 Barrows Hall, MC 3050, California 94720, USA

    • M. S. Torn
  5. Atmospheric and Environmental Research, Inc., 131 Hartwell Avenue, Lexington, Massachusetts 02141, USA

    • E. J. Mlawer
  6. Pacific Northwest National Laboratory, Fundamental and Computational Sciences, 902 Battelle Boulevard, Richland, Washington 99354, USA

    • T. R. Shippert


  1. Search for D. R. Feldman in:

  2. Search for W. D. Collins in:

  3. Search for P. J. Gero in:

  4. Search for M. S. Torn in:

  5. Search for E. J. Mlawer in:

  6. Search for T. R. Shippert in:


D.R.F. implemented the study design, performed the analysis of all measurements from the ARM sites, and wrote the manuscript. W.D.C. proposed the study design and oversaw its implementation. P.J.G. is the AERI instrument mentor and ensured the proper use of spectral measurements and quality control. M.S.T. mentored the implementation of the study and oversaw its funding. E.J.M. and T.R.S. performed calculations and analysis to determine fair-weather bias. All authors discussed the results and commented on and edited the manuscript.

Competing interests

The authors declare no competing financial interests.

Corresponding author

Correspondence to D. R. Feldman.

Extended data

About this article

Publication history






Further reading Further reading


By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.