Papers on changes in OLR due to GHG’s
Posted by Ari Jokimäki on August 2, 2009
This list of papers contains evidence of changes in outgoing longwave radiation (OLR) caused by changing concentrations of greenhouse gases (GHG). The list is not complete, and will most likely be updated in the future in order to make it more thorough and more representative.
UPDATE (July 3, 2016): Brindley & Bantges (2016) added.
UPDATE (April 3, 2014): Gastineau et al. (2014) added.
UPDATE (July 10, 2013): Chapman et al. (2013) added.
UPDATE (June 28, 2012): Chédin et al. (2003), Strow et al. (2006), Buchwitz et al. (2007), and Strow & Hannon (2008) removed. Most of these papers are now found in the list of atmospheric carbon dioxide measurements.
UPDATE (June 26, 2012): Papers divided to observations and theories & models. Harries et al. (1995), Brindley & Allan (2003), Huang & Ramaswamy (2009), Huang et al. (2010) and Huang et al. (2010) added.
UPDATE (March 1, 2012): Leroy et al. (2008) added.
UPDATE (June 7, 2011): Kiehl (1983), Charlock (1984), and Slingo & Webb (1997) added.
The Spectral Signature of Recent Climate Change – Brindley & Bantges (2016)
Abstract: “Spectrally resolved measurements of the Earth’s reflected shortwave (RSW) and outgoing longwave radiation (OLR) at the top of the atmosphere intrinsically contain the imprints of a multitude of climate relevant parameters. Here, we review the progress made in directly using such observations to diagnose and attribute change within the Earth system over the past four decades. We show how changes associated with perturbations such as increasing greenhouse gases are expected to be manifested across the spectrum and illustrate the enhanced discriminatory power that spectral resolution provides over broadband radiation measurements. Advances in formal detection and attribution techniques and in the design of climate model evaluation exercises employing spectrally resolved data are highlighted. We illustrate how spectral observations have been used to provide insight into key climate feedback processes and quantify multi-year variability but also indicate potential barriers to further progress. Suggestions for future research priorities in this area are provided.”
Citation: H. E. Brindley, R. J. Bantges (2016), Current Climate Change Reports, DOI: 10.1007/s40641-016-0039-5. [Full text]
Satellite-Based Reconstruction of the Tropical Oceanic Clear-Sky Outgoing Longwave Radiation and Comparison with Climate Models – Gastineau et al. (2014) “The changes of the outgoing longwave radiation (OLR) in clear-sky conditions have been calculated using High Resolution Infrared Radiation Sounder (HIRS) observations from 1979 to 2004. After applying corrections for satellite orbital drift and intercalibration of the HIRS/2 data from the NOAA satellites, the OLR is calculated from a multivariate regression over the tropical ocean region. The clear-sky OLR retrievals compare well with the observed top-of-atmosphere radiation measurements, although the precision and stability uncertainties are larger. While the tropical ocean surface temperature has risen by roughly 0.2 K from 1982 to 2004, the reconstructed OLR remains stable over the ocean. Consequently, there is an increase in the clear-sky greenhouse effect (GHE) of 0.80 W m−2 decade−1. This trend is shown to be larger than the uncertainty in the stability of the HIRS retrievals. The observations are compared with two phase 3 of the Coupled Model Intercomparison Project model ensembles: one ensemble includes both natural and anthropogenic forcings [the twentieth-century (20C) ensemble] and the other ensemble only contains natural climate variability (the control ensemble). The OLR trend in the 20C simulations tends to be more negative than observed, although a majority is found to be within the observational uncertainty. Conversely, the response of the clear-sky OLR to SST is shown to be very similar in observations and models. Therefore, the trend differences between the 20C simulations and observations are likely because of internal climate variability or uncertainties in the external forcings. The observed increase in GHE is shown to be inconsistent with the control ensemble, indicating that anthropogenic forcings are required to reproduce the observed changes in GHE.” Gastineau, Guillaume, Brian J. Soden, Darren L. Jackson, Chris W. O’Dell, 2014: Satellite-Based Reconstruction of the Tropical Oceanic Clear-Sky Outgoing Longwave Radiation and Comparison with Climate Models. J. Climate, 27, 941–957. doi: http://dx.doi.org/10.1175/JCLI-D-13-00047.1. [Full text]
A decade of measured greenhouse forcings from AIRS – Chapman et al. (2013) A conference paper. “Increased greenhouse gasses reduce the transmission of Outgoing Longwave Radiation (OLR) to space along spectral absorption lines eventually causing the Earth’s temperature to rise in order to preserve energy equilibrium. This greenhouse forcing effect can be directly observed in the Outgoing Longwave Spectra (OLS) from space-borne infrared instruments with sufficiently high resolving power 3, 8. In 2001, Harries et. al observed significant increases in greenhouse forcings by direct inter-comparison of the IRIS spectra 1970 and the IMG spectra 19978. We have extended this effort by measuring the annual rate of change of AIRS all-sky Outgoing Longwave Spectra (OLS) with respect to greenhouse forcings. Our calculations make use of a 2°x2° degree monthly gridded Brightness Temperature (BT) product. Decadal trends for AIRS spectra from 2002-2012 indicate continued decrease of -0.06 K/yr in the trend of CO2 BT (700cm-1 and 2250cm-1), a decrease of -0.04 K/yr of O3 BT (1050 cm-1), and a decrease of -0.03 K/yr of the CH4 BT (1300cm-1). Observed decreases in BT trends are expected due to ten years of increased greenhouse gasses even though global surface temperatures have not risen substantially over the last decade.” D. Chapman, P. Nguyen, M. Halem, Proc. SPIE 8743, Algorithms and Technologies for Multispectral, Hyperspectral, and Ultraspectral Imagery XIX, 874313 (May 18, 2013); doi:10.1117/12.2017019.
Spectral signatures of climate change in the Earth’s infrared spectrum between 1970 and 2006 – Chen et al. (2007) Another follow-up paper to Harries et al. (2001), now with fourth spectrum from 2006 in comparison. “Previously published work using satellite observations of the clear sky infrared emitted radiation by the Earth in 1970, 1997 and in 2003 showed the appearance of changes in the outgoing spectrum, which agreed with those expected from known changes in the concentrations of well-mixed greenhouse gases over this period. Thus, the greenhouse forcing of the Earth has been observed to change in response to these concentration changes. In the present work, this analysis is being extended to 2006 using the TES instrument on the AURA spacecraft. Additionally, simulated spectra have been calculated using LBLRTM with inputs from the HadGEM1 coupled model and compared to the observed satellite spectra.” [Full text]
Comparison of Spectrally Resolved Outgoing Longwave Radiation over the Tropical Pacific between 1970 and 2003 Using IRIS, IMG, and AIRS – Griggs & Harries (2007) Based on abstract, this seems to be similar to their 2004 conference paper, so perhaps this is the official publication of that. Abstract: “The observation of changes in the earth’s spectrally resolved outgoing longwave radiation (OLR) provides a direct method of determining changes in the radiative forcing of the climate system. An earlier study showed that satellite-observed changes in the clear-sky outgoing longwave spectrum between 1997 and 1970 from the Infrared Interferometer Spectrometer (IRIS) and Interferometic Monitor of Greenhouse Gases (IMG) instruments could be related to changes in greenhouse gas composition. The authors present a new study that extends this to 2003, through the first use of a new, independent source of global atmospheric infrared spectra, from the Atmospheric Infrared Sounder (AIRS) experiment. AIRS is a dispersion grating spectrometer, while the other two were Fourier transform spectrometers, and this is taken into account in the analysis. The observed difference spectrum between the years 2003 and 1970 generally shows the signatures of greenhouse gas forcing, and also shows the sensitivity of the signatures to interannual variations in temperature. The new 2003 data support the conclusions found in the earlier work, though, interestingly, the methane (CH4) Q branch centered at 1304 cm−1 exhibits more complex behavior, showing a decrease in intensity in the difference spectrum between 1997 and 2003. Sensitivity analysis indicates that this is due to changes in temperature structure, superposed on an underlying increase in CH4. Radiative transfer calculations based on reanalysis data are used to simulate the changes in the OLR spectrum; limitations in such data and possible variations that could account for several observed effects are discussed.” Griggs, J. A., J. E. Harries, 2007: Comparison of Spectrally Resolved Outgoing Longwave Radiation over the Tropical Pacific between 1970 and 2003 Using IRIS, IMG, and AIRS. J. Climate, 20, 3982–4001. doi: http://dx.doi.org/10.1175/JCLI4204.1. [Full text]
Comparison of spectrally resolved outgoing longwave radiation between 1970 and 2003: The ν4 band of methane – Griggs & Harries (2005) “Measurements of spectrally resolved outgoing longwave radiation recorded in 1970, 1997 and 2003 are compared to determine the change in radiative forcing over that period. The changes are shown to be in agreements with that simulated by MODTRAN, a band model, using the known changes in atmospheric temperature and greenhouse gas concentrations when the effects of noise in the observed spectra are considered. The only region where the simulations are unable to reproduce the observations is in the v4 band of methane around 1306cm-1. The methane profiles used to simulate this region of the spectrum are shown to be in good agreement with all available data and the noise levels on the spectra are small. Therefore, it is proposed that the inability to model this region lies in the model formulation. Genln2, a line-by-line model, is shown to give very different results in this particular band to those obtained using MODTRAN. Sensitivity studies show that Genln2 is also not able to fully reproduce the spectrum observed. Errors in the spectroscopic parameters are shown to be smaller than the observed discrepancy and line mixing in methane is suggested as a possible cause of the discrepancy.” Griggs, J & Harries, J 2005, ‘Comparison of spectrally resolved outgoing longwave radiation between 1970 and 2003: The ν4 band of methane’. Proceedings of SPIE, vol 5883. [Full text]
Comparison of spectrally resolved outgoing longwave data between 1970 and present – Griggs & Harries (2004) [Follow-up paper to Harries et al. (2001), now with third spectrum from 2003 in comparison.] “Difference spectra are compared to simulations created using the known changes in greenhouse gases such as CH4, CO2 and O3 over the time period. This provides direct evidence for significant changes in the greenhouse gases over the last 34 years, consistent with concerns over the changes in radiative forcing of the climate.” Jennifer A. Griggs ; John E. Harries, Proc. SPIE 5543, Infrared Spaceborne Remote Sensing XII, 164 (November 4, 2004); doi:10.1117/12.556803 [Full text]
Absolute Spectrally Resolved Radiance: A Benchmark for Climate Monitoring from Space – Anderson et al. (2004) Makes a comparison between two spectra similar to Harries et al. (2001). “We demonstrate how spectra obtained 26 years apart by the IRIS and IMG satellites separate radiative forcing resulting from CO2, CH4, N2O, aerosols etc., from the response of the atmosphere by virtue of the instrument’s spectral resolution.” [Full text]
First global measurement of mid-tropospheric CO2 from NOAA polar satellites: The tropical zone – Chédin et al. (2003) (a conference paper). Measures CO2 concentration but derives the concentration from the outgoing longwave radiation, so practically measures the changes in greenhouse effect of CO2. “Not only the phase of the seasonal variations (location of the peaks) but also their amplitude and their latitudinal evolution match quite well recent in situ observations made by properly equipped commercial airliners measuring in an altitude range similar to the one favoured by the satellite observations. Moreover, the annual trend inferred corresponds to the known increase in the concentration of CO2 as a result of human activities.” [Full text]
Increases in greenhouse forcing inferred from the outgoing longwave radiation spectra of the Earth in 1970 and 1997 – Harries et al. (2001) “The evolution of the Earth’s climate has been extensively studied, and a strong link between increases in surface temperatures and greenhouse gases has been established. But this relationship is complicated by several feedback processes—most importantly the hydrological cycle—that are not well understood. Changes in the Earth’s greenhouse effect can be detected from variations in the spectrum of outgoing longwave radiation, which is a measure of how the Earth cools to space and carries the imprint of the gases that are responsible for the greenhouse effect. Here we analyse the difference between the spectra of the outgoing longwave radiation of the Earth as measured by orbiting spacecraft in 1970 and 1997. We find differences in the spectra that point to long-term changes in atmospheric CH4, CO2 and O3 as well as CFC-11 and CFC-12. Our results provide direct experimental evidence for a significant increase in the Earth’s greenhouse effect that is consistent with concerns over radiative forcing of climate.” John E. Harries, Helen E. Brindley, Pretty J. Sagoo & Richard J. Bantges, Nature 410, 355-357 (15 March 2001) | doi:10.1038/35066553. [Full text, erratum (needs subscription or payment)]
Theories and models
Determining Longwave Forcing and Feedback Using Infrared Spectra and GNSS Radio Occultation – Huang et al. (2010) “The authors investigate whether combining a data type derived from radio occultation (RO) with the infrared spectral data in an optimal detection method improves the quantification of longwave radiative forcing and feedback. Signals derived from a doubled-CO2 experiment in a theoretical study are used. When the uncertainties in both data types are conservatively estimated, jointly detecting the feedbacks of tropospheric temperature and water vapor, stratospheric temperature, and high-level cloud from the two data types should reduce the mean errors by more than 50%. This improvement is achieved because the RO measurement helps disentangle the radiance signals that are ambiguous in the infrared spectrum. The result signifies the complementary information content in infrared spectral and radio occultation data types, which can be effectively combined in optimal detection to accurately quantify the longwave radiative forcing and feedback. The results herein show that the radiative forcing of CO2 and the longwave radiative feedbacks of tropospheric temperature, tropospheric water vapor, and stratospheric temperature can be accurately quantified from the combined data types, with relative errors in their global mean values being less than 4%, 10%, 15%, and 20%, respectively.” Huang, Yi, Stephen S. Leroy, James G. Anderson, 2010: Determining Longwave Forcing and Feedback Using Infrared Spectra and GNSS Radio Occultation. J. Climate, 23, 6027–6035. doi: http://dx.doi.org/10.1175/2010JCLI3588.1. [Full text]
Separation of longwave climate feedbacks from spectral observations – Huang et al. (2010) “We conduct a theoretical investigation into whether changes in the outgoing longwave radiation (OLR) spectrum can be used to constrain longwave greenhouse-gas forcing and climate feedbacks, with a focus on isolating and quantifying their contributions to the total OLR change in all-sky conditions. First, we numerically compute the spectral signals of CO2 forcing and feedbacks of temperature, water vapor, and cloud. Then, we investigate whether we can separate these signals from the total change in the OLR spectrum through an optimal detection method. Uncertainty in optimal detection arises from the uncertainty in the shape of the spectral fingerprints, the natural variability of the OLR spectrum, and a nonlinearity effect due to the cross-correlation of different climate responses. We find that the uncertainties in optimally detected greenhouse-gas forcing, water vapor, and temperature feedbacks are substantially less than their overall magnitudes in a double-CO2 experiment, and thus the detection results are robust. The accuracy in surface temperature and cloud feedbacks, however, is limited by the ambiguity in their fingerprints. Combining ambiguous feedback signals reduces the uncertainty in the combined signal. Auxiliary data are required to fully resolve the difficulty.” Huang, Y., S. Leroy, P. J. Gero, J. Dykema, and J. Anderson (2010), Separation of longwave climate feedbacks from spectral observations, J. Geophys. Res., 115, D07104, doi:10.1029/2009JD012766. [Full text]
Evolution and Trend of the Outgoing Longwave Radiation Spectrum – Huang & Ramaswamy (2009) “The variability and change occurring in the outgoing longwave radiation (OLR) spectrum are investigated by using simulations performed with a Geophysical Fluid Dynamics Laboratory coupled atmosphere–ocean–land general circulation model. First, the variability in unforced climate (natural variability) is simulated. Then, the change of OLR spectrum due to forced changes in climate is analyzed for a continuous 25-yr time series and for the difference between two time periods (1860s and 2000s). Spectrally resolved radiances have more pronounced and complex changes than broadband fluxes. In some spectral regions, the radiance change is dominated by just one controlling factor (e.g., the window region and CO2 band center radiances are controlled by surface and stratospheric temperatures, respectively) and well exceeds the natural variability. In some other spectral bands, the radiance change is influenced by multiple and often competing factors (e.g., the water vapor band radiance is influenced by both water vapor concentration and temperature) and, although still detectable against natural variability at certain frequencies, demands stringent requirements (drift less than 0.1 K decade−1 at spectral resolution no less than 1 cm−1) of observational platforms. The difference between clear-sky and all-sky radiances in the forced climate problem offers a measure of the change in the cloud radiative effect, but with a substantive dependence on the temperature lapse rate change. These results demonstrate that accurate and continuous observations of the OLR spectrum provide an advantageous means for monitoring the changes in the climate system and a stringent means for validating climate models.” Huang, Yi, V. Ramaswamy, 2009: Evolution and Trend of the Outgoing Longwave Radiation Spectrum. J. Climate, 22, 4637–4651. doi: http://dx.doi.org/10.1175/2009JCLI2874.1. [Full text]
Testing Climate Models Using Thermal Infrared Spectra – Leroy et al. (2008) “An approach to test climate models with observations is presented. In this approach, it is possible to directly observe the longwave feedbacks of the climate system in time series of annual average outgoing longwave spectra. Tropospheric temperature, stratospheric temperature, water vapor, and carbon dioxide have clear and distinctive signatures in the infrared spectrum, and it is possible to detect trends of these signals unambiguously from trends in the outgoing longwave spectrum by optimal detection techniques. This approach is applied to clear-sky data in the tropics simulated from the output of an ensemble of climate models. Estimates of the water vapor–longwave feedback by this approach agree to within estimated errors with truth, and it is likely that an uncertainty of 50% can be obtained in 20 yr of a continuous time series. The correlation of tropospheric temperature and water vapor anomalies can provide a constraint on the water vapor–longwave feedback to 5% uncertainty in 20 yr, or 7% in 10 yr. Thus, it should be possible to place a strong constraint on climate models, which currently show a range of 30% in the water vapor–longwave feedback, in just 10 yr. These results may not hold in the presence of clouds, however, and so it may be necessary to supplement time series of outgoing longwave spectra with GPS radio occultation data, which are insensitive to clouds.” Leroy, Stephen, James Anderson, John Dykema, Richard Goody, 2008: Testing Climate Models Using Thermal Infrared Spectra. J. Climate, 21, 1863–1875. doi: http://dx.doi.org/10.1175/2007JCLI2061.1. [Full text]
Simulations of the effects of interannual and decadal variability on the clear-sky outgoing long-wave radiation spectrum – Brindley & Allan (2003) “Using atmospheric profiles derived from the Hadley Centre atmosphere climate model version 3 (HadAM3) as input to a radiative transfer code, the sensitivity of the resolved spectrum of clear-sky outgoing long-wave radiation to both interannual and longer-term atmospheric variability has been analysed. A comparison of the simulated spectra with available observations from two satellite-based instruments indicates a reasonable match, although consistent differences are present. These may be explained by a combination of uncertainties in the atmospheric state, and in the relative calibration of the two instruments. Focusing on the simulations: if HadAM3 is forced by the observed sea surface temperature (SST) record alone, and long-term alterations in the well-mixed greenhouse gases are imposed in the radiance simulations, the changes seen within the major absorption bands are robust. Under a second scenario, where the effects of solar variability, volcanic aerosol, ozone changes and increases in the well-mixed greenhouse gases are also included in the forcing of HadAM3, the long-term profile changes tend to show an enhanced upper-tropospheric warming and low/mid-stratospheric cooling, with increased near-surface humidities compared to the SST-only case. However, the tropospheric response of the system, manifested in the spectral change pattern over the atmospheric window and water vapour bands, falls within the range of year-to-year variability.” Helen E. Brindley, Richard P. Allan, Quarterly Journal of the Royal Meteorological Society, Volume 129, Issue 594, pages 2971–2988, October 2003 Part A. [Full text]
The spectral signature of global warming – Slingo & Webb (1997) “Simulations are presented of the change in the spectrum of the clear-sky outgoing long-wave radiation (OLR) associated with the global warming produced by increases in greenhouse-gas concentrations. the input data for the present day and for the middle of the next century were taken from a recent climate-prediction run of the Hadley Centre Climate Model. the simulations focus on the spectral signature of the warming as opposed to that of the forcing. Stratospheric cooling causes decreases of the OLR in the carbon-dioxide and ozone bands, whilst surface warming increases the OLR in the region of the atmospheric window. the signal in the water-vapour bands is more subtle, due to a near cancellation between the effects of changes in atmospheric temperatures and specific humidities that have little impact on the relative humidity. the residual signal is shown to be related to small changes in upper-tropospheric relative humidity, although at some latitudes this relationship breaks down. It is suggested that satellite observations in the water-vapour bands could be used to provide a quantitative measure of the water-vapour feedback during global warming.” A. Slingo, M. J. Webb, Quarterly Journal of the Royal Meteorological Society, Volume 123, Issue 538, pages 293–307, January 1997 Part B, DOI: 10.1002/qj.49712353803.
Climate variability and trends from operational satellite spectral data – Harries et al. (1995) “‘Fingerprint’ correlation studies of air temperatures have recently suggested the emergence of climate change patterns that are consistent with those simulated by Global Climate Models. Here we investigate the possibility of searching for climate change patterns within directly observed satellite radiance fields in order to utilise the vast amount of data available. As a first example of a technique which could be employed we extend the commonly used pattern matching statistics to develop a ‘spectral‐spatial fingerprint’ method for the detection of climate change. To illustrate the technique, we apply it to two satellite channels: HIRS ch.12, sensitive to upper tropospheric water vapour, and SSU ch.1, sensitive to mid‐stratospheric temperatures centred at 15 hPa.” Harries, J. E., H. E. Brindley, and A. J. Geer (1998), Climate variability and trends from operational satellite spectral data, Geophys. Res. Lett., 25(21), 3975–3978, doi:10.1029/1998GL900056. [Full text]
CO2 induced climatic change and spectral variations in the outgoing terrestrial infrared radiation – Charlock (1984) “The published temperature changes produced in general circulation model simulations of CO2 induced climate modification are used to compute the top of the atmosphere, clear sky outgoing infrared radiance changes expected for doubled CO2. A significant wavenumber shift is produced, with less radiance emerging in the 500–800 cm1 (20.0–12.5 μm) CO2 band and with more emerging in the 800–1200 cm1 (12.5–8.3 μm) window. The effect varies greatly with latitude. The radiance shift in the 2300 cm1 (4.3 μm) region is of the order of 10–30% for doubled CO2. It is suggested that the 2300 cm1 region be carefully monitored as an aid in detecting the climatic effects of increasing CO2. The change in the wavenumber-integrated radiant exitance is at most a few %.” Thomas P. Charlock, Tellus B, Volume 36B, Issue 3, pages 139–148, July 1984, DOI: 10.1111/j.1600-0889.1984.tb00236.x.
Satellite Detection of Effects Due to Increased Atmospheric Carbon Dioxide – Kiehl (1983) “The use of satellites to detect climatic changes due to increased carbon dioxide was investigated. This method has several advantages over ground-based methods of monitoring climatic change. Calculations indicate that, by monitoring the outgoing longwave flux for small intervals in the 15-micrometer spectral region, changes in stratospheric temperatures due to doubled atmospheric carbon dioxide are large enough to be detected above the various sources of noise. This method can be extended to other spectral regions so that causal links between changes in outgoing longwave radiation due to other trace gases and the thermal structure of the atmosphere could be established.” J. T. Kiehl, Science 4 November 1983: Vol. 222 no. 4623 pp. 504-506, DOI: 10.1126/science.222.4623.504.