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Saturday, April 18, 2015

Volcanic contribution to decadal changes in tropospheric temperature




Despite continued growth in atmospheric levels of greenhouse gases, global mean surface and tropospheric temperatures have shown slower warming since 1998 than previously12345. Possible explanations for the slow-down include internal climate variability3467, external cooling influences124891011 and observational errors1213. Several recent modelling studies have examined the contribution of early twenty-first-century volcanic eruptions1248 to the muted surface warming. Here we present a detailed analysis of the impact of recent volcanic forcing on tropospheric temperature, based on observations as well as climate model simulations. We identify statistically significant correlations between observations of stratospheric aerosol optical depth and satellite-based estimates of both tropospheric temperature and short-wave fluxes at the top of the atmosphere. We show that climate model simulations without the effects of early twenty-first-century volcanic eruptions overestimate the tropospheric warming observed since 1998. In two simulations with more realistic volcanic influences following the 1991 Pinatubo eruption, differences between simulated and observed tropospheric temperature trends over the period 1998 to 2012 are up to 15% smaller, with large uncertainties in the magnitude of the effect. To reduce these uncertainties, better observations of eruption-specific properties of volcanic aerosols are needed, as well as improved representation of these eruption-specific properties in climate model simulations.

At a glance

Figures

left
  1. Modelled and observed near-global (82.5[deg] N-70[deg] S) monthly mean TLT anomalies before and after statistical removal of ENSO and volcano signals.
    Figure 1
  2. Effect of recent volcanic eruptions on atmospheric temperature.
    Figure 2
  3. Statistical significance of observed tropical (20[deg] N-20[deg] S) climate signals after late twentieth- and early twenty-first-century volcanic eruptions.
    Figure 3
  4. Behaviour of overlapping 10-year trends in the /`ENSO removed/' near-global (82.5[deg] N-70[deg] S) TLT data.
    Figure 4
right
  1. Solomon, S. et alThe persistently variable ‘background’ stratospheric aerosol layer and global climate changeScience 333866870 (2011).
  2. Fyfe, J. C.von Salzen, K.Cole, J. N. S.Gillett, N. P. & Vernier, J-P. Surface response to stratospheric aerosol changes in a coupled atmosphere–ocean modelGeophys. Res. Lett.40584588 (2013).
  3. Santer, B. D. et alSeparating signal and noise in atmospheric temperature changes: The importance of timescaleJ. Geophys. Res. 116D22105 (2011).
  4. Fyfe, J. C.Gillett, N. P. & Zwiers, F. W. Overestimated global warming over the past 20 yearsNature Clim. Change 3767769 (2013).
  5. Santer, B. D. et alIdentifying human influences on atmospheric temperatureProc. Natl. Acad. Sci. USA 1102633 (2013).
  6. Meehl, G. A.Arblaster, J. M.Fasullo, J. T.Hu, A. & Trenberth, K. E. Model-based evidence of deep-ocean heat uptake during surface-temperature hiatus periodsNature Clim. Change1360364 (2011).
  7. Kosaka, K. & Xie, S-P. Recent global-warming hiatus tied to equatorial Pacific surface cooling.Nature 501403407 (2013).
  8. Haywood, J. M.Jones, A. & Jones, G. S. The impact of volcanic eruptions in the period 2000-2013 on global mean temperature trends evaluated in the HadGEM2-ES climate model.Atmos. Sci. Lett. (2013)doi:10.1002/asl2.471
  9. Kopp, G. & Lean, J. L. A new, lower value of total solar irradiance: Evidence and climate significanceGeophys. Res. Lett. 38L01706 (2011).
  10. Solomon, S. et alContributions of stratospheric water vapour to decadal changes in the rate of global warmingScience 32712191223 (2010).
  11. Shindell, D. T. et alRadiative forcing in the ACCMIP historical and future climate simulations.Atmos. Chem. Phys. 1329392974 (2013).
  12. Morice, C. P.Kennedy, J. J.Rayner, N. A. & Jones, P. D. Quantifying uncertainties in global and regional temperature change using an ensemble of observational estimates: The HadCRUT4 data setJ. Geophys. Res. 117D08101 (2012).
  13. Mears, C.Wentz, F. J.Thorne, P. & Bernie, D. Assessing uncertainty in estimates of atmospheric temperature changes from MSU and AMSU using a Monte-Carlo techniqueJ. Geophys. Res. 116D08112 (2011).
  14. Christy, J. R.Norris, W. B.Spencer, R. W. & Hnilo, J. J. Tropospheric temperature change since 1979 from tropical radiosonde and satellite measurementsJ. Geophys. Res. 112,D06102 (2007).
  15. Cowtan, K. & Way, R. G. Coverage bias in the HadCRUT4 temperature series and its impact on recent temperature trends, Quart. J. Roy. Met. Soc.http://dx.doi.org/10.1002/qj.2297 (in the press)
  16. Taylor, K. E.Stouffer, R. J. & Meehl, G. A. An overview of CMIP5 and the experiment design.Bull. Amer. Meteor. Soc. (2012)doi:10.1175/BAMS-D-11-00094.1
  17. Robock, A. Volcanic eruptions and climateRev. Geophys. 38191219 (2000).
  18. Sato, M.Hansen, J. E.McCormick, M. P. & Pollack, J. B. Stratospheric aerosol optical depth, 1850–1990J. Geophys. Res. 982298722994 (1993).
  19. Ramaswamy, V. et alAnthropogenic and natural influences in the evolution of lower stratospheric coolingScience 31111381141 (2006).
  20. Wigley, T M L.Ammann, C. M.Santer, B. D. & Raper, S C B. The effect of climate sensitivity on the response to volcanic forcingJ. Geophys. Res. 110D09107 (2005).
  21. Santer, B. D. et alAccounting for the effects of volcanoes and ENSO in comparisons of modeled and observed temperature trendsJ. Geophys. Res. 1062803328059 (2001).
  22. Thompson, D W J.Wallace, J. M.Jones, P. D. & Kennedy, J. J. Identifying signatures of natural climate variability in time series of global-mean surface temperature: Methodology and insightsJ. Clim. 2261206141 (2009).
  23. Smith, T. M.Reynolds, R. W.Peterson, T. C. & Lawrimore, J. Improvements to NOAA’s historical merged land-ocean surface temperature analysis (1880–2006)J. Clim. 21,22832296 (2008).
  24. Vernier, J.-P. et alMajor influence of tropical volcanic eruptions on the stratospheric aerosol layer during the last decadeGeophys. Res. Lett. 38L12807 (2011).
  25. Neely III, R. R. et alRecent anthropogenic increases in SO2 from Asia have minimal impact on stratospheric aerosolGeophys. Res. Lett. 40 (2013)doi:10.1002grl.50263
  26. Loeb, N. G. et alTowards optimal closure of the earth’s top-of-atmosphere radiation budget.J. Climate 22748766 (2009).
  27. Muller, R.http://www.nytimes.com/2013/09/26/opinion/a-pause-not-an-end-to-warming.html?_r=0
  28. Christy, J. R. Testimony in Hearing before the Subcommittee on Energy and Power, Committee on Energy and Commerce, House of Representatives, March 8, 2011.http://republicans.energycommerce.house.gov/Media/file/Hearings/Energy/030811/Christy.pdf
  29. Hassler, B. et alComparison of three vertically resolved ozone data sets: Climatology, trends and radiative forcingsAtmos. Chem. Phys. 1355335550 (2013).
  30. Eyring, V. et alLong-term ozone changes and associated climate impacts in CMIP5 simulationsJ. Geophys. Res. 11850295060 (2013).
  31. http://www.nature.com/ngeo/journal/v7/n3/full/ngeo2098.html

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