Global Dimming and Brightening

A fundamental determinant of climate and life on our planet is the solar radiation (sunlight) incident at the Earth’s surface. Any change in this precious energy source affects our habitats profoundly. Until recently, for simplicity and lack of better knowledge, the amount of solar radiation received at the Earth surface was assumed to be stable over the years. However, there is increasing observational evidence that this quantity undergoes significant multi-decadal variations, which need to be accounted for in discussions of climate change and mitigation strategies. Specifically, we noted a decrease of surface solar radiation from the 1950s to the 1980s in the worldwide observational networks ("global dimming") and a more recent recovery ("brightening"), (Wild et al. 2005, Wild 2009, 2012, 2016). These variations are often in accord with anthropogenic air pollution patterns. We investigate the main characteristics of this phenomenon, its underlying causes, and potential environmental implications. In order to reproduce these trends in climate models and estimate their impacts on other components of the climate system, the inclusion of sophisticated schemes of aerosol and cloud microphysics are essential. Such schemes are implemented in the latest versions of the ECHAM-HAM and CLM model series available at ETH. Extended transient experiments are carried out with these comprehensive modeling systems to investigate the origins, magnitude and impacts of global dimming and brightening both over land and ocean surfaces. These modeling studies are accompanied by diagnostic studies based on observational records from the Global Energy Balance Archive maintained in this group.

Enlarged view: SSR time series Potsdam
Annual mean surface solar radiation (in Wm-2) as observed at Potsdam, Germany, from 1937 to 2014. Five year moving average in blue. Distinct phases of inclines (1930s–1940s, ‘early brightening’), declines (1950s–1980s, ‘dimming’), and renewed inclines (since 1980s, ‘brightening’) can be seen. Units Wm-2. In addition, a stabilization since around 2010 can be noted (from Wild 2015, WIRES Clim Change)

Wild, M., Gilgen, H., Roesch, A., Ohmura, A., Long, C., Dutton, E., Forgan, B., Kallis, A., Russak, V., and Tsvetkov, A., 2005: From dimming to brightening: Decadal changes in solar radiation at the Earth’s surface. Science, 308, 847-850.

Norris, J.R., and Wild, M., 2007: Trends in direct and indirect aerosol radiative effects over Europe inferred from observed solar “dimming” and “brightening”, J. Geophys. Res. 112, D08214, doi:10.1029/2006JD007794.

Wild, M., Ohmura, A., Makowski, K., 2007: Impact of global dimming and brightening on global warming. Geophys. Res. Lett., 34, L04702, doi:10.1029/2006GL028031.

Wild, M., 2009: How well do the IPCC AR4/CMIP3 models simulate global dimming and brightening and related effects on 20th century day- and nighttime warming? J. Geophys. Res., 114, D00D11, doi:10.1029/2008JD011372.

Wild, M., Trüssel, B., Ohmura, A., Long, C.N. König-Langlo G., Dutton, E.G., and Tsvetkov, A., 2009: Global Dimming and Brightening: an update beyond 2000. J. Geophys. Res., 114, D00D13, doi:10.1029/2008JD011382.

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, 1014-1018.

Wild, M., 2009: Global dimming and brightening: A review. J. Geophys. Res. 114, D00D16, doi:10.1029/2008JD011470.

Folini, D., and Wild, M., 2011: Aerosol Emissions and Dimming / Brightening in Europe: sensitivity studies with ECHAM5-HAM, J. Geophys. Res., 116, D21104, doi:10.1029/2011JD016227.

Wild, M. 2012: Enlightening Global Dimming and Brightening. Bull. Amer. Meteor. Soc., 93, 27–37, doi:10.1175/BAMS-D-11-00074.1

Folini, D., and Wild, M., 2015: The effect of aerosols and sea surface temperature on China's climate in the late twentieth century from ensembles of global climate simulations, J. Geophys. Res. Atmos., 120, 2261-2279, DOI: 10.1002/2014JD022851.

Dallafior, T. N., Folini, D., Knutti, R., and Wild, M., 2015: Dimming over the oceans: Transient anthropogenic aerosol plumes in the twentieth century, J. Geophys. Res. Atmos., 120, 3465–3484, doi:10.1002/2014JD022658.

Sanchez-Lorenzo, A., Wild, M., Brunetti, M., Guijarro, J. A., Hakuba, M. Z., Calbó, J., Mystakidis, S., and Bartok, B. 2015: Reassessment and update of long-term trends in downward surface shortwave radiation over Europe (1939–2012), J. Geophys. Res. Atmos., 120, 9555-9569, doi:10.1002/2015JD023321.

Manara, V., Brunetti, M., Celozzi, A., Maugeri, M., Sanchez-Lorenzo, A., and Wild, M., 2016: Detection of dimming/brightening in Italy from homogenized all-sky and clear-sky surface solar radiation records and underlying causes (1959–2013), Atmos. Chem. Phys.,16, 11145-11161, doi:10.5194/acp-16-11145-2016.

Wild, M., 2016 Decadal changes in radiative fluxes at land and ocean surfaces and their relevance for global warming, WIRES Clim Change, doi: 10.1002/wcc.372

Folini, D., Dallafior, T. N., Hakuba, M. Z., and Wild, M., 2017: Trends of surface solar radiation in unforced CMIP5 simulations. J. Geophys. Res., 122, 469–484, doi:10.1002/2016JD025869.

Yang, S., Wang, X.L., and Wild, M., 2018: Homogenization and trend analysis of the 1958-2016 in-situ surface solar radiation records in China, J. Climate, 31, 4529-4541, doi: 10.1175/JCLI-D-17-0891.

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