New paper finds large surface solar radiation increase of 4% per decade & UV increase 7% per decade

A paper published today in Atmospheric Chemistry and Physics finds global solar radiation at the surface in Belgium has significantly and substantially increased by 4% per decade from 1991-2013, and solar UV radiation at the surface has increased even more by 7% per decade. 

According to the authors, the findings corroborate others for Europe as well as the well-known global brightening phenomenon, which followed the global dimming period from ~1970-1985 that was responsible for the ice age scare of the 1970's.  

The authors find a (statistically insignificant) decrease of aerosol optical depth of -8%/decade from 1991-2013, which could be due to a decrease of cloud cover and/or other aerosols. As noted by Dr. Roy Spencer, a mere 1-2% change in cloud cover can alone account for global warming or cooling. 

The authors also find total column ozone, which is primarily generated by solar UV and can act as a solar amplification mechanism, has increased by 3%/decade. 

The effects of solar dimming and brightening on climate are far greater than attributed to greenhouse gases, but which have not been simulated by climate models. These observed trends of solar surface radiation dimming and brightening correspond well to the observed global temperature changes over the past 50 years, and to a far greater extent than do CO2 levels.  

Findings from the paper:

erythemal ultraviolet (UV) dose (Sery):   +7%/decade

global solar radiation (Sg):                 +4%/decade

total ozone column:                                +3%/decade

aerosol optical depth:                            -8%/decade (insignificant)

Excerpt:

Global solar radiation

Concerning the global solar radiation, many publications

agree on the existence of a solar dimming period between

1970 and 1985 and a subsequent solar brightening

period (Norris and Wild, 2007; Solomon et al.,

2007; Makowski et al., 2009; Stjern et al., 2009; Wild

et al., 2009; Sanchez-Lorenzo and Wild, 2012). Different

studies have calculated the trend in Sg after 1985.

The trend in Sg [global solar radiation] from GEBA (Global 

Energy Balance Archive; between 1987 and 2002 is

equal to +1.4 ( 3.4)Wm-2 per decade according to Norris

and Wild (2007). Stjern et al. (2009) found a total change

in the mean surface solar radiation trend over 11 stations

in northern Europe of +4.4% between 1983 and 2003. In

the Fourth Assessment Report of the IPCC (Solomon et al.,

2007), 421 sites were analyzed; between 1992 and 2002,

the change of all-sky surface solar radiation was equal to

0.66Wm-2 per year. Wild et al. (2009) investigated the

global solar radiation from 133 stations from GEBA/World

Radiation Data Centre belonging to different regions in Europe.

All series showed an increase over the entire period,

with a pronounced upward tendency since 2000. For

the Benelux region, the linear change between 1985 and

2005 is equal to +0.42Wm-2 per year, compared to the

pan-European average trend of +0.33Wm-2 per year (or

+0.24Wm-2 if the anomaly of the 2003 heat wave is excluded)

(Wild et al. 2009). Our trend at Uccle of +0.5

( 0.2)Wm-2 per year (or +4% per decade) agrees within

the error bars with the results from Wild et al. (2009).

Relations between erythemal UV dose, global solar radiation, total ozone column and aerosol optical depth at Uccle, Belgium

Atmospheric Chemistry and Physics, 14, 12251-12270, 2014

Author(s): V. De Bock, H. De Backer, R. Van Malderen, A. Mangold, and A. Delcloo

At Uccle, Belgium, a long time series (1991–2013) of simultaneous measurements of erythemal ultraviolet (UV) dose (Sery), global solar radiation (Sg), total ozone column (Q_{O3}$) and aerosol optical depth (τaer) (at 320.1 nm) is available, which allows for an extensive study of the changes in the variables over time. Linear trends were determined for the different monthly anomalies time series. Sery, Sg and QO3 all increase by respectively 7, 4 and 3% per decade. τaer shows an insignificant negative trend of −8% per decade. These trends agree with results found in the literature for sites with comparable latitudes. A change-point analysis, which determines whether there is a significant change in the mean of the time series, is applied to the monthly anomalies time series of the variables. Only for Sery and QO3, was a significant change point present in the time series around February 1998 and March 1998, respectively. The change point in QO3corresponds with results found in the literature, where the change in ozone levels around 1997 is attributed to the recovery of ozone. A multiple linear regression (MLR) analysis is applied to the data in order to study the influence of Sg, QO3 and τaer on Sery. Together these parameters are able to explain 94% of the variation in Sery. Most of the variation (56%) in Sery is explained by Sg. The regression model performs well, with a slight tendency to underestimate the measured Sery values and with a mean absolute bias error (MABE) of 18%. However, in winter, negative Sery are modeled. Applying the MLR to the individual seasons solves this issue. The seasonal models have an adjusted R2 value higher than 0.8 and the correlation between modeled and measured Sery values is higher than 0.9 for each season. The summer model gives the best performance, with an absolute mean error of only 6%. However, the seasonal regression models do not always represent reality, where an increase in Sery is accompanied with an increase in QO3 and a decrease in τaer. In all seasonal models, Sg is the factor that contributes the most to the variation in Sery, so there is no doubt about the necessity to include this factor in the regression models. The individual contribution of τaer to Sery is very low, and for this reason it seems unnecessary to include τaer in the MLR analysis. Including QO3, however, is justified to increase the adjusted R2 and to decrease the MABE of the model.