According to its own statutes, the IPCC is mainly responsible for anthropogenic climate change - and much less so for natural climate change, which has been around since the Earth first appeared. That could very well be the reason why the sun gets mentioned only with respect to its solar irradiance intensity at the edge of the atmosphere. There the irradiance is 1361 W/sqm and is relatively constant, and so the role of the sun on mid-term climate change is not taken into account.

However, for the first time in the history of the IPCC reports, the 2013 AR5 report discusses the Surface Solar Radiation (SSR) as a decisively important factor (chapter 2.3.3.). Decisive for the climate and temperature changes is not the solar irradiance at the edge of the atmosphere, rather it is the amount of solar energy that makes it to the Earth's surface.

Between the Earth's surface and the outer edge of the atmosphere we have the atmosphere with its clouds and aerosols, which determine how much solar radiation eventually reaches the surface of the Earth. Since 1983 the International Satellite Cloud Climatology Program (ISCCP) has been measuring global cloud coverage. One spectacular result was the decrease in global cloud cover between 1987 - 2000, from 69% to 64%, i.e. precisely during the period of warming that triggered the CO2 hypothesis.

global cloud coverage
© ISCCP
Figure 1: Mid-term variation of mean global cloud coverage according to data from the ISCCP for the period 1983 to 2010.

Of course this finding did not fit well with the current popular narrative and was immediately criticized and doubted. This prevented it being adopted by the IPCC report of 2007. Indeed cloud observation and the evaluation of the data from satellites are difficult and the results are subject to interpretation. But in the meantime we have recognized that there is an objective method of determining the effects of clouds and the impact of solar dimming: by measuring the effective solar radiation at the surface of the Earth. For the first time this is discussed in the new IPCC report in Chapter 2.3.3 and is confirmed by the longest existing dataset from Stockholm. It shows a clear fluctuation of solar energy between 90 and 135 W/sqm. And the range is considerably greater at lower latitudes.

solar insolation Stockholm
© Unknown
Figure 2: Effective solar insolation at the Earth’s surface for Stockholm 1922-2010 (59° north latitude).
The data from Stockholm not only correspond to the ISCCP-results, but also to the global temperature trends. Not only do the rise of global temperature and SSR correspond between 1910 and 1940, but also for the temperature drop between 1944 and 1980, and the rise until 2000. Figure 3 shows a comparison of 10 temperature curves from 10 global weather stations, without the statistical manipulations of a so-called "global mean temperature".

Real global temperature
© Unknown
Figure 3: Real temperature measurement values from cities on the globe.
The SSR curve correlates excellently with the original GISS dataset for the US temperature history in 1999, before it was tampered with.

USA GISS temperature history
© GISS
Figure 4: The original GISS temperature history for the USA as it looked in 1999. It was then replaced by a new curve which moved the maximum value to the year 1998.
Even if the important SSR factor gets mentioned for the first time in an IPCC report, this does not mean it was taken into account in other chapters of the report, and especially for the temperature development - to the contrary - it was ignored. Only the CO2 hypothesis is valid. Here the entire 0.8°C temperature rise of the last 100 years, for which part or all of it gets attributed to CO2, can be explained by the impacts of the effective solar radiation at the Earth's surface without any CO2 effects.

Already the temperature rise of 0.6°C between 1910 and 1940 cannot be explained by the CO2 effect because the CO2 concentration increased by less than 10 ppm during the period (from 298 to 307 ppm). Then from 1940 to 1975 the temperature fell 0.2°C - and certainly not because of a CO2 drop. The renewed temperature increase of 0.6°C from 1980 to 1998 was the initiator of the CO2 hypothesis. However, the temperature increase can be better explained by the increase in SSR intensity. The fact that the predicted continued temperature increase never materialized, and that there's been a slight drop since 2000, completely contradicts the CO2 hypothesis.