Total solar irradiance, also called “TSI”, is the total amount of energy coming from the sun at all frequencies. It is measured in watts per square metre (W/m2). Lots of folks claim that the small ~ 11-year variations in TSI are amplified by some unspecified mechanism, and thus these small changes in TSI make an observable difference in some aspect of the temperature.
In that regard, here are the monthly variations in TSI (as a global 24/7 average) as shown by the CERES data:
Figure 1. Variations in TSI. The upper panel (red) shows the actual measured TSI. The middle panel shows the seasonal component of that variation. The bottom panel shows the ~ eleven-year variation in TSI once the seasonal data has been removed.
There are oddities in this record. Overall, the ~ eleven-year variation is a bit more than a quarter of a W/m2. However, from late 2000 to early 2001, the TSI dropped a bit more than a quarter of a W/m2. However, I digress …
My question is, if the tiny eleven-year changes in TSI of a quarter of a W/m2 cause an observable change in the temperature, then where is the effect of the ~ 22 W/m2 annual variation in the amount of sun hitting the earth? That annual change is a hundred times the size of the eleven-year TSI change. Where is the effect of that 22 W/m2 change?
To get an idea of the predicted effect of this variation in TSI, using IPCC figures this TSI change of 22 W/m2 is about the same change in forcing that we would get from six doublings of CO2 … that is to say, CO2 going from the current level (400 ppmv) to the extraordinary level of 25,600 ppmv.
In addition, again according to the IPCC, using their central value of 3°C warming per doubling of CO2 (3.7 W/m2 additional forcing), this change in forcing should be accompanied by a change in temperature of no less than 18°C (32°F).
Now, I can accept that this would be somewhat reduced because of the thermal lag of the climate system. But the transient (immediate) climate response to increased forcing is said to be on the order of 2°C per doubling of CO2. So this still should result in a warming of 12°C (22°F) … and we see nothing of the sort.
I say this lack of an effect of the TSI changes is because the climate system responds to the current conditions. The climate system is not some inanimate object that is simply pushed around by external forcings. Instead, it reacts, it responds, it evolves and varies based on the instantaneous local situations everywhere. In particular, when it is cold we get less tropical clouds, and that increases the energy entering the system. And similarly, when it is warm we get more tropical clouds, cutting out huge amounts of incoming energy by reflecting it back to space. In this way, the system reacts to maintain the same temperature despite the changes in forcing.
However, I’m happy to listen to alternate explanations and to consider opposing evidence … so if you think that the IPCC is right when it says that changes in temperature are driven by the changes in forcing, I ask you why the annual forcing change of 22 W/m2 doesn’t seem to show a corresponding 12°C change in global temperature.
Best to everyone,
My Request—if you disagree with someone, please quote the exact words you disagree with. This allows us all to understand just what you think is incorrect.