Those figures look to be based on a 4 kw system and the gross kwh are not based on degradation rate of 0.4%.
Anyway you are looking at the overall CO2 which you can only assume every solar system is perfect and going to last 20 years, which in reality I would doubt that.
The figures quoted are for CO2 produced already so as the cycle grows every day you never cut that CO2 production off or offset it to what some think.
It is a dog eat dog situation, there are no real winners.
