Probably not. But the measurements are not accurate enough to be sure. Only satellite observations really count. Changes in levels of air pollution over the past 30 years throw ground based measurements off. As might be expected, the measurements from different satellites are different by a small mount. For instance Nimbus 7 , launched in 1978 and out of service by 1993, gives Total Solar Irradiation as 1373 watts per square meter. The ACRIM 1 satellite, active from 1980 to 1990, gives a lower number of 1368 watts per square meter. Other satellites give other numbers. The spread from high to low from 1978 to today is about 0.6 percent.
The raw data suggests that the sun has cooled off by 0.6% since 1978. But it's more convincing to say that modern satellites read just a little bit lower than the first satellite launched 30 years ago. It is possible to correct the satellite data to make them read the same. If this is done, some conclude that the Sun has cooled by 0.047% but others say the corrections should be done differently.
All of the satellites are/were sensitive enough to see the 11 year sunspot cycle. From sunspot max to sunspot min is about 0.1%. Personally I think the change in solar output over the sunspot cycle is too small to effect weather or climate. No one has shown an 11 year cycle in any sort of earth weather data. The long term change in solar output, after corrections, is smaller than the sunspot variation.
Bottom line, the long term change in solar output is too small to see reliably with current satellites, the change (if any) is too small to detect.
This data makes it hard for me to believe that solar variation has anything to do with global warming since 1978.
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