Much of the debate about the Sun’s role in climate change is centered around reconstructions of solar activity that span the last 400 years, which now include satellite data from the late 1970s to present.
To buttress the claim that solar forcing has effectively played almost no role in surface temperature changessince the mid-20th century, the IPCC has shown a preference for modeled reconstructions of solar activity (i.e., the PMOD) that show a stable or decreasing trend since the 1970s.
Why? Because if the modeled results can depict steady or decreasing solar activity since the last few decades of the 20th century – just as surface temperatures were rising – then attributing the post-1970s warming trend to human activity becomes that much easier.
The trouble is, satellite observations using ACRIM data (which have been affirmed to be accurate by other satellite data sets and are rooted in observation, not modeled expectations) indicate that solar activity did notdecline after the 1970s, but actually rose quite substantially.
It wasn’t until the early 2000s that solar activity began to decline, corresponding with the denouement of the Modern Grand Maximum.
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