Source:
"The dramatic difference between the two estimates of the TSI (Total Solar Irradiance) arises from rival sets of satellite data.
Satellite measurements of TSI began in 1978, the two main sources of data being the Royal Meteorological Institute of Belgium’s so-called ACRIM (Active Cavity Radiometer Irradiance Monitor) composite,
and the World Radiation Center’s PMOD (Physikalisch-Meteorologisches Observatorium Davos) composite.
The ACRIM composite implies that the TSI rose during the 1980s and 1990s but has fallen slightly since then ...
The PMOD composite implies that the TSI has been steadily dropping since the late 1970s ...
The PMOD composite, showing a decline in solar activity during the period after 1975 in which global temperatures went up, therefore downplays the sun’s role in global warming.
On the other hand, the ACRIM composite indicates an increase in solar activity over the same period, so supports the notion that global temperatures are strongly linked to the TSI.
The ACRIM satellite data set and the PMOD data differ in the procedures used to bridge a two-year gap in ACRIM data around 1990.
The gap in data gathering occurred after the launch of a new ACRIM satellite was delayed by the Challenger disaster.
It’s these disparate gap-bridging procedures that result in the ACRIM and PMOD composite data showing such different behavior of the TSI during solar cycles 21 to 23.
The authors of the recent paper also discuss other TSI reconstructions, some of which support the ACRIM data and some of which back the rival PMOD data.
Rather than passing judgment on which dataset is the better representation of reality, the authors urge the climate science community to consider all relevant estimates of the TSI and not just the one illustrated in the first figure above.
But they conclude that, contrary to the current narrative, the question of how much the sun has influenced recent global temperatures
– at least in the Northern Hemisphere –
has not yet been answered satisfactorily.
The researchers go on to comment:
“The PMOD dataset is more politically advantageous to justify the ongoing considerable political and social efforts to reduce greenhouse gas emissions
under the assumption that the observed global warming since the late 19th century is mostly due to greenhouse gases.”
They add that political considerations have been acknowledged as one of the motivations for the development of the PMOD composite as a rival dataset to the ACRIM measurements."
The PMOD composite implies that the TSI has been steadily dropping since the late 1970s ...
The PMOD composite, showing a decline in solar activity during the period after 1975 in which global temperatures went up, therefore downplays the sun’s role in global warming.
On the other hand, the ACRIM composite indicates an increase in solar activity over the same period, so supports the notion that global temperatures are strongly linked to the TSI.
The ACRIM satellite data set and the PMOD data differ in the procedures used to bridge a two-year gap in ACRIM data around 1990.
The gap in data gathering occurred after the launch of a new ACRIM satellite was delayed by the Challenger disaster.
It’s these disparate gap-bridging procedures that result in the ACRIM and PMOD composite data showing such different behavior of the TSI during solar cycles 21 to 23.
The authors of the recent paper also discuss other TSI reconstructions, some of which support the ACRIM data and some of which back the rival PMOD data.
Rather than passing judgment on which dataset is the better representation of reality, the authors urge the climate science community to consider all relevant estimates of the TSI and not just the one illustrated in the first figure above.
But they conclude that, contrary to the current narrative, the question of how much the sun has influenced recent global temperatures
– at least in the Northern Hemisphere –
has not yet been answered satisfactorily.
The researchers go on to comment:
“The PMOD dataset is more politically advantageous to justify the ongoing considerable political and social efforts to reduce greenhouse gas emissions
under the assumption that the observed global warming since the late 19th century is mostly due to greenhouse gases.”
They add that political considerations have been acknowledged as one of the motivations for the development of the PMOD composite as a rival dataset to the ACRIM measurements."