IAU misreports climate change/sunspot link

Giant sunspot group AR1944 seen in January of 2014. Credit: NASA/SDO

IAU press release emphasizes no global warming sunspot link, but fails to report sunspot related global cooling

PHOENIX, Aug 20, 2015 – On August 7th a press release on sunspot activity provided during the annual meeting of the International Astronomical Union (IAU) received coverage in dozens of newspapers and popular science journals all over the world.

An important finding presented at the meeting and included in the press release correctly emphasized that the newly recalibrated solar sunspot record shows that solar activity in the last 300 years is not responsible for observed global warming in the last century. Skeptics have long alleged that it did.

An equally important, but largely ignored, sentence in the press release says:
The Maunder Minimum, between 1645 and 1715, when sunspots were scarce and the winters harsh, strongly suggests a link between solar activity and climate change.

In 1976 astronomer John Eddy published a landmark paper in Science titled “The Maunder Minimum” where he first established the link between low sunspot activity and cooler earth temperatures. The Maunder Minimum was over 300 years ago.

Group sunspot tallies going back to 1610 show three solar induced cooling periods. Credit: Steve Davidson/SILSO data

Group sunspot tallies going back to 1610 show three solar induced cooling periods. Credit: Steve Davidson/SILSO data

Unmentioned in the press release is that solar activity has altered climate three times in the last 400 years. Each time resulted in global cooling and it’s about to happen again. The three cooler times are the Maunder, Dalton and a weak unnamed minimum between 1880 and 1915.

The weakest of the three solar-induced cooling trends occurred during the unnamed minimum. It’s the only one documented in the IPCC’s HadCRUT4 global land-sea temperature database, which only goes back to 1850. The first two, the Maunder and Dalton, were before 1850.

It’s evidence-based speculation at this time, but the current trend in solar activity shown above indicates another minimum of solar activity, tentatively name the “Eddy Minimum”, is on its way. The IPCC has already said that lower sunspot activity will slow global warming over the next few decades, but not reverse it.

Sunspot activity compared to global land-sea temperatures since 1850. Credit Steve Davidson//Wood for Trees data

Sunspot activity compared to global land-sea temperatures since 1850. Credit: Steve Davidson/Wood for Trees data

The above graph shows the newly revised monthly sunspot counts (in red) compared with the IPCC’s HadCRUT4 global land-sea database (in green). Note the trend lines shown between 1880 and 1948.

The graph shows three important things:

  1. No sunspot/temperature link after 1978
  2. A weak cooling trend and sunspot link from 1880-1915
  3. A weak warming trend and sunspot link from 1915-1948

Item one disproves that current global warming since 1950 is caused by solar activity, as wrongly postulated by some skeptics. It supports human-caused global warming theory in that dramatic warming since 1978 can’t be attributed to solar activity alone.

Items 2 and 3, the weak solar-linked cooling and warming trends between 1880 and 1948 shows the last and weakest of the three solar-related cooling periods documented in the revised 400-year sunspot record.

Also unmentioned in the IAU press release is there is strong evidence that right now we are heading into another dip in solar activity, the “Eddy Minimum”, over the next decades that will have a cooling effect that the IPCC has already acknowledged.

Even though the newly revised sunspot record shows that current global warming is not caused by solar activity over the last 300 years, it just as clearly shows that variations in solar activity is related to climate cooling periods that last for decades.

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