Solar Activity Drives Climate Change
Has solar activity influenced Earth climate over geologic time? If so, how does it change climate? How will ongoing solar activity alter climate in our immediate future?
It seems a silly notion to ignore the primary source of heat and light on Earth when talking about climate change.
Yet, that is exactly what the IPCC has done in every climate assessment report, including AR5 just released.
The IPCC ignores the sun! It’s justification is total solar irradiance (TSI) varies by only ±0.5 W/m2 measured over the last 3 solar cycles.
According to the IPCC, greenhouse gases have trapped 1.7 W/m2 of heating. That is more than 3 times greater cumulative influence than solar variability. The IPCC also estimates the average drop in TSI during the Maunder Minimun cold period of the 1600s was -0.16 W/m2. Greenhouse gases have had 10 time more influence than that.
TSI, the total energy from the sun, links directly to the 11-year sunspot cycle. High sunspots raises TSI and warms the Earth. Low sunspots lower it and cools the Earth.
Geologically speaking, 33 years of measured TSI is the blink of an eye. How has TSI varied over the long term?
A 2008 study called “Grand Minima and maxima of solar activity: New observational constraints (.pdf)” published in Astronomy and Astrophysics provides some answers.
Solar Activity During the Holocene
In geologic time, we are living in the Holocene Epoch. Paleoclimatologists call this epoch an “interglacial warm period”. It began 11,500 years at the end of the last great ice age expansion.
Direct TSI measurements go back only 30 years. For longer periods scientist depend on solar activity reconstructions that imply larger TSI variability.
The above graph is a solar sunspot activity reconstruction smoothed for the entire Holocene. It’s from the 2008 study. What does it tell us?
- At present the sun is at its most active in 10,000 years
- In the mid-1600s during the “little ice age” solar activity was nil
- The sun was most active 11,000 years ago when the great ice sheets melted
The sun was very active in the last century and the Earth got hotter.
Solar activity was nil during the “little ice age” and the Earth was colder.
11,000 years ago, at the beginning of the Holocene, the sun was at its most active when the vast ice sheets covering Europe and North America all melted away.
Coincidence?… perhaps NOT!
The warmest earth climate corresponds with the highest amounts of smoothed sunspot activity during periods named Grand Maxima. The coldest periods, like the “little ice age” correspond to times of low solar activity during so-called Grand Minima.
The IPCC argues that the sun hasn’t had much impact because of a mere 30-year period of measured TSI variability. The long-term reconstruction from the 2008 study argues otherwise. Both hot and cold periods on Earth throughout the Holocene provides strong evidence that solar variability plays a major role in Earth’s climate.
That should surprise no one except for… wellll… the IPCC!!
A lot has happened since 2008. Earth’s sun is undergoing its most rapid change since the Maunder Minimum 400 years ago!
As shown in the graph above, less than a century ago the sun was at a peak of solar sunspot activity. Cycle 19 was up around 200. But in the last two cycles solar activity has plummeted to only 67 this cycle. Next cycle is forecast to only be a stunning 7 spot average! Solar activity is dying. That is HUGE news.
If that comes to pass, and all indicators suggest it will, then we are headed for another phase matching the Maunder Minimum of the little ice age.
Those of you concerned about global warming take heed. Don’t throw away your fur-lined winter overcoat just yet. You might need it.