No Climate Emergency? No, Most Climate Change Appears to Be Solar Related!

The great Judith Curry has published an excellent and extremely well written post by Javier Vinós on her site. It’s titled “How We Know That the Sun Changes the Climate.” Only “Part I: The Past” is up right now but it’s full of great stuff and I look foward to Parts II and III, as I’m sure readers will as well. Here is condensed version of the current post:

There are many natural causes that change the climate, and what we need to know is whether the Sun is one of the main ones.

To find out, we don’t need to care what the IPCC and NASA think, we need to ask the climate itself. It doesn’t matter how small the changes in the Sun are if it turns out that the climate responds strongly to them by causing big changes.

And the best way to find out is to look at what has happened to the climate over the last 11,000 years, the interglacial period we call the Holocene. The advantage of doing this is that the Holocene climate changes could not have been caused by changes in CO₂. They must have been caused by something else.

To study the climate of the past, scientists use various climate proxies that they collect in different parts of the world. A major study published in Science used 73 of these proxies to reconstruct Holocene climate. I have used the same proxies, with a slight modification in the way they are mixed.

What we see, and what a large number of studies also support, is that there was a warm period of thousands of years, called the Climate Optimum, followed by a long period of cooling, called Neoglaciation…

[A]brupt climate events of the past have been studied and identified by paleoclimatologists. Of all of them, we will focus on four of the most important ones. The Boreal Oscillation, the 5.2 kiloyear event, the 2.8 kiloyear event, and the Little Ice Age.

The four are separated by multiples of 2,500 years and form a cycle that I have called the Bray cycle because that was the name of the scientist who discovered it in 1968.

Now that we know the climate of the past, we need to talk about the activity of the Sun in the past.

The Sun’s activity is recorded in the tree rings through the action of cosmic rays. A constant stream of cosmic rays from the galaxy reaches the solar system. Some interact with the atmosphere. Some collide with nitrogen in the atmosphere, converting it to carbon-14, which is heavier than normal carbon-12 and radioactive. This carbon-14 combines with oxygen to form radioactive CO₂, which is breathed by trees…

When we analyze the radiocarbon curve over the last 11,000 years, we observe large deviations that indicate long periods of low solar activity. These extended periods of low solar activity are called grand solar minima and increase carbon-14 production by 2%. The most common ones last about 75 years, and there have been about twenty in the last 11,000 years. The most recent was the Maunder Minimum in the late 17th century. But there are other types of grand solar minima that are much more severe because they last twice as long, about 150 years. The last of these severe solar minima was the Spörer Minimum, which occurred in the 15th and 16th centuries.

There have been only four such Spörer-type grand minima in the entire Holocene. 2,800 years ago, there was the Homer Minimum, 5,200 years ago the Sumerian Minimum, and 10,300 years ago the Boreal Minimum. We know when they occurred thanks to tree rings.

If the dates sound familiar, it is because the four grand Spörer-type Holocene minima coincide exactly with the four major climatic events on the graph we saw earlier. We know that during each of these grand solar minima, when the Sun’s activity dropped for 150 years, the climate experienced a tremendous cooling that had a major effect on climate proxies around the globe.

…Since low solar activity causes cooling, it stands to reason that high activity must cause warming. Solar activity in the 20th century was very high, in the top 10% of the last 11,000 years.

If we count the number of sunspots in each solar cycle over the last 300 years and divide by the length of each cycle, we can see how much solar activity has deviated from the average. Since the Maunder Minimum, during the Little Ice Age, solar activity has been increasing and was well above average between 1933 and 1996, a period of six cycles of increased solar activity that formed the 20th century solar maximum.

Although we cannot know how much of the 20th century warming is due to this modern solar maximum, there is no denying that it is a significant part, because as we have seen, the Sun has been the cause of much of the major climate change over the past 11,000 years.

Conclusions:

There are two pieces of good news. The first is that solar activity cannot rise above the 20th century maximum. It is not like CO₂, which can keep going up. The Sun’s activity can stay high or go down, but it cannot go up, so the warming should not accelerate and should not be dangerous.

In 2016, I developed a model to predict solar activity in the 21st century. At the time, some scientists believed that solar activity would continue to decline until a new grand solar minimum and mini-ice age. But my model predicts that solar activity in the 21st century will be similar to that of the 20th century. It also predicted that the current solar cycle, the 25th, would have more activity than the previous one, and it was right.

The second piece of good news is that if much of the 20th century warming is due to the Sun, then there is no climate emergency. Believing that all climate change is due to our emissions is one of those errors that sometimes occur in science, like believing that the Earth is the center of the solar system, that interplanetary space is full of ether, or that stomach ulcers are caused by stress, not bacteria.

#Sun #SolarActivity #ClimateCrisis #CO2 #ClimateChange #ClimateEmergency