The warmers contend that no one studies the role the Sun plays in global warming any more. It is true that measurements of the Sun’s electromagnetic radiation received at the top of the Earth’s atmosphere, hardly changes. There are annual variations in the Sun’s energy received because the Earth’s orbit around the Sun is elliptical rather than circular. We are further away from the Sun in June than in January. However the distance effect averages out as it is essentially the same from year to year.
Sunlight (visible light) is one of the electromagnetic radiations given off by the Sun. In addition to visible light, the Sun’s other principal electromagnetic radiations are infrared and ultraviolet , neither of which is visible.The solar radiation spectrum is shown in the following chart:
The red in the illustration is solar radiation and the yellow areas are illustrative of the absorbing of radiation at certain wavelengths. Oxygen (O2) is absorbing the short wavelength UV, and thereafter, water (H2O) is doing most of the absorbing with only a small amount being done by carbon dioxide(CO2).
Top of the atmosphere total radiation is measured at 1367 watts per square meter. The amount that gets to the Earth’s surface is dependant on a number of things with clouds being the principal factor. However, they can be, at times, overshadowed by emissions from volcanoes for example. According to Wikipedia, the average radiation reaching the surface is about 1120 W/m² . Putting it in terms of energy at Earth’s surface, infrared (above 700 nm) is about52 to 55 percent; visible light (400 to 700 nm) is about 42 to 43 percent and ultraviolet (below 400 nm)” is about 3 to 5 percent. The UV is about 8% at the top of the atmosphere but it is largely absorbed. That results in heating of the stratosphere.
The effect of clouds (cooling) and UV (heating) are considered by many as significant factors. Research on cloud formation due to high-energy gamma rays seeding is being studied. The solar activity clearly has an effect on the amount of gamma rays entering our atmosphere. Thus considerable research into the causes of the increase and decrease of solar activity is taking place. Recently the part played by UV is also getting more attention.
Club du Soleil keeps track of some of the solar research of interest. They post an abstract for the studies they include. Sometimes the link they provide to the study itself will lead to the full study. Other times it will lead you to a site where you will have to pay to see the full study. Look through the listings. It seems most of the studies find that there is a strong correlation between the Sun and climate change. So the warmers contention that no research shows this is merely their way to avoid the obvious. The Club du Soleil posting can be reached by clicking here.
The second abstract “Heartbeat of the Sun from Principal Components Analysis and prediction of solar activity on millennium timescale “ is one I used for a posting several months ago. That authors believe they have discovered the reason for the increase and decrease in solar active over time. They are predicting a “grand minimum occurring in the forthcoming cycles 26-27” by the way.