Hat-tip M White.Spaceweather.com has an excellent report today called: ALL-CLEAR IN THE STRATOSPHERE about volcanic aerosols and their impact on the earth’s climate and cooling. Turns out that they have a far greater impact than expected.
Today the earth’s stratosphere is as clean as it’s been in more than 50 years. What does that mean? It means more solar radiation can reach the earth, and is thus contributing to warming. The stratosphere is too clean – because of the lack of volcanic activity over the last 18 years. According to climate scientist Richard Keen of the University of Colorado:
Since 1996, lunar eclipses have been bright, which means the stratosphere is relatively clear of volcanic aerosols. This is the longest period with a clear stratosphere since before 1960.”
Keen examines lunar eclipses and the brightness of the umbra to assess the stratosphere. Here’s how it works:
When the stratosphere is clear, the umbra (and therefore, the eclipsed Moon) is relatively bright. On the other hand, if the atmospheric lens that illuminates the Moon becomes dirty enough, light will be blocked and the eclipse will appear dark.”
A very clean stratosphere leads to warming
Looking at eclipses of the moon allows you to assess the cleanliness of the stratosphere, or its dirtiness, which plays a major role in global temperatures. If the stratosphere is dirty, like after a massive volcanic eruption, then sunlight gets blocked out, and cooling ensues.
But if the stratosphere is too clean, as is often the case after a long period without a major eruption, then the stratosphere becomes clear and thus more sunlight reaches the earth. This results in warming. Well, Keen says there hasn’t been a major eruption since 1992 and so the stratosphere is very clear today, the cleanest it’s been since 1960. That means more radiation – and more warming.
The comparison of images of the 1992 eclipse to 2003 shows that the stratosphere was very dirty in 1992 after the eruption of Pinatubo. In 2003 it was quite clear.
Dr Keen’s presentation
Dr Keen has an excellent presentation up: Volcanoes and Climate Change since 1980. According to the presentation, the earth has warmed about 0.25°C since 1980. The question is why? Keen suggests it’s in large part due to the lack of volcanic eruptions. To find out more, he conducted the lunar aerosol climate experiment (LUNACE).
A lunar eclipse occurs about once a year. By looking at the umbra, scientists can check volcanic impact on the stratosphere every year. Keen provides a historical background on this in Part 3, how it works (Part 4), and calculations (Part 5) in his presentation.
Interesting is that a major eruption that dirties the stratosphere has occurred about every 10 years during the 20th century. The last one was Pinatubo about 18 years ago. So we are a bit overdue now. The stratosphere is much too clean. Too much light is reaching the earth, and so it’s getting warmer.
Keen writes in his presentation:
Since 1997, when Pinatubo’s aerosol settled out, the stratosphere has been exceptionally clear.
In Part 6, Climate) Dr Keen sums it up.
That’s about 0.13°C. Keen writes:
The remaining climate change is presumably caused by other forces, such as solar variability, El Nino, Atlantic AMO warming in 1995, lower Albedo and maybe even a little greenhouse gas.
So many factors out there that get ignored. Looks like it’s back to the drawing board for the climate modellers. A little advice: You’ll never get the models right unless you weight the factors correctly. Start by cutting CO2 by 90% or so. And don’t forget the clouds this time!