Wondering Willis Eschenbach makes more mischief with volcanoes

Wondering Willis Eschenbach has a well-earned reputation for wandering off on a tangent and avoiding scientific research. He's done the same today at WUWT (archived here, latest here). He decided that two recent papers relating to volcanic forcing are "wrong". Not because he took any notice of the content of the papers - he didn't. Not because he took any notice of the observations reported. He didn't. He decided to reject the months of hard work by multiple scientists, on the basis of his own five minutes of "research".

Climate models and volcanic forcing

The two papers found evidence of volcanic forcing, coming from two different perspectives:

• Observed increase in Stratospheric Aerosol Optical Depth (SAOD) since 2005 (Ridley14)
• Multiple signals of volcanic forcing in sea surface temperature, atmospheric water vapour,  net clear-sky short-wave radiation, and elsewhere (Santer14)

One of the main points the scientists emphasised was that the CMIP5 models mostly assumed there was zero change in stratospheric volcanic forcing after 2000. They show that this assumption is not valid. Since 2005 in particular, there has been significant volcanic forcing, based on observations.

Smaller volcanic eruptions helped slow warming, but deniers at WUWT don't believe it

There was a paper that came out last week that you might have heard about. It was by David Ridley from MIT and a team of others, including some very high profile scientists. What they did was investigate the impact of volcanoes over the past few years. They found that the cooling effect of volcanoes since 2000 could be from 0.05°C up to as much as 0.12 °C, which would be quite a bit more than previously thought.

The Sarychev Peak Volcano, on Matua Island, erupted on June 12, 2009.
Credit: NASA via AGU

There have been other recent studies looking at the impact of volcanoes, including by some of the co-authors of this paper. I've written previously about the article by Gavin Schmidt, Drew Shindell and Kostas Tsigaridis,  in a special edition of Nature Geoscience, "Focus on recent slowdown in global warming". That issue also had an article on volcanoes, two of whose co-authors were also co-authors on the Ridley paper.

This new work was different.

What this team did was look particularly at the impact of volcanic aerosols in the stratosphere below 15 km. From satellite observations, scientists know that above 15 km, volcanic eruptions that are smallish in size can perturb incoming solar radiation. David Ridley found that below 15 km in the stratosphere, there has also been a measurable impact by volcanoes.