Guest Post by Willis Eschenbach
Back in 2010, I wrote a post called “Prediction is hard, especially of the future“. It turned out to be the first of a series of posts that I ended up writing on the inability of climate models to successfully replicate the effects of volcanoes. It was an investigation occasioned by the oft-repeated claim from the modelers that the models are wizards at replicating volcanoes, such as this claim from Andrew Lacis:
There we make an actual global climate prediction (global cooling by about 0.5 C 12-18 months following the June 1991 Pinatubo volcanic eruption, followed by a return to the normal rate of global warming after about three years), based on climate model calculations using preliminary estimates of the volcanic aerosol optical depth. These predictions were all confirmed by subsequent measurements of global temperature changes, including the warming of the stratosphere by a couple of degrees due to the volcanic aerosol.
My research showed that contrary to the claims of the modelers, the models did a very poor job of replicating the effect of the volcanoes. In particular, they overestimated the amount of the global temperature change resulting from an eruption. I wrote these and subsequent results up in a number of following articles (list appended). Many people objected strongly to my results that showed the volcanoes didn’t have the huge effect claimed by the models.
As a result, I was pleasantly surprised to find an article in press at JGR entitled “Coupled Model Intercomparison Project 5 (CMIP5) simulations of climate following volcanic eruptions“. The paper is not yet published, but the Abstract says it all:
ABSTRACT (emphasis mine)
• Large volcanic eruptions cause a major dynamical response in the atmosphere
• CMIP5 models are assessed for their ability to simulate this response
• No models in the CMIP5 database sufficiently represent this response
The ability of the climate models submitted to the Coupled Model Intercomparison Project 5 (CMIP5) database to simulate the Northern Hemisphere winter climate following a large tropical volcanic eruption is assessed. When sulfate aerosols are produced by volcanic injections into the tropical stratosphere and spread by the stratospheric circulation, it not only causes globally averaged tropospheric cooling but also a localized heating in the lower stratosphere, which can cause major dynamical feedbacks. Observations show a lower stratospheric and surface response during the following one or two Northern Hemisphere (NH) winters, that resembles the positive phase of the North Atlantic Oscillation (NAO). Simulations from 13 CMIP5 models that represent tropical eruptions in the 19th and 20th century are examined, focusing on the large-scale regional impacts associated with the large-scale circulation during the NH winter season. The models generally fail to capture the NH dynamical response following eruptions. They do not sufficiently simulate the observed post-volcanic strengthened NH polar vortex, positive NAO, or NH Eurasian warming pattern, and they tend to overestimate the cooling in the tropical troposphere. The findings are confirmed by a superposed epoch analysis of the NAO index for each model. The study confirms previous similar evaluations and raises concern for the ability of current climate models to simulate the response of a major mode of global circulation variability to external forcings. This is also of concern for the accuracy of geoengineering modeling studies that assess the atmospheric response to stratosphere-injected particles.
So it turns out to be even worse than I have been saying for a couple of years now. Not one of the models used by the IPCC was able to replicate the effects of volcanoes. The problem, as always, is that the climate is not dead. It actively responds to mitigate and alter the effects of a volcanic eruption, and the models are unable to replicate that active evolution of the global meteorology that occurs in response to the eruption.
It’s always nice to see other scientific studies backing up the results of my own research, particularly when I’ve taken lots of flak for the positions I have espoused. And it’s good to know that once again, WUWT has been publishing tomorrow’s science today …
APPENDIX: My other posts on volcanoes: