date: Mon Dec 1 15:13:50 2008 from: Phil Jones
subject: RE: Fall of temperatures around 1945 to: "Ian Strangeways"
Ian, The Earth's atmosphere system is chaotic. Volcanoes alter circulation oscillations by cooling the surface and warming the stratosphere. The Sun does similar things through variations in cloud around the world. The Sun's output needn't change hardly at all. The various oscillations are know to change and have done since they were discovered. This could be internal dynamics of the climate system, but it is also likely that the major forcing factors are involved as well. If the Sun suddenly increased its output - say by 5%, we all wouldn't get warmer. The atmospheric circulation patterns would change to attempt to still move the heat from the equator to the poles. Most regions would get warmer but some cooler. Cheers Phil
...No the natural factors are the Sun and volcanoes. How these factors influence the SOI, PDO and other oscillations is a factor also. The SOI, PDO and others are natural modes of variability - that the atmosphere likes. Solar changes and volcanoes may push the atmosphere towards one of these modes. Anthropogenic forcing is likely to manifest itself as changes in atmospheric modes...Volcanoes probably affect the year after and the year after that. So for Pinatubo, you'd expect to see the effects in 1992 and 1993 (for a 1991 eruption)...but blaming the changes on an Oscillation doesn't help that much as we've no idea why the oscillation change. See the earlier argument in Q2. [Q] Is proof of CO2 involvement post 1975 derived entirely from models or is there evidence in the actual instrumental data? [Jones] Mostly from models - a la Ch 9 of the IPCC Report.
Hansen et al (2011) write in the abstract, “A recent decrease in ocean heat uptake was caused by a delayed rebound effect from Mount Pinatubo aerosols and a deep prolonged solar minimum.”