I’m reposting this from Erl Happ’s blog because it deserves wider attention. This is a tour de force, pulling together the different strands of climate knowledge and weather lore Erl has been building up over the years. Hi ideas fit well with those of Marcel Leroux, who worked out that climate change is largely driven by longer term changes in the polar oscillations. Erl believes these are largely due to ozone changes caused by solar variation which drive the global air flows via consequent surface pressure changes. As Hans Jelbring tells us: Wind controls climate. As Nikolov and Zeller tell us, surface pressure and insolation control temperature. Erl delves into the underlying causes of those polar variations, and connects the levels and latitudes of the atmosphere for us in a novel, logical and interesting way.
Climate changes – oh so naturally
Erl Happ Dec 2011
Change in the planetary winds (conceptually documented in the diagram above) is the least remarked but most influential dynamic affecting surface temperature. Wind is a response to pressure differentials. So, a change in the wind is due to a change in these pressure differentials.
The following post describes why pressure differentials and the the planetary winds change over time.
From Wikipedia we have: “the troposphere is the lowest portion of Earth’s atmosphere. It contains approximately 80% of the atmosphere’s mass and 99% of its water vapor and aerosols. The average depth of the troposphere is approximately 17 km (11 mi) in the middle latitudes. It is deeper in the tropical regions, up to 20 km (12 mi), and shallower near the poles, at 7 km (4.3 mi) in summer, and indistinct in winter.”
The notion that there is a tropopause in high latitudes or that it is somehow ‘indistinct in winter’ represents sloppy thinking. At high latitudes, in winter, the air is not heated by the surface (very cold) or the release of latent heat (a cold desert). Neither is it heated directly by the sun (below the horizon). It is heated by the absorption of long wave radiation from the Earth by ozone. In consequence parts of the polar stratosphere and the troposphere are permanently locked together in convection. Consequently ozone descends into the near surface atmosphere. This process changes the distribution of atmospheric mass and therefore surface pressure. It governs the strength of the planetary winds and cloud cover in the troposphere. The process manifests as the Northern Annular Mode (or the Arctic Oscillation) and the Southern Annular Mode. These well recognized modes of inter-annual climate variation affect mid and high latitude temperatures and winter snow cover. But this is not the half of it. The influence of the circulation at the winter pole extends to the equator and the alternate hemisphere, especially in the case of the Arctic where stratospheric ozone concentration is more elevated than over Antarctica. If we imagine that this phenomenon is responsible for just the inter-annual climate variation, we reveal a blindness to the evolutionary nature of the phenomenon and its capacity to change climate over decadal and longer time scales.