Sound Science Bite: May 14. There has been a lot of press coverage about the polar vortex that plagued the eastern United States and the unusual cold weather that was experienced from the northern plains to the east and south. (At the same time the western US was unusually warm and dry.) One hypothesis that has garnered a lot of attention proposes that the warming of the Arctic and the loss of Arctic sea ice is causing the polar jet stream to slow down and meander, sort of like a mature river such as the Mississippi meanders in its flood plain. Mature rivers meander because their flood plains are broad and have a gentle slopes. The hypothesis draws an analogy to this. The lessened temperature difference between the poles and the lower latitudes means less energy for the jet stream, so it slows down and develops large loops, like river meanders. If you are affected by the part of a loop that is moving air to the north, you experience warmer than normal temperatures. If you are affected by air moving south, it's colder than normal. Additionally, the loops are slow to move (west to east being the usual movement of weather systems in the temperate latitudes), which results in persistent weather patterns - long periods of wet or dry weather, long periods of hot or cold weather.
Not all climatologists agree with this hypothesis by any means, popular in the media though it may be. It is yet to be shown to be valid. Many scientists are worried that, if the hypothesis proves to be incorrect, those who deny climate change is occurring will use this result to denigrate the science of climate and confuse the public. There is a lot of material in this situation to study, not only how science is done and how truth is sorted out, but also how science on the one hand and public policy and opinion on the other play out. Scientists don't really know for sure what will transpire as a result of this global experiment humans are performing on the atmosphere-ocean system. What will happen as the global system warms up so rapidly? Note I write "atmosphere-ocean". One or both are warming. This is something skeptics don't take into account when they point to the steady (but historically very warm) surface temperatures over the past several years. (However, a study published recently in the journal Science has apparently found the "missing" warming.) For example, it remains to be seen how much heat the Pacific Ocean will supply the atmosphere if we have a strong El Nino as expected. The lack of a strong El Nino and the occurrence of La Nina in recent years has meant heat was being stored in the Pacific ocean waters. Scientists are pretty sure that in the long run, global warming very likely will not mean that everybody's temperature rises a few degrees and that's it. What will occur? Wait and see.