The familiar global weather patterns that we, our parents, and our grandparents (and most of our distant ancestors, at least as far back as the last ice age remnants) have always experienced are no more. We have entered an abrupt climate change phase in which an energized water primed atmosphere and disrupted circulation patterns give rise to unfamiliar, massive and powerfully destructive storms, torrential rains, widespread heat waves and droughts, and less commonly but occasionally widespread cold spells.
Why is this happening now? Sophisticated Earth System computer Models (ESMs), summaries of state-of-the-art peer reviewed climate science (Intergovernmental Panel on Climate Change IPCC), and mainstream science have generally put the climate change threat out to the latter part of the century. Global data from all parts of the world, but most noticeably the Arctic shows that reality is quite different from these models and mainstream thinking.
Just by looking out the window much of humanity now senses that something is very different, and uncomfortably wrong in their particular region.
Depending on location, vegetation is drying out and burning, or being toppled by very high wind events, or oceans are invading upon coastlines, or rivers are overrunning banks or drying up or both, while rainfall deluges are inundating other regions. In fact some regions are vacillating between massive floods and massive droughts, or record high temperatures and record low temperatures, even on a weekly basis.
As crazy as things are now, clearly they are not bad enough to wake up the general population enough to vote down denier politicians and demand extensive governmental action on the problem. Not to worry, that action is a sure bet in the near future, the only question is will it happen next year, or in 3 years?
In the meantime, many of us are doing as much as we can to educate people on the dangers we face and speed up the understanding of climate reality process. As much as we do, ultimately it is the hammer of extreme weather, causing, for example global crop failures or taking out a few more cities in rich countries that will take the final credit for an abrupt tipping point in human behavior.
The key to the disruption in the climate system is the Arctic
Human emissions have inexorably increased levels of carbon dioxide and methane (Greenhouse gases GHGs) in the atmosphere sufficiently to cause an incremental overall increase of global mean surface temperature by 0.8 degrees C over the last century. Over the last 3 decades, the GHGs have caused sufficient warming in the Arctic to melt enough land-covered snow and ocean covered ice such that the highly reflective surfaces have been replaced by dark underlying land and ocean greatly increasing sunlight absorption causing Arctic temperature amplification of 3x to 5x and higher.
This has melted permafrost on the land and on the shallow continental shelves and has increased Arctic methane emissions, which on a molecule-to-molecule basis cause warming >150x compared to carbon dioxide on a short timescale. Arctic temperature amplification has reduced the equator-to-Arctic temperature difference, which is responsible for setting up global circulation patterns on the rotating Earth. Thus, the high speed jet stream winds which circumvent the globe become slower, and wavier, and weather patterns change.
Extreme weather events become stronger, more frequent, of longer duration, and act on new regions. In effect, the climate background has changed, so the statistics of all weather events changes. When the ocean tide comes in all boats rise, when the climate system changes all weather events change.
So how does the North American freeze of early January, 2014 and the upcoming late January, 2014 freeze fit into this picture? In our familiar climate, the polar jet stream flowed mostly west to east (with small north-south deviations or waves, with typically 4 to 7 crests and troughs around the globe) separating cold dry Arctic air from lower latitude warmer moist air. The latitude of the jet moves southward in our winter and northward in our summer.
In our present climate the jet stream waviness has greatly increased and eastward average speed has decreased. Not only that, but in early January there were only two troughs (over North America and central Asia) and two crests (over Europe and the Pacific up through Alaska and the Bering Strait).
The troughs had temperatures 20 degrees C cooler than normal, while the crests had temperatures 20 degrees C warmer than normal. These large waves and slowing of the jet stream is directly responsible for the changes we have been experiencing in weather extremes. Cold or warm, depending on your location.