There have been a number of reports over the past year or two that, taken collectively, seem to point to major changes underway in the Arctic. It's not one thing but a number of changes that are synergistic, each building on the other. These include the rapidly warming Arctic atmosphere and the creation of the more powerful polar jet stream; the loss of Arctic sea ice at rates that were not contemplated even a few years ago; the warming of Arctic Ocean waters, sea level rise and the recent observation of big waves where before there were none; the thawing and burning of the tundra; the exposure and melting of the permafrost beneath; the major increase in wildfires in the northern boreal forests; the spread of black and brown soot from these wildfires and the resultant accelerating deglaciation of the Greenland ice sheet.
We know that the polar jet stream is already playing havoc with us in the temperate zone. It manifests in Rossby waves - deep, slow-moving waves - that can alternately pull warm, southern air into the high northern latitudes and then send cold, Arctic air plunging far into the south. These waves can also leave severe storm events "parked" over certain locations leading to flash flooding of the sort seen in recent years.
What is beginning to emerge from recent observations is that we may have grossly underestimated sea level rise this century especially in the short- and mid-term. By one calculation, all these phenomena playing out today in the Arctic could lead to sea level rise of 2.5-metres by 2040.
I won't explore this forecast in detail. Follow the link, spend an hour or two, and you can come to your own conclusions. Whether 2.5-metres by 2040 is likely, I don't know. What I do know is that we should have very clear answers within 10-years at the outside. We will know by 2025 if this is in store for us by 2040. We might even know by 2020.
What this means is that, by 2020, we may know if we have crossed or are at the tipping point where natural feedback mechanisms, such as those listed above, have carried us into runaway global warming of some extent.
2.5-metres of sea level rise by 2040 wouldn't be the end of Canada or the end of the United States. It would be the end of various low-lying nations. For us, however, it would mean economic upheaval and major social dislocation. It would be an economic body blow. There are a lot of North Americans who live close enough to the sea that 2.5-metres of sea level rise, coupled with the impacts of storm surges, would necessitate retreat from the coast. There are some North American cities such as Miami or New Orleans that cannot survive that sort of rise and would have to be abandoned. The Jersey Shore? Fuggetaboutit.
NOAA has an interactive graphic depicting the impacts of sea level rise up to 2-metres on the United States. It stops at the Canadian border but you can roughly extrapolate from the U.S. picture.
Interesting post Mound.
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