Jet stream moved northwards 270 miles in 22 years; climate change to blame?
Climate change is forcing the jet stream higher and closer to the pole in both the Northern and Southern Hemisphere, according research published this April in the journal Geophysical Research Letters. In their paper, "Historical trends in the jet streams", researchers Cristina Archer and Ken Caldeira of Stanford's Carnegie Institution of Washington analyzed data from 1979-2001, and found that the Northern Hemisphere jet stream moved northward at approximately 125 miles per decade (270 miles during the 22-year period of the study). The jet moved higher by 5-23 meters during this period, and the wind speeds decreased by about 1 mph. Archer and Caldeira's study confirms other research showing a poleward movement of the jet stream in recent decades (Fu et al., 2006; Hu and Fu, 2007). All of these changes are consistent with the behavior of the jet stream predicted by global warming theory. For example, Lorenz and DeWeaver (2007) found poleward shifts of the jet stream by 2100 in the forecasts of 15 climate models used to formulate the "official" word on climate, the 2007 Intergovernmental Panel for Climate Change (IPCC) report. However, the authors were careful not to say how much of this shift in the jet stream was due to natural causes versus human-caused climate change. It is unknown if the jet stream has natural decades-long changes in its path that could account for the observed poleward shift.
Figure 1. The jet stream is located where the strongest winds at the top of the troposphere are found (35,000-45,000 feet high, 200-300 mb in pressure).
Archer and Caldeira note that "These changes in jet stream latitude, altitude, and strength have likely affected, and perhaps will continue to affect, the formation and evolution of storms in the mid-latitudes and of hurricanes in the sub-tropical regions." They don't specify what these changes might be. There is very little research that has been done suggesting how changes in the jet stream might affect hurricane formation and strength. One effect we may begin to see in coming decades is a reduction and/or delay in the number of hurricanes that recurve northward out to sea. Recurvature occurs when a hurricane begins to "feel" the westerly winds of the jet stream. As the jet stream continues to move northward and weaken as the globe warms, we can expect that hurricanes moving though the Caribbean will be less likely to recurve, resulting in more hurricane strikes in Mexico and Central America. Unfortunately, the quality of the Atlantic hurricane database for non-U.S. landfalls is not very good, and it will be several decades before we will be able to tell if the number of hurricane landfalls in Mexico and Central America is increasing due to a poleward shift in the jet stream.
References
Fu, Q., C. M. Johanson, J. M. Wallace, and T. Reichler (2006), Enhanced mid-latitude tropospheric warming in satellite measurements, Science, 312, 1179, doi:10.1126/science.1125566.
Hu, Y., and Q. Fu (2007), Observed poleward expansion of the Hadley circulation since 1979, Atmos. Chem. Phys. Disc., 7, 9367.9384.
Lorenz, D. J., and E. T. DeWeaver (2007), Tropopause height and zonal wind response to global warming in the IPCC scenario integrations, J. Geophys. Res., 112, D10119, doi:10.1029/2006JD008087.
Jeff Masters
Reader Comments
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There is weather from central Mexico, all the way down to Columbia, and a large area in the Pacific as well, offshore but connected.
Looks like more than evening showers to me right now.
All will be revealed in the morning I guess.
We just take the systems, re-package them, and send them off to you.
Just trying to please.
Sorry.....
i just saw lighting to my SE
rain is just offshore around mayaro
Anyway, I'm off to bed...see y'all tomorrow...
I'm not sleeping until this thing starts in earnest.....
Stormdude77 is in B'dos, DDR in T&T as well.
Heavy rain here now, real nice.
Will check the site later.
Yes pottery its beginig to fall heavy now
nice!
all this a note
note i will be gone for 4 days i will be going camping starting monday and i be back thursday
but i will be here sat and sunday on the blogs
Say hello to the bugs for me.
I am in south central Mexico and I mean to tell you that we are being pounded. I saw the forecast earlier for "showers" in central/southern Mexico but this is what we would be calling a severe thuderstorm in N. Texas. Downpour and lightening have tapered off but I can hear another round coming in the distance. It has been spectacular.
so for now we this need to keep a eye on it and see how it dos overe night
somebody say something...
Im afraid to PressLord..if you know what i mean....:)
we keep getting wave after wave of lightening storm, heavy rain,m big thunder.
Power, server, signal off and on; I've tried getting through to the weather service but can't and it takes forever to download anything.
Can someone give me a quick pic or idea of what's over us and coming at us?
Thanks-Cuernavaca, Morelos, Mexico 18.92 99.23
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