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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456, Thanks for the explanation. I can see I'm going to have to start observing the south. hem., to begin to understand the northern one.
I thought all this would get easier with time............But.........
The Southern affects the Northern Hemisphere and especially if those effects are wind surges. Wind surges from the Southern Hemipshere increase the liklihood of tropical cyclone formation in the Northern Hemisphere. For example, one factor that played a role in the cyclogenesis of TS Alma (other than MJO, TWave influences) was a surge of southerly winds from the South Pacific High.
LOL
/i'm starting to resent surfboards! LOL
An interesting wave off Africa again it seems. This one has some peculiarities, according to the Discussion at about 5:pm. Have not checked it since then.
Also...its late next week which is pretty far out and unreliable. For all we know, the GFS could drop that area between now and Monday. Maybe 72 hrs, when confidence is high.
I'd say this year seems to be one where a June storm might be likely, except for that very low ITCZ.
Nobody responded to that question about why it's so low in the ATL, did they? My theory is that it is being affected by the far southeastern position of the AB high. Any other possibilities?
Post 323.
Ah.... back to tropics.... Yay! No more GW. No more CC. No more IQ and age. Just plain old, everyday, run-of-the-mill, ordinary, more-of-the-usual stuff tropics... Ok, ok. I admit... I took that one a little far.
I was trying to deviate from the current subject. I assume it worked...
I haven't seen the sun set in a while =P lol it rains everyday =( But oh well I guess its better to get rain that to not get any =)
It has been raining almost all June =( But I guess the plants needed a little bit of H2O =)
should bring us some much needed rain fall on saturday if it holds its present speed and convection.
Maybe it will rain tonight...........
See you all tomorow
I need to get early tomorrow
Good Night!
I believe the crownweather.com would agree with you as well.
Storm capable of producing a tornado
Tornado Vortex Signature (EAX_O7)
ID: O7
County: Platte
Max: 62 dBZ
Top: 40,000 ft.
VIL: 66 kg/mē
Chance of Severe Hail: 50%
Chance of Hail: 100%
Max Hail Size: 1.25 in.
Speed: 47 knots
Direction (from): SW (220)
WWJP25 Weather Chart
09:00 AM JST June 6 2008
Subject: Tropical Depression in seas south of Okinawa
At 0:00 AM UTC, Tropical Depression (1006 hPa) located near 24.5N 122.3E has 10 minute sustained winds of 30 knots with gusts up to 45 knots. The depression is reported moving north-northeast slowly.
MSGID/GENADMIN/NAVPACMETOCCEN PEARL HARBOR HI/JTWC//
SUBJ/TROPICAL CYCLONE FORMATION ALERT//
REF/A/RMG/NAVPACMETOCCEN PEARL HARBOR HI/050121Z JUN 08//
AMPN/REF IS TROPICAL CYCLONE FORMATION ALERT (WTIO21 PGTW 050130)//
RMKS/ Link
(Florida needs a good soaking.)
Tomorrow another day of watching what little showers the seabreeze kicks up depart to the West. Wait! Come back rain!
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