“Why the jet stream
buckles violently is not
clear – it may be down
to chaos in the climate”
DISCOVERY OF
THE JET STREAM
lurch north or south; instead, it may be
wandering in tune with natural rhythms
deep inside the Atlantic Ocean.
“A rapid warming of the North Atlantic
Ocean that occurred in the 1990s coincided
with a shift to wetter summers in the UK
and northern Europe and hotter, drier
summers around the Mediterranean. It was
a similar story in 2012 when the UK had
the wettest summer in 100 years,” explains
Rowan Sutton, Director of Climate
Research at Reading University.
This still doesn’t explain why the jet
stream has stuck into such weird contor-
tions in recent years, though according to
Brian Hoskins, the Director of Climate
Science at Imperial, we are seeing the jet
stream buckling into a number of
persistent patterns, different from the
norm. But we can’t tell why yet – and
that could be the most important thing.
It’s tempting to point the finger of blame
at climate change. Jennifer Francis, a
Research Professor at Rutgers University,
New Jersey, has suggested that the
warming Arctic could be to
blame, where the icecap is melting
at an alarming rate. It is creating a
feedback loop that further
increases Arctic temperatures, a
process known as amplification.
However, a warmer Arctic
should make the jet stream
weaker, because there’s less of
a battle between cold and warm air
driving it. There is no clear-cut evidence
that climate change is having much
impact on the jet stream in any other way.
“There’s a lot of misinformation around,”
warns Adam Scaife from the Met Office.
“These are big impacts but no systematic
shift of the jet stream has been found so far,
so it is hard to relate this directly to climate
change. The waviness of the jet stream also
looks variable rather than trending in any
single direction.”
This is a hot topic of research, but itneeds agreement between the computer
models of the world’s climate and real
observations of the weather – only then
can we be confident that the jet stream
is changing, and so far that evidence is
lacking. “The climate computer models
are very successful in spontaneously
reproducing the jet stream and they show
realistic fluctuations from year to year.
But when we add CO2 to the models we
don’t see a big increase in waviness, or a big
increase in storminess like we have had this
winter,” adds Scaife.
However, what is truly exciting is that
we are getting closer to predicting where
the jet stream lies each year, which will
give important clues to the coming seasonal
weather. A recent Met Office forecast for
the North Atlantic is that it is about to cool
and possibly change the jet stream over the
next few years, moving it northwards. In
which case Britain can expect more mild
winters and hotter summers than we’ve had
in recent years.PAUL SIMONS writes the Weather Eye column for
The TimesThe finding that balloons drift
at high altitude was soon put
to an unusual useA Japanese fire balloon - the weapon made its
way to the US from Japan by hitching a ride on
the jet streamThis NASA model of the
polar jet stream reveals its
vast scale and ferocity as
it winds its way over North
America, with stronger
winds shown in redJapanese meteorologist Wasaburo Oishi
discovered the jet stream in the 1920s when
he found that high-flying weather balloons
swept eastwards on strong winds, even in
clear weather. To get maximum publicity he
published his findings in Esperanto, the
international language, but no one read it.
However, when World War II broke out, the
Japanese military realised the jet stream
could float balloons loaded with bombs and
reach America – something no aircraft could
do. The intention was to set fire to the forests
of the western USA and cause mass panic.
But of 9,000 ‘Fu-Gos’ launched only 300
reached America and the forests were too wet
to set alight, although six people in Oregon
were killed by a Fu-Go explosion.