Why was summer 2018 so hot??

this video is made possible by brilliant

dog if you live in the northern

hemisphere right now you might have

noticed that it's really rather hot in

the UK we're experiencing a weeks-long

heatwave so severe that when it rained

recently it was greeted with jubilation

in England in Sweden a surge of

wildfires has occurred including more

than a dozen inside the Arctic Circle

where temperatures of topped 30 degrees

and in Japan an unprecedented heat wave

has killed more than 65 people in a

single week it's all but impossible to

sleep horrible to work outside and the

land itself is shriveling up so why is

this happening well as always seems to

be the case there are three main cause

wait no no no no no not yet cause number

one the Atlantic

more specifically the ocean's surface

temperature the surface temperature in

the North Atlantic varies in a complex

fashion every day but underneath that

variability there's a seesaw pattern if

you look at the average monthly

temperature in the Atlantic over several

decades you see this oscillation between

warmer than average and colder than

average temperatures this is called the

Atlantic multidecadal oscillation or amo

and it's caused by the huge ocean

circulation known as the a Mach as well

as surprisingly clouds I'll leave a link

below to a paper if you're interested in

fact every time you see a number on the

screen that's a reference in the

description whether the Atlantic is in a

warm or a cool phase has a huge impact

on parts of the climate like hurricane

formation Arctic sea ice cover and

global temperatures and right now the

amo is in a very positive phase meaning

that the Atlantic is really warm

compared to normal that has a direct

effect on the continents surrounding the

Atlantic with lots more thermal energy

in the northern hemisphere warming

Europe and North America and making

Africa and Europe wetter while making

North America drier wait what the UK

resembles Tatooine right now

incidentally it might like the video I

did about the planets in star wars

well the relationships presented in

these papers show what happens on

average so on average in the past when

the Atlantic has been warmer than normal

Europe has been wetter than normal what

the average response doesn't account for

is the effects of other climate

phenomena and variability on the weather

such as cause number two the jet stream

being particularly weak the jet stream

is a narrow band of fast-moving air that

circles the North Pole

ten kilometers up typically between

about 50 and 60 degrees north it's

caused by the temperature difference

between the pole and the equator

combined with the rotation of the earth

and it's a major factor in what weather

we get in the middle attitudes at the

moment the Jetstream is particularly

weak meaning that the air in the jet is

moving slower than normal or so that the

me and as we see in the jet stream

aren't moving from west to east as fast

as normal because the jet stream marks a

boundary between colder polar air and

warmer temperature if meanders in the

jet stream stay put for a while that

means that regions south of the jet

stream experience warmer than average

temperatures for a long time and

conversely regions north of the jet

experience colder than average

temperatures for a long time the UK and

Scandinavia as well as lots of other

places I didn't mention are all south of

the jet stream and have been for a while

high pressure systems have been sat on

top of these places and refused to budge

that means the colder air and moisture

struggles to get in and alleviate the

hot dry conditions on the flipside

Iceland for example has had its greatest

wettest summer since 1914

that's because Iceland has been on the

other side of the jet stream sitting

further north amongst the persistently

cold temperatures

so Iceland has been cold and wet the

lucky bastard so what caused the jet

stream to be so weak and stationary well

that's quite possibly reason number

three global warming the world is warmer

now than it was before the Industrial

Revolution warming faster than any

natural cycle allows for and that

warming is directly attributable to

human activities notably the release of

gases like carbon dioxide into the

atmosphere there is no debate the

science is unequivocal

if you dispute any of those facts then

you are wrong the globe isn't warming

evenly however due to a phenomenon known

as Arctic amplification the poles are

warming faster than the rest of the

planet which reduces the equator to pole

temperature gradients and because the

jet stream is fed by that temperature

gradient this results in a weaker jet

stream with bigger meanders and the

bigger the meanders in the jet stream

theory tells us that the

more slowly they're gonna move around

the earth so we get persistent weather

patterns like Japan and the UK and

Iceland are experiencing as with all

weather events it is nigh on impossible

to directly attribute a particular event

to global warming these conditions could

well have occurred in an atmosphere

without a single molecule of

anthropogenic origin but what we're

observing at the moment certainly

matches what we would expect to see in a

planet that has undergone global warming

and apart from the weaker Jetstream and

persistent associated high pressure

systems the warming caused by these

local short-term weather systems gets

added on top of the decades-long pattern

of global warming we've seen to give

record temperatures in fact the weak

Jetstream and warm Atlantic also

occurred together in 1976 when the UK

had a record-breaking heat wave which is

now regarded as a yardstick event this

current weather is the most severe heat

wave the UK has seen since then and

monthly average temperatures are higher

in some parts the country now than they

were in 1976 so thanks to global warming

extreme events are getting that bit more

extreme and research indicates that

there'll be more frequent to this summer

in the northern hemisphere is a good

example of what climate change is

probably going to look like this century

when factors come together such as a

warm Atlantic and a wheat jet stream the

additional heat trapped in the Earth's

system by anthropogenic emissions will

take what would have been a big weather

event and make it an extreme one highs

will get higher and as we saw this

winter with the beast from the east you

might want to watch my video about that

the lows will get lower in some places

too but the net effects will be trending

towards a warmer on average climate so

when will this current heat wave end in

the UK well where there's notoriously

difficult to predict long-range

forecasts from the UK Met Office

indicate that the summer isn't going to

cool off significantly by mid to late

August the high pressure system just

isn't budging most likely it's going to

be uncomfortably warm with a few cooler

days until September and then of course

the weather will have to change because

you know seasons but weather prediction

is incredibly difficult especially when

looking more than about a week ahead so

this may well turn out to be wrong for

the time being keep hydrated avoid the

central line check on elderly neighbors

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thanks to brilliant for sponsoring this

video and thank you for watching it I

hope I was able to provide a little bit

more detail than just it was the jet

stream that did it Lowell if you did

enjoy it please do leave a comment down

there in the comments section I would

love to do more videos on atmospheric

topics and I basically I just don't know

if people would watch them it's my forte

it's what I know the most about

I'd like to make more videos about it

but I could do with a bit of feedback on

this so if you enjoyed the video do drop

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see you in the next one thank you again

for watching