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What
is climate? What is weather?
Climate is a sort of huge 'machine'. What's called
'weather' is just a small bit of this machine which you and I notice: you
know, a tornado,
a  blizzard,
a hurricane ,
very hot weather or very cold weather. And I bet you know what drives this
machine, don't you? Yes, it's the sun. Without the sun, there would be no climate, no weather, no people, no
penguins, no life. So what's the difference between climate
and weather?  This
short video helps explain.
The
climate 'machine'
A tornado is a violent rotating thunderstorm. Wind speeds may reach 300mph in the narrow funnel which descends from the clouds and causes a trail of destruction on the ground. Although tornadoes can happen anywhere, they are commonest in the USA which has a 'tornado season' in early Spring. Most occur in the midwestern and south central states, sometimes called 'tornado alley'.
What are hurricanes? Hurricanes are large rotating storms which bring heavy
rains, floods and winds over 155mph in the worst (category 5) ones. They're
common in the Caribbean region where they occur in a 'season' which peaks
in September. They're also common in other parts of the world wherever there
are warm seas. These storms are also called 'tropical cyclones' or 'typhoons'.
Weather and climateWeather is what happens over days and weeks. It can be hugely
variable, as you know. Climate is the weather averaged over many years.
This can show a pattern, a trend. Over the last century, the trend has been for rising
temperatures and more extreme weather events. This warming trend has been increasing in recent years and is what scientists mean when they speak about 'global warming'.
 The
sun warms the air and hot
air rises bringing with it moisture from the sea. As the moist air rises,
it expands. This makes it cooler and so any moisture in the air condenses
to make clouds.
 And,
as you know, clouds mean rain.
What is condensation?The air in the atmosphere contains water vapour which
you can't see. When the air cools to what is called the dewpoint, the water
vapour becomes tiny droplets of liquid. It's called 'condensation' and can
only take place round 'condensation nuclei', tiny particles such as dust.
As they get carried higher by air currents, the droplets get colder and
absorb still more water from the humid air around them. The droplets get
bigger and it is these that forms clouds which, of course, you can see.
About rainRain drops form as the droplets of water that make clouds continue
to rise higher inside the cloud. They bump into other droplets and become
bigger and bigger. These are now rain drops and are heavy enough to fall
out of the clouds onto you or me.
The sun also warms the seas
and oceans which makes huge currents of water — a little like winds,
but inside the ocean. One of these huge currents is called the  Gulf
Streamin the North Atlantic Ocean. This keeps countries in Northern
Europe warm even though they are nearer the North Pole than the equator.
Another huge current — this time a cold current — affects Chile and Perú
in South America. This is called the Humboldt current. It brings lots of food for fish to eat which once made the
Peruvian fishing industry the biggest in the world. It also means that many
seabirds can live there... including penguins.
All these things — the oceans, the atmosphere, the hot and the cold parts
of the planet, deserts, rainforests — all depend upon climate and
upon the sun.
Why
rainforests are so important
Rainforests like those of the Amazon and
Congo are doubly important. Why? Because they 'make' their own climate.
The trees soak up rain and evaporate moisture through their leaves to form
clouds... you know the rest. They're important for many reasons, one of
which is that if people burn them or cut them all down, the land that's
left is usually poor and the whole climate can change to much hotter and
drier. This could happen within a few years because of all the logging and
burning that people are doing.
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