The Earth has experienced many cycles of climate patterns over billions of years.
We know that weather can change from one day to the next. But climates can change too, over the time span of years, centuries or even longer.
Earth is very old – four and a half billion years old in fact. It can be really hard to get your head around such a big number, especially as humans have only been around for a tiny amount of that time.
That said, I bet you know a bit about how life on Earth has changed. You know about dinosaurs, right? Luckily we don’t need to worry about them anymore! Well, just as types of life on Earth have changed over time, so has the global climate.
So what makes climates naturally change?
Types of life can affect the climate.
When the Earth was very young, even though there wasn’t as much heat coming from the Sun, the planet was very hot and gassy. That’s because there weren’t any plants to absorb these gases. These gases acted a bit like a blanket and stopped the heat escaping – so air temperatures went up.
As life on Earth developed, plants evolved and grew in number. As they were able to absorb gases like carbon dioxide, they helped reduce the blanket effect and temperatures cooled down.
The Sun can affect the climate.
For the last few million years, the sun has been causing climates to change. Stars like the sun get hotter as they age and today the Earth gets more heat from the sun than it did when life was starting to develop on our planet.
The Sun itself is always changing. Giant dark spots called sunspots are always moving across its surface, causing the sun to give off slightly more energy, which makes the Earth a bit warmer.
Earth’s tilt and orbit can affect the climate.
Well, something else that comes in cycles is all to do with the Earth’s orbit – the way it moves around the Sun. The shape of the orbit changes gradually – from a circle to more of an oval – in a cycle that lasts about a hundred thousand years. This makes the Earth move farther away from the Sun at times, so less of the Sun’s energy reaches the planet.
The Earth also tilts as it orbits and that tilt can be bigger at some times than others. This means that parts of the Earth become closer to the sun and so hotter in summer – and others are farther away and so colder in winter.
So naturally there will be cycles of different climates as the Earth’s orbit changes and as the energy the planet gets from the Sun varies, as well as what kind of plants and animals are living. These are all reasons why the climate has naturally changed – and will continue to do so.
But don’t forget – there are things which can affect climates which aren’t related to our orbit of the Sun. Remember the dinosaurs? You’ll probably know that the dinosaurs died out because scientists believe a giant meteorite crashed into the Earth.
The meteorite caused a dust cloud which blocked out the sun causing temperatures to drop. Many living things on Earth died. Something similar happens when volcanos erupt – clouds of ash can fill the skies – sometimes for many years, blocking out sunlight and causing global temperatures to drop.
Scientists have noticed that in the last hundred years or so, the climate has changed in other unexpected ways. Whilst we are in in the middle of a naturally warmer part of the cycle, temperatures have risen much more quickly than they have before.
This is because of the effect that humans have on the environment – and it’s something we’ll be finding out more about next.
You can hear Marina Ventura’s Climate Explorers weekdays from 5pm on Fun Kids!
Get the series on your phone or tablet and listen whenever you like – at home or in the car!
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Marina Ventura’s Climate Explorers with support from the Natural Environment Research Council.