Hasn’t the climate always changed?

Our planet earth is about 4.5 billion years old, and it’s climate has changed many times. Scientists study ice cores, ocean sediments and tree rings to understand past climatic changes. But what we’re witnessing now is a very rapid change – around 10 times faster than any climate changes in earth’s history.

What is causing it? (Warning: science ahead!)

Earth’s atmosphere is made up of various gases – mostly Nitrogen (N2) & Oxygen (O2), plus a very small % of ‘greenhouse gases’ (GHGs): Carbon dioxide (CO2), water vapor (H2O), methane (CH4), nitrous oxide (N2O).
The sun emits shortwave radiation (visible light) which passes through these gases to the Earth’s surface (land + water). This warms the Earth, which then radiates out longer wave infrared energy or heat. Heat passes through the simple, tightly bound molecules of N2 + O2.
However, the 3 or 4 atom molecules of the GHGs, are loose enough to vibrate when they receive heat energy. The vibrating molecules re-radiate the energy out in all directions – either to other GHG molecules or back to Earth. This is what keeps Earth warm
The composition of our atmosphere is what maintains life on Earth as we know it. Our Moon has no atmosphere + is approx 127 degrees C where the sun shines and -173 C in shade. GHGs play a very important role in re-radiating just the right amount of heat back to Earth.
The problem is we’re adding too much of the GHGs (mainly CO2 + CH4) to the atmosphere which are re-radiating long wave energy back to Earth, warming the oceans + land more than usual.

What have fossil fuels got to do with it?

Fossil fuels (coal, oil & gas) come from remains of plants & organic matter fossilised millions of years ago. They are rich sources of carbon.
Burning fossil fuels creates carbon dioxide (CO2). Since the 1850s, the amount of fossil fuels burnt has increased rapidly, causing a massive rise in CO2 levels in our atmosphere. The increased CO2 has trapped more heat than normal. Scientists know that over the past 400,000 years, CO2 has been between roughly 180 – 280 parts per million of our atmosphere. But the past 70 years or so it has gone up dramatically and is now > 410 ppm.

graph via NASA

What can we do?

Basically, stop using fossil fuels and clearing forests!

More info coming ….

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