You may hear some people say that the greenhouse effect is a natural phenomenon, and the planet has always warmed and cooled and warmed and cooled. And these people aren’t wrong…
The Sun’s energy hits the Earth as visible light, passing through the atmosphere and warming the surface. As the Earth warms it radiates heat back into space.
Carbon dioxide, water vapour, methane, nitrous oxide and other gases (known as the greenhouse gases) in the atmosphere act like a blanket for the Earth, trapping the heat and preventing the Earth from freezing. Pretty neat.
Except, the more greenhouse gases there are in the atmosphere, the more heat gets trapped, warming the Earth more and more, leading to changes in climate.
Since the start of the industrial revolution, us humans have been responsible for pumping more and more greenhouse gases into the atmosphere, accelerating global warming and climate change at an alarming rate. Not neat.
There are a number of greenhouse gases in our atmosphere here on Earth. Each of these gases has an ability to trap heat and warm the Earth but they all do this in differing amounts. To make it easier to measure (we like things we can measure) it was decided to identify how much each of these gases warmed the Earth relative to how much carbon dioxide does.
So each greenhouse gas has its own Global Warming Potential (GWP) which tells you how much it can trap heat and contribute to global warming.
Like Top Trumps. But bad.
GWP is great. Now we know the effect these gases have relative to carbon dioxide we can measure them using one single unit – Carbon Dioxide Equivalent or CO₂e.
You may see this as kilograms or tonnes of CO₂e - kgCO₂e or tCO₂e. So when we talk about reducing carbon emissions, we’re not just talking about carbon but all greenhouse gases.
Net Zero is another term you’ll hear a lot. But what is it? Simply put, it’s the balancing of the carbon books. Whatever emissions we emit, we also have to offset or take out of the atmosphere (think trees or peat bogs or sea grass) with the net result being zero.
Simple…
When governments committed to reaching net zero, a baseline for emissions had to be established. This measurement is used to have a target of emissions which we know we should be able to offset to reach zero. It was decided that if we manage to reduce emissions by 100% from 1990 levels then this should be enough to reach net zero.
So net zero doesn’t mean zero emissions. It just means that we have a good balance. You might hear the phrase nature and climate emergency. This represents the need to make sure we protect our natural environment so that trees do their thing and get rid of all of our carbon for us. Yay trees.