Climate change 101

02:27, Mar 03 2014

February focus: climate change

Challenge: only use my car once per week

OPINION: I find global warming hard to get my head around. A blanket of carbon dioxide and methane and other gases, woven by human activities, that swaddles the earth and is heating things up. Say what? If you can picture that you've got a first-rate imagination.

Not that there's anything imaginary about climate change. Although for the past two decades it's been tricky for us non-scientists to know what to believe. Hasn't the world always experienced naturally occurring cyclical weather patterns and isn't this just another one of them? The skeptics were loud for a very long time. They've got a bit quieter now.

"It is extremely likely that human influence has been the dominant cause of the observed warming since the mid-20th century," confirmed the Intergovernmental Panel on Climate Change [IPCC] last year. At a do at Buckingham Palace, Prince Charles recently went as far as to call climate change sceptics the "headless chicken brigade"

You know you're on the wrong side of the mild-mannered prince when he calls you a headless chicken.


Scientists are now as sure that humans are the main cause of modern climate change as they are that smoking causes cancer. When the IPCC says "extremely likely", what they technically mean is that the scientific experts are more than 95% certain in their conclusion. It's actually extremely rare for scientists to agree that closely on anything - science thrives on disagreement.

How well do you feel you understand the science of climate change? Let's go back to basics for a minute. Greenhouse gas emissions are mostly produced by the burning of fossil fuels (coal, oil, gas) for electricity and industrial production, heating and transport. We're talking about the fuel needed to keep factories churning out our cans of baked beans, BMWs, or Barbie dolls. The petrol we put in our cars. The fuel that makes aeroplanes fly. The burning of these fossil fuels releases carbon dioxide into the atmosphere, the world's main greenhouse gas.

The world's second main greenhouse gas is methane, produced mostly by the agriculture industry. Methane is the gas released when cows and sheep belch and fart. "Hey but isn't that perfectly natural?" you might ask. Sure, but given the numbers of cows being farmed for meat and dairy that's a whole lot more bovine belching and farting going on in the world.

Deforestation is another cause of greenhouse gas emissions. Trees absorb and store carbon dioxide, but when they are cut down and burned, this carbon dioxide is released. Cutting down trees also means they will no longer be able to act as carbon dioxide inhalers for us in the future. Other greenhouse gases include nitrous oxide, HFCs and ozone. The places they come from include agricultural fertilisers, spray cans and our refrigeration systems.

In short, a whole bunch of human activities has led to an increase of these greenhouse gases. Greenhouse gases emissions rise up into the atmosphere, forming a kind of invisible blanket that surrounds our planet. They let the sun rays shine in, but absorb some of the heat radiating back from the Earth's surface before it escapes to space. Hence the idea of a metaphorical greenhouse that the earth is beginning to bake within.

If you're more of an audio visual type, this clip gives a good explanation of how climate change works. 

In New Zealand, most of our greenhouse gases are produced by the agriculture sector (47.2 per cent) and the energy sector (42.6 per cent). The remaining are produced through industrial processes (7.5 per cent) and waste (2.7 per cent).

One of the things I most wanted to know at the start of my month looking at climate change was how New Zealand was doing in terms of reducing our greenhouse gas emissions. Unfortunately the answer is not pretty. More on that in my next blog.

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