Weather Watch: Climate change slow, but real phenomenon

Evidence of global warming is everywhere. Photo / AP

"So much for global warming." That's quite possibly one of the most common phrases I hear every time New Zealand has a cold snap. It's understandable people are confused by scientists telling us the world is heating up and to prepare for the worst, only to then be told August was the coldest on record.

However, there is a huge difference between what is gradually happening over a century, and the usual weather we'll continue to receive over the next few decades.

From the scientists I've spoken to, it sounds as though New Zealand will be one of the better-placed nations to cope with and adapt to climate change. Some suggest we will become a warmer, tropical paradise that could see grapes grown across Waikato and Northland and a climate that has mild winters and hot, humid summers.

But we're talking decades for this to happen, perhaps more than 100 years.

"Climate change is about a gradual shift in average conditions underlying the usual variations in the weather," says Dr James Renwick, associate professor at Victoria University's School of Geography, Environment and Earth Sciences.

He says we will still get occasional cold snaps as well as heat waves as the climate warms but the chances of getting very cold spells will gradually decrease while the chances of getting the warm spells will gradually increase.

"Imagine we draw a card at random from a pack of playing cards. When we use the full pack, we have a 50:50 chance of drawing a red card. But, if we start taking out the black cards, our chances of drawing a red card will go up. Gradually removing the black cards is like gradually warming the average climate: the chance of drawing a red card (or a warm year) goes up over time while the chance of drawing a black card (a cold year) goes down."

So my generation may not really witness significant climate change. It's a bit like the ageing process - one day you look in the mirror and notice things have, well, really changed.

Renwick says atmospheric carbon dioxide concentrations are almost at 400 parts per million, and the evidence of warming in the atmosphere, the oceans, and the ice sheets continues to mount. "We will always experience the ups and downs of the weather, but the climate is clearly changing around us."