The Vitamin C - common cold nexus is now folklore and as such telling people they are wasting their money is like trying to convert them from one religion to another.

The same can be said for the topical subject of climate change. Our childhood memories of long hot summers, massive floods, raging bushfires etc have been indelibly printed in our brains and now form the yardstick against which everything is judged.

Unfortunately, childhood memories are all too often embellished and exaggerated. Perhaps this is a natural human instinct to make sure we avoid similar experiences again in the natural world where possible. So, it's logical that the average person has trouble accepting the fact that all the scientific evidence is that the climate it is getting hotter, drier and more variable. That's understandable and natural, based on an interaction with the natural world.

But we are now living in a man-made world and the old instincts no longer always apply. In my lifetime CO2 and methane levels have risen dramatically. For well over 100 years we have recognised that these are potent greenhouse gases. I'm now 70 years old and a retired industrial chemist and high school science teacher, among other things.

In my first year of high school in the early 60s we were issued with a brand new text book, the blue Messel which spawned a series of books. As a teacher I taught from that original book as late as the 90s and I know for a fact that it contained a section on the greenhouse effect and the role of increasing CO2 levels. So, if you went to school in NSW and are younger than me you were taught climate change as fact as surely as you were taught the formula for water is H2O.

Let's sort some knowns from unknowns, some certains from uncertains, some possibles from probables then.

We absolutely know that sea levels are rising, temperatures are increasing and weather is becoming more extreme. We measure these things very precisely. When I say we, I mean highly trained and incredibly intelligent scientists that we have invested a fortune in the education and training of, not your old-timer mate down the pub who reckons it was hotter when he was kid. So, we have some knowns that we can absolutely declare as fact.

From here on it gets murkier. We are in possibly the worst drought in history. Is this drought caused exclusively by climate change? Almost certainly not. Has it been made worse by climate change? Almost certainly, but notice my use of the word 'almost'. Ditto the current bushfire situation. It has almost certainly been made worse by climate change but to argue that it and the drought are absolutely, definitely, 100% due entirely to climate change is not a known fact but a distinct probability.

It's a dilemma for the average person. Do we go with our instincts that have served us well for several hundred thousand years in the natural world or do we accept that the agricultural and industrial revolutions and the sheer numbers of humans on the planet have meant that our natural instincts no longer apply in these matters? If our doctor/oncologist, with IQ of 140+, six years of university and many more years medical experience, tells us we have cancer and a lifesaving operation is urgent, do we go home and get our gear and front up to the hospital as advised or do we head to the pub because our old mate knows about an herbal potion that a brother of a friend of his used once?

It's your choice but please choose wisely and be prudent. Err on the side of caution. Remember it's not your health we are dealing with here. It's your children's and grandchildren's. Their textbooks are informing them of the absolute dangers of doing nothing and they'll never forgive you if you stuff it up.

Geoff Richardson

Bellingen