Northern Advocate Column

Scientists explain climate change trends

Baring head10 September 2016

On an isolated headland jutting out into Cook Strait there’s a device which has been measuring levels of CO2 in the atmosphere since 1972. This happens to be the longest continuous record in the world.

In 1972 the levels of carbon dioxide were 325 parts per million (ppm). This year they reached 400ppm. The last time they were at this level was 3 million years ago. Global temperatures were then 2-3% warmer and sea levels were 10 metres higher.

This is some of what I learned at a recent lecture held at NorthTec delivered by two climate scientists from Victoria University, Professors Tim Naish and James Renwick. The lecture was one of the last stops on a speaking tour organised by the Royal Society of New Zealand.

That comparison with the world 3 million years ago was certainly meant to make us sit up and take notice. Many of the world’s major cities would be underwater and humans would be clinging to survival in a world of violent weather extremes.

Naish and Renwick carefully explained some of the complex ways that the extra heat generated from carbon emissions is acting on the world’s climate. For instance, 93% of the heat generated since the Industrial Revolution has been absorbed by the ocean. Which is why the increase in atmospheric temperature is thus far limited to 1 degree above the pre-industrial average.

It is the scientist’s belief that significant danger lies somewhere between a 1.5 and 2Cº increase, because that may see the tipping point crossed where the Greenland and Antarctic ice sheets begin an unstoppable slide into the ocean, resulting in a 10 metre jump in sea levels.

To put into perspective the urgency of the problem, global temperature averages are expected to be 1.5Cº hotter within 5-10 years. And if the current rate the world is emitting carbon continues we’ll be looking at a 3.5Cº spike in temperatures, at which point human civilization becomes problematic.

The recent Paris Agreement on climate change saw participating countries agree to limit the temperature increase to well below 2Cº. To achieve this we’ll need to stop using fossil fuels by 2050.

The hopeful message from Naish and Renwick was that if the world acts decisively now we may be able to prevent the worst case scenarios. But even so the latest science is still predicting sea levels to rise by as much as 1.8 metres by 2100, which is going to have a huge impact on global infrastructure and will create hundreds of millions of climate refugees.

For all the worrying facts and figures presented to us, perhaps the most depressing part of the presentation was the acknowledgement that our government is currently doing nothing. While some countries are cutting emissions ours are increasing, with no major policies or initiatives in place to stem the flow.

Where is the government injection of money into public transport and rail? Where is the carbon tax on industrial emissions? Where is the nationwide reforesting of marginal land?

How can we as a country continue to sit aside from one of the most urgent global issues of our time?