The climate is changing and sea levels are rising, undermining our long-held ideas about where we can live, where and what we grow and farm, and how we operate as a society and a culture.
How is this happening and what can we do about it?
The earth’s climate is governed by a balance between the amount of energy coming in and the amount going out. All that energy comes originally from the sun, so the brightness of the sun is one of the key factors in defining the climate, but not the only one. The other key one is the composition of the air, the atmosphere.
Because the earth is warmed by the sun, it radiates heat energy back to space. Some of the gases in the air are really good at soaking up heat the earth radiates, then sending some of it back down to keep us warmer – just like a duvet is good at soaking up our body heat, keeping us warmer in bed. The thicker the duvet, the warmer we are; the more of those “greenhouse” gases in the air, the warmer we all are.
Humans have become really good at putting greenhouse gases in the air since we discovered the potential of coal and oil to power our lives. This would all be fine if what goes up comes down again quickly. Some greenhouse gases are like that, but carbon dioxide isn’t. It stays in the air for centuries and builds up over time. Since we started burning coal, the amount of carbon dioxide in the air has gone up over 40 percent, a change the earth alone might take a million years to achieve.
So the world is getting warmer, and the cold bits are melting. Right now is the warmest the world has been for more than 1000 years. Hot days are more common and extreme floods are happening more often (since warmer air contains more moisture). Two degrees of warming would see a tripling of the number of droughts and wildfires in the already-dry eastern parts of New Zealand, as well as big increases in the occurrence and severity of floods. The Fox and Franz Josef glaciers would be only stories to our grandchildren.
For the first time in thousands of years, the oceans are rising. Less than 30cm so far, but we’ll see that much again in the next 40 years when we could be in for a lot more. If warming goes much beyond two degrees, we’ll likely see large parts of the Antarctic and Greenland ice sheets melt away, with 10m or more of sea level rise over centuries, enough to inundate millions of people and to change coastlines around the world.
That’s why the Paris Agreement on climate is so important, getting the world on track to keep warming well below two degrees. How do we do it? By stopping our release of greenhouse gases. How soon do we have to stop emitting? Soon.
At present rates, within 20 years the world will have added enough carbon dioxide to reach two degrees of warming. Getting on a downward path no later than 2020 and getting to zero around 2050 or soon after is what we need to do. A big ask, but it can be done. Every country needs to get to zero emissions, including New Zealand, where emissions per capita are in the top 10 globally.
As individuals, we can make more use of our public transport networks, reduce the amount we throw away, and move to low-energy light bulbs, among many other things. As a nation, we can promote electric vehicles, get to 100 percent renewable electricity, boost public transport, find lower-carbon farming solutions and invest in green technology.
In order to achieve these goals, we also have to develop – and practise – ways of exploring how the changing climate is going to impact our lives, sectors and communities. As well as learning about what’s coming our way, we have to identify how we can change our lives and the way we live – including the systems and rules that run this country – so a sustainable future is both achievable and something to look forward to.
We could be global leaders – if any country can do it, surely New Zealand can.
Professor James Renwick and Dr Rhian Salmon will be expanding on the themes of this article in ‘Climate change: What’s coming our way?’, 11.30am–12.30pm, Thursday 15 February, Lecture Theatre 2, Government Buildings, Pipitea Campus, 55 Lambton Quay, as part of Victoria University of Wellington’s free Spotlight Lecture Series. Register here.