Climate change 101: The most important things to understand about this urgent problem

Wednesday, 28 November 2018

Tackling climate change is seen by many as the most urgent goal of this generation.

For many, tackling climate change is the ultimate responsibility of our time – working out how to stop the planet warming up so much and so quickly that it causes irrevocable damage that humanity is ill-prepared to cope with.

But for the average person, it can be hard to decipher what it all means, how it will affect us and, crucially, whether we can do anything about it.

A key step is understanding the basics of climate change itself, a term used to explain the consequences of our warming planet.

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WHY IS THE PLANET WARMING?

Earth's warming is largely related to the quantity of greenhouse gases in the atmosphere.

Victoria University lecturer and climate change expert Professor James Renwick believes individuals must hold their government to account.

These absorb heat from the sun as it is reflected off the earth's surface and send it back again.

Professor James Renwick, a climate scientist at Victoria University Wellington, says this process is akin to having a blanket on a bed.

'A thicker blanket, a warmer body; a thicker blanket over the earth, a warmer earth.'

Cows are responsible for about half of New Zealand's greenhouse gas emissions, compared with 10 per cent in most other countries.

The key thread in that blanket is carbon dioxide (CO₂), which takes thousands of years to break down and all the while absorbs heat, sending it back to earth and triggering warming.

HOW IS IT OUR FAULT?

Humanity has played a major part in the abundance of CO₂.

Since the start of the industrial revolution around 250 years ago, emissions of CO₂ have sharply increased. This is largely because we've used an increasing amount of fossil fuels like coal and oil in order to fuel cars, trucks, planes and trains – and to heat our homes and workplaces. When those fossils fuels are burned, they release CO₂ into the atmosphere.

New Zealand is in the top 10 countries per head of population for emissions, Renwick says. We rank similar to the US and Australia and ahead of China.

WHY ARE OUR COWS BLAMED?

Melting ice in Antarctica is helping to contribute to rising sea levels, one of the critical challenges countries will face over the next century.

Methane and nitrous oxide, like carbon dioxide, are greenhouse gases that absorb heat.

Unfortunately for New Zealand, cows – especially dairy cows – produce a lot of both methane and nitrous oxide. They do this by burping out methane and peeing out nitrogen, a tiny proportion of which emits nitrous oxide.

There are also a lot more of them than before. Between 1995 and 2015 dairy cattle increased from 3.84 million to 6.49m.

In 2015 there were 1,254,000 dairy cattle in Canterbury alone, a staggering rise of 490 per cent from the number in 1994.

New Zealand's farmers are among the most productive and efficient in the world, improving the emissions efficiency of production by about one per cent a year over the last two decades.

Cyclones battered the West Coast earlier this year, triggering fresh fears about coastal erosion from sea level rise. Hector resident Brent Dyhrberg was among those left wondering what the future holds.

But agriculture still accounts for almost half of our greenhouse gas emissions, compared with around 10 per cent on average globally.

WHAT IS IT DOING TO OUR CLIMATE?

In New Zealand, temperatures have increased by about 1 degree Celsius over the last century.

One consequence of that is more frequent extreme weather.

Rising temperatures mean more very warm days, leading to more frequent heatwaves.

Water evaporates faster, which makes drought more likely but also leaves more moisture in the air, leading to heavier rains and greater potential for flooding.

Franz Josef Glacier is also melting at an alarming rate, so much so that visitors are now no longer able to walk onto it, its face dangerously unstable.

'Last summer was a great example,' Renwick says. 'We had the warmest summer on record in New Zealand, we had extreme heavy rainfall, very dry conditions in places and we felt the effects of two or three ex-tropical cyclones that passed over the country.'

AND WHY IS THE SEA RISING?

Then there are rising sea levels. The heat coming back from the CO₂ blanket is absorbed by the ocean, which makes it expand. Melting glaciers and the huge Antarctic and Greenland ice sheets add to the problem.

The ramifications are sobering – estimates for seas rising around New Zealand range from 30cm to one metre by 2100, putting more than 130,000 people at risk.

THE OTHER PROBLEMS

In warmer temperatures and drought conditions, some crops will no longer grow where they could before. This means malnutrition and starvation for many people.

Captain Planet is an example to all of us. The climate change crisis will not be addressed without people taking action.

Coastal erosion caused by rising sea levels will create large numbers of people in need of a new place to live. Those who lack the economic means to do so may suffer severe hardship.

The changed climate also messes with the eco-systems that sustain life. Biodiversity will suffer as creatures are unable to evolve with the rapid changes to their habitats.

THE WORK TO SAVE THE PLANET

There is global urgency to keep temperature rises to below 2C and preferably no more than 1.5C above pre-industrial levels, a limit that would substantially reduce the risks and effects of climate change.

To do so is a monumental task.

'At the present rate of emissions globally we will have put enough CO₂ in the atmosphere to guarantee 1.5C of warming within 10 years from now, and 2C of warming within 20 years,' Renwick says.

The need for action is critical, and the necessary goals are getting harder to reach. Last month a landmark global report on limiting global warming to 1.5C found it would require 'rapid, far-reaching and unprecedented changes in all aspects of society'.

And just this week, the United Nations found the world is well off course on its promises to cut emissions and may have even farther to go than previously thought.

But there is hope. Key to New Zealand's efforts is the Zero Carbon Act, which would commit the country to zero carbon emissions by 2050 or sooner.

WHAT YOU CAN DO

To turn around global emissions requires everyone to play their part.

'The best thing individuals can do is work to hold the government to account,' Renwick says.

'Make sure you let your MP know you want to see this happen and make sure your family and workmates know that climate change is a big deal.

'Use less energy, make sure your house is insulated, take the bus instead of the car - those sorts of obvious things. If it's a nationwide effort then it does make a difference.

'It's really important for the citizens of this country to know these things, because it's going to shape all our lives in the future.'

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