Climate change: frequently asked questions

A UN team of climate scientists predicts a dire future, including rising seas and temperatures. Environment reporter ANNE BESTON examines its report.

First, the jargon: what are the greenhouse effect and global warming, and why do scientists go on about fossil fuels?


Gases occurring naturally in the atmosphere form a "blanket" around the Earth, trapping warmth from the Sun so we do not freeze to death, as we would if we lived on Mars.

These gases, mainly carbon dioxide (CO2) but also methane and nitrous oxide, are increasing because of human activities. The blanket is becoming thicker, and too much warmth is getting trapped.

We produce greenhouse gases when we burn fossil fuels - coal, oil, gas - which produce CO2, as do cars.

The other problem gas is methane, and in New Zealand we produce lots. Farm animals emit methane when they digest grass. Chopping down trees, or deforestation, is another contributor because forests soak up CO2.

Climate change, global warming, the greenhouse effect - basically they all mean the same- the Earth is getting warmer.

So what?


If the Earth heats up as much as predicted - the latest gloomy scenario is a warming rate of 6 degrees over the next 100 years - we could be in for a very bad time indeed.

Extreme weather, more rain and flooding, island nations swallowed by the ocean as the icecap melts and sea levels rise. The disappearance of thousands of plants and animals.

The weather would change. Dunedin could get Auckland's climate, while Auckland could become more like Suva. The average daily maximum in Dunedin is 20.6 degrees, in Auckland it is 23.5, and in Suva 31.7.

(Adding the full predicted 6 degrees is misleading, however, because colder areas are likely to warm at a lesser rate than hot ones.)

Who says all this and how do they know?


The latest predictions come from the International Panel on Climate Change (IPCC). It is a United Nations team of 150 climate scientists from more than 100 countries, including five from New Zealand.

Their work was reviewed by 500 other scientists.

They collect data in their own countries, then collate it into a report every six years or so.

CO2, for instance, is measured all over the world - we do it on the south coast of Wellington during a fresh southerly to get consistent samples. Scientists also look at tree rings, the marine environment and icecaps to get a picture of the world's past climate.

One way to measure historic CO2 levels is to take a thin "core" of ice from a sheet that formed 150,000 years ago and analyse the air bubbles trapped in it. The bubbles have less CO2 than ones formed more recently.

What did did the latest report say?


That the Earth is warming at twice the rate previously thought. It blames humans for the warming over the past 50 years.

It predicts that the Earth's temperature will increase by 6 degrees by 2100 and picks that sea levels will rise almost 1m. It says snow cover on lakes and rivers in the Northern Hemisphere has reduced by 10 per cent since the 1960s and that the Arctic sea ice has decreased in thickness by 40 per cent.

CO2 in the atmosphere has increased by a third since 1750.

It's hard getting an accurate forecast for the weekend - how do these guys think they can predict the weather in 100 years?


Scientists say the report is based on averages and explain it like this: if someone wanted to predict the average daily temperature for Auckland for next summer, it is likely he would be out by no more than about 1 degree after looking at averages over past decades.

Scientists use the same kind of data when predicting the Earth's future climate. Predicting the weather for Christmas Day 2100 might be a bit tougher, however.

Is New Zealand better off than the rest of the world?

Yes and no. Yes because as a country surrounded by ocean, which helps cool the atmosphere, we are unlikely to suffer the upper limits of warming predicted. Instead, we would probably get 60 per cent of the upper prediction, an increase of say 4 degrees instead of 5.8.

But that same ocean is predicted to rise as much as 88cm by 2100, not good news if you own a waterfront beach-house.

What can we do and are we doing it?


New Zealand is a party to the Kyoto Protocol, as are 84 other states. The protocol is only a stepping stone to agreement on each country reducing greenhouse gas emissions.

The process is complicated, but this is how it will work for New Zealand:

If we agree to reduce our emissions by a set amount (our target is to get greenhouse gas emissions below the level they were in 1990), we "ratify" or sign up to the protocol.

Someone will come and check our progress in 2005, and the hard work begins in 2008. The Government is drawing up policies to achieve our targets, but Parliament will then have to legislate.

But surely we're not a major culprit, because we're so small?


For only 3.8 million people, our production of greenhouse gases per head is quite high. That is because the measurement is done per human head - sheep don't count.

New Zealanders produce about 8000kg a head a year of greenhouse gases - the global average is 5000kg. It is methane that puts our per capita level up - all those flatulent sheep.

Why doesn't everyone just get on with it then?

Because there is an awful lot of arguing going on. Even if we did our bit, plenty of countries are refusing to commit themselves.

For instance, the United States and some European countries locked horns at the last round of talks held in the Hague in November over CO2 reduction.

The United States argued that CO2 absorbed by forests and farmland should be subtracted from a country's reduction quota. The meeting was suspended and is due to resume in Bonn in mid-year.

Isn't the Kyoto Protocol a waste of time?


The protocol is actually an innovative process - for instance countries that do very well in meeting their targets will get "emission credits." A country like New Zealand could then buy those credits to keep within our targets.

Credits could be traded on international commodity markets, just like oil or money. Credits could also be traded domestically between companies in New Zealand.

Dr David Wratt, of the National Institute of Water and Atmospheric Research in Wellington, said yesterday that it was hard to imagine CO2 levels would not rise to 500 parts per million anyway, no matter what happens with the protocol.

Now they are about 350 ppm.

Kyoto may not be the magic bullet, but so far it's all we've got.

Could 600 international scientists be wrong?


Possibly. The greenhouse debate has hatched a new fad term - "climate sceptic."

Some scientists, including Dr Chris De Freitas, of Auckland University, question the science of global warming.

Some of the sceptics point out that sea levels around the tiny South Pacific island of Kiribati have actually dropped. This is in direct contrast to what the climate scientists say, which is that as sea levels rise, Kiribati, just 2m above sea level, will be swallowed by the ocean.

Dr Wratt replies that oceans are like a big bath - their level changes constantly as water swooshes around the globe affected by weather patterns.

But in the long term, the average sea level is rising.

Herald Online feature: Climate change

Intergovernmental Panel on Climate Change

* Draft summary: Climate Change 2001

  (requires Adobe Acrobat Reader)

United Nations Environment Program

World Meteorological Organisation

Framework Convention on Climate Change