When we talk about the future, we often talk about climate change.
On this page:
In the last few years, we’ve been hearing a lot about climate change. We read about it in the news and on social media. When we talk about the future, we often talk about climate change. You might have even been to a school protest about climate change, alongside hundreds of thousands of other young New Zealanders.
Climate change is the phrase used to describe the long-term warming of the planet and increase in extreme weather, caused by increasing amounts of greenhouse gases in the air. Our understanding of climate change is based on more than 50 years of scientific studies from all around the world. While there have been periods of natural cooling and warming throughout the Earth’s history – ice ages, for example – the Earth’s climate is warming faster than ever before. In this lesson, we’ll explore the science behind climate change, greenhouse gases and the impacts climate change will have on the world and New Zealand specifically.
Before we learn about greenhouse gases and the greenhouse effect, it is helpful to know a bit about the Earth’s atmosphere and how it works.
The atmosphere is the layer of gases (known together as air) that surrounds the Earth. It is kept in place by gravity. Imagine the atmosphere as a large bubble of different gases that surrounds the planet.
The Earth's atmosphere helps protect all living things from harmful radiation from the sun and space. It keeps the Earth warm by trapping a certain amount of heat. If there was no atmosphere, most of the sun's heat would be reflected back into space and much of the Earth would be frozen.
A greenhouse gas is a gas in the atmosphere that absorbs heat energy from the sun.
The greenhouse effect refers to the way greenhouse gases trap and hold heat, warming the earth and the lower layer of the atmosphere.
The diagram below shows how the greenhouse gas effect works to warm the Earth.
Some greenhouse gases, including carbon dioxide (CO2), methane, water vapour and nitrous oxide are found naturally in the environment. But when the Industrial Revolution began in the late 1700s, humans began to emit far greater amounts of greenhouse gases from activities like burning coal and oil for transport and industry, cutting down forests and an increase in land used for agriculture.
These human activities are responsible for producing greater quantities of greenhouse gases than occur naturally. These extra gas molecules cause more of the sun’s radiation and heat to be pushed back down to Earth, rather than escaping into space. This is the underlying cause of our warming global climate.
CO2 is the main greenhouse gas linked to human activities and therefore driving climate change worldwide.
In the past, CO2 levels have naturally gone down with ice ages and up during interglacial (between ice ages) periods. Scientists know this from studying air bubbles trapped in ice in places like Greenland and Antarctica.
During ice ages, CO2 levels were at around 200 parts per million (ppm). During interglacial periods, they were around 280ppm. In 1950, following the beginning of the Industrial Revolution, the concentration went above 300 ppm.
Concentrations of CO2 have continued to increase as human populations and greenhouse gas emitting activities increase. Today, the global average of CO2 is around 414 parts per million – the highest in at least three million years.
The graph below shows the dramatic increase in CO2 following the industrial revolution in the late 1700s.
Graph from the US National Oceanic and Atmospheric Administration
One of the most obvious effects of climate change is increasing temperatures. The world’s average temperature has already increased by about 1.1 degrees Celsius compared with the average temperature 100 years ago. Warmer temperatures mean we will experience more frequent droughts and heatwaves. Storms are also likely to be more extreme and happen more often because a warmer climate can hold more moisture and energy.
A dramatic effect of warming global temperatures is the rapid melting of Arctic (the North Pole) and Antarctic (the South Pole) ice sheets. We are also seeing rapid melting of glaciers and ice on mountains around the world.
Another impact we often hear about is sea-level rise. Sea-level rise is related to the melting of ice sheets into the world’s oceans and the way water expands when it gets warmer. These processes are causing sea levels to rise at an average of about 3mm a year. Sea-level rise is a concern for low-lying coastal communities who may be vulnerable to coastal flooding, particularly when large storms hit.
Scientists have a good understanding of the way New Zealand is likely to be affected by climate change.
New Zealand will become warmer everywhere. Hot days – days above 25 degrees Celsius – are likely to be far more frequent and much of New Zealand may be frost free by 2100.
Areas of New Zealand that already receive lots of rain – such as the West Coast of the South Island – may receive even more rainfall in the future. Some areas may receive up to 40% more rainfall in winter.
Areas of New Zealand that don’t receive much rainfall – the far east and north of the North Island, e.g. Northland, Hawkes Bay, Gisborne and the Wairarapa – are likely to become even drier.
Drought can occur during extended periods of low rainfall. With fewer days with rainfall, longer dry spells and warmer temperatures, New Zealand will be much more prone to drought.
A warmer atmosphere can hold more energy and moisture. This will lead to more frequent extreme weather events for the world and New Zealand.
As drought-like conditions become more common in New Zealand, the likelihood of bush fires may increase.
The video below looks at a few things we’ve learnt in this lesson and explores the impacts of climate change in New Zealand.
What will a weather forecast look like in the future? To help paint a picture of the way New Zealand’s climate will change, NIWA has created this hypothetical weather forecast for the year 2050. The forecast explores the effects of climate change like flooding, bush fire and drought and the way these events may impact our day-to-day lives in the future.
(The quiz works best on kahoot, but if you prefer a text version, you can download it as a PDF here).
For more information about the science of climate change, visit our web pages aimed at school students. The things we can do to combat climate change, individually, and alongside our whānau, school and community, can and will make a difference.