A Fonterra Guide to Climate Change

A: CLIMATE CHANGE AND NEW ZEALANDWhat is climate change?Climate change, or global warming, refers to increases in the average temperature of the Earth’s oceans and the airnear the surface. This warming of the planet is considered by many climate scientists to be caused by increasing levelsof greenhouse gases in the atmosphere as a result of human activities. The greenhouse gases trap heat from the sun,acting rather like a glasshouse. Climate scientists expect the Earth’s average temperature will increase by between 1.4and 5.8°C this century. The main greenhouse gases are:• carbon dioxide (CO2) – produced when fossil fuels like coal and oil are used to generate energy. It is absorbed bytrees, so forests act as a carbon dioxide ‘sink’;• methane (CH4) – produced naturally, as well as from landfill sites, rice fields, wastewater treatment, natural gasand petroleum systems, and by livestock;• nitrous oxide (N20) – produced by natural processes as well as from agriculture, changes in land use and fossil fuelcombustion.Carbon dioxide is by far the largest source of greenhouse gas emissions, accounting for nearly three quarters of totalemissions worldwide.Extra heat is kept in the air by‘greenhouse gases’ producedfrom human activity.Some sunlight is bouncedback into space.Some heat is releasedinto space.Less heat is able to bereleased into space.Some heat is naturallykept in by gases in the airlike water vapour.Source: Ministry for the EnvironmentClimate change, or global warming, refers toincreases in the average temperature of theEarth’s oceans and the air near the surface.2