Climate change is occurring because of human activities that release excessive amounts of greenhouse gases into the atmosphere.
These greenhouse gases – such as carbon dioxide, methane and nitrous oxide – warm the air by trapping heat that radiates from the Earth’s surface. Over the last 200 years, concentrations of these gases in the Earth’s atmosphere have increased.
Temperatures are increasing
As concentrations of greenhouse gases have increased, the Earth has warmed. During the past century, the average global temperature has risen by 0.74ºC, with most of that occurring since 1970. At the poles, many areas are warming at a rate two or three times the global average.
The main causes of climate change
- Humanity’s increased use of fossil fuels – such as coal, oil and gas to generate electricity, run cars and other forms of transport, and power manufacturing and industry
- Deforestation - because living trees absorb and store carbon dioxide
- Increasingly intensive agriculture - which emits methane and nitrous oxide.
Today's industrialised countries - includng New Zealand - have built their economies on buring fossil fuels to provide electricity, transport and to develop industries. Developing countries are now beginning to do the same.
What makes climate change so urgent is that temperatures will continue to increase long after greenhouse gas emissions are curbed. Scientists believe the planet may reach a ‘tipping point’ at which time changes will become irreversible, such as the melting of ice sheets, which will drastically effect both sea levels and the planet's entire climate system.