A changing climate

Where’s the evidence?

How do scientists know that greenhouse gases, such as CO2 are increasing?

an ice core


scientist with an ice core

Evidence that carbon emissions have increased over the years are measured through air trapped in ancient ice cores in Antarctica and Greenland. These show a gradual rise from 1800 – the beginning of the Industrial Revolution and the burning of fossil fuels in power stations, factories and cars. Since the 1950s, direct measurements have been made of carbon in the atmosphere from the observatory at Manua Loa in Hawaii.

These measurements show that the concentration of carbon dioxide in the atmosphere – measured in parts per million (ppm) has remained around 280 ppm for 650,000 years but in the last few years has increased to more than 385 ppm.

Most scientists agree that this increase is due to the burning of fossil fuels. The main reasons for an increase in carbon emissions are a growth in population and the increase in the amount of energy people use as we own more goods, enjoy more services and travel more.

The use of energy per person varies greatly across the world.

Compare the map of energy use per capita with the table of the world’s biggest emitters of CO2.

link to text version of map of energy use


Million tonnes of CO2 in 2002

United States












Brazil 851
Canada 680
United Kingdom 654

Source: World Resources Institute

climate fact

Together, the 25 countries with the largest emissions account for around 83% of world emissions.

Next: Why is this so important?