Without the greenhouse effect the mean temperature on Earth would be -18°C and there would be very little or no life. So the greenhouse effect itself is a good thing. The greenhouse effect traps some of the energy from the Sun, which keeps our planet at a suitable temperature for life.
Carbon dioxide, water vapour and methane are amongst the most common greenhouse gases. Since the start of the industrial revolution in about 1750 the levels of carbon dioxide have increased by 40 per cent.
Global warming is the increase in the mean temperature of the Earth. The ten hottest years since records began have been in the last 30 years. The mean increase in the last 100 years has been less than 1°C. This might seem small, but is enough to have devastating consequences on many species in different parts of the world.
As the percentage of carbon dioxide in our atmosphere has increased so has the Earth's mean temperature. Note that the shape of the first graph showing the amount of carbon dioxide in the atmosphere is 'exponential' and is a similar shape to graphs showing human population change over the same time period. When comparing graphs such as changes to carbon dioxide levels and temperature against time, note that the axes are drawn to different scales, and do not start at '0'.
The consequences of global warming are: