Many scientists believe that human activity has caused an increase in the greenhouse effect, causing global warming and climate change.

Since about 1850, there has been a steady increase in the burning of fossil fuels for industry, in the carbon dioxide levels in the atmosphere and in the average temperature of the Earth.

However, CORRELATION DOES NOT MEAN CAUSATION i.e. this does not necessarily show that burning fossil fuels is the cause of global warming.

Arguments against carbon dioxide causing the rise in temperature:

The Earth's temperature goes through cycles of hot and cold
Some say that the initial methods of measuring atmospheric carbon dioxide were inaccurate and that the trends that some arguments depend on may not be fully reliable. We also do not have records of carbon dioxide levels around the world for a very long period, as initial measurements were limited to certain locations

Arguments for carbon dioxide causing the rise in temperature:

There greenhouse effect provides a clear mechanism by which global warming could be caused by the burning of fossil fuels. The principles behind the greenhouse effect have been proven in the laboratory.
The temperature of the Earth's surface and the level of carbon dioxide in the atmosphere have both risen in recent years
Many say that the rise in temperature is greater than would have been expected by the normal temperature cycle.
Some scientists say that the recent activity of the sun should be linked with a fall in temperature, not a rise (And that this is evidence for a man-made cause)