Dear Bobble,
It is true that the Earth has always gone through natural periods of warming and cooling, mostly due to changes in the sun's activity or changes in the geometric relationships of the Earth's orbit and tilt. Unfortunately, this is not the cause of the current warming.
The sun is actually quieter than it has been for a hundred years, but the earth continues to warm at a rate never before experienced. there is now absolutely no doubt in the minds of virtually all climate scientists that warming is primarily the result of a 30 percent plus rise in carbon dioxide levels in the atmosphere due to human activities over the last 300 years or so.
If greenhouse gas emissions, such as carbon dioxide, are not brought under control within six years, then it will almost certainly be too late to avoid an awful future of extreme weather and dramatically rising sea levels, bringing economic and social chaos across the globe.
Bill McGuire
Footrpint Friends Science Advisor and
Professor of Geophysical & Climate Hazards at University College London