IN your article (LET, July 12), it is stated that global temperatures are rising faster now than at any time in the last 1,000 years and the carbon dioxide levels are higher than at any time in the last 400,000 years.

If the present levels are due to human activity, why were they so high then, when there wasn't any? I have asked this question numerous times, but have never received an answer.

I am not disputing the facts -- the Earth is warming; carbon dioxide levels are rising. And there might be serious implications, but the fact that these effects coincide with human activity does not necessarily mean that one is the case of the other.

DAVID AINSWORTH, Earnsdale Road, Darwen.