ANTHONY Weeden (Letters, December 30) emphasises the weakness of the alarmists who blame human emissions of atmospheric carbon dioxide for what they claim to be a progressive rise in the Earth’s surface temperature. In fact, the natural variation in solar radiation is by far the most important factor in global warming.

Isotopic and chemical analyses of cores drilled through the Antarctic’s Vostok Ice Sheet reveal the Earth’s surface temperature there during the past 400,000 years or so, showing regular 99,000 year cyclical changes followed by matching changes in atmospheric carbon dioxide content.

These indicate the Earth’s passage through the four most recent Ice Ages and subsequent Interglacial Warm Periods. Unless something cataclysmic happens, we are due to plunge into the next roller-coaster decline into the next Ice Age which no amount of man-made carbon dioxide can halt. But none of the ‘warmists’ wants to talk about this natural event!

Meanwhile, we can take comfort that our world has a good covering of water to provide us with a greenhouse blanket while we work out how to survive the next glacial onslaught!

Roderick Taylor, Abbotsbrook, Bourne End