IT might surprise readers to know that there has been no global warming for 17 years.

I read with interest the recent report (Echo, 24 Feb) that volcanoes are responsible for this, because their emissions into the atmosphere shut out some of the sun’s energy.

There have been other explanations for this temperature flat-line recently, and I submit that this puzzle shows that the science is not settled at all.

During this recent temperature hiatus the sun has been, and still is, going through a very quiet spell, its lowest for about 100 years.

Yet scientists are reluctant to link the two facts together.

All this suggests to me that the global warming of the second half of the last century was caused by human carbon dioxide and the sun, maybe, in roughly equal parts.

If, on the other hand, the sun is playing only a very minor part and it is humans who are largely responsible, then there must a negative effect going on at the moment to counteract the increased temperature that should be caused by the present increases in carbon dioxide.

The weird thing is that whatever this negative effect is (volcanoes or otherwise), it is exactly cancelling out the positive human global warming.

Why should this be?

In spite of all this, it has to be a good idea to cut down on carbon emissions since a lot of it comes from industry, and curbing this would at least make our planet cleaner.

Dr John McCue, Norton, Stockton.