Sir, – A DIY Global Warming Experiment. Your readers are invited to a ground-breaking experiment at the 8th Annual Christmas Lecture in Welbury Village Hall from 4 to 5 pm on Sunday, January 18. It’s free, but please ring me on 01609 882501 to reserve places.

With politically sensitive scientific issues, it can be hard to know who to believe. History cautions us against blindly following authority. So it's good to test things for yourself, while being aware of the limitations.

The orthodox position says global warming in the last century was too fast for natural processes and is mainly caused by excess atmospheric carbon-dioxide (CO2) produced since the industrial revolution. Some other scientists say we don't know enough about natural processes, or about water and clouds, and the amount of CO2 in the atmosphere is too small to cause the warming.

If you google "global warming in a jar" you may find some home experiments, claiming to show it's warmer with CO2 in the jar, but they have (as far as I've found) not yet measured the results to compare them with the real atmosphere. We hope to do better. And yes, you can “try this at home”, and I would be interested in your results.

MIKE O’CARROLL

Welbury, Northallerton.