I have recently baked my first muffins ever! Was a bit disappointed though after I had opened the stove door to check things out and they had gone flat immediately. Some easy explanation please?

I look after a pendulum clock at the University of Cambridge which I hope will achieve an accuracy of less than 1 second of error per year (www.trin.cam.ac.uk/clock). It has a temperature-compensated pendulum, but is sensitive to air pressure variation.

If the mean global temperature was to rise by, say, 4 °C, would there be any change to mean air pressure at sea level? Put simply, would global warming cause the clock to speed up or slow down?

Hugh Hunt, Keeper of the Clock, Trinity College, University of Cambridge, UK