YOU don’t require a degree in science to know that a sufficient increase in temperature causes ice to melt.

So, if no change in the planet’s temperature is occurring, could Peter Mullen (Echo, October 20) please explain why the polar ice caps and glaciers are melting?

Human activity may cause increases in CO2 levels, but it can’t cause the earthquakes and volcanic activity which have occurred over recent years.

The planet undergoes periodic cycles of change, including ice ages and changes in the magnetic poles, both of which are overdue.

Changes within the earth’s magnetic poles would cause earthquakes and volcanic activity, while directly affecting changes in climate.

Due to the location of the planet’s magnetic poles and the path of the planet’s magnetic field, any climate change would be more evident at the polar icecaps.

Therefore climate change may be due more to changes occurring beneath the Earth’s crust than human activity.

C T Riley, Spennymoor.