Regarding Matthew Laverack’s recent letter about Climate Change (The Press, July 26): while I respect his views on things architectural, he is out of his depth scientifically.

David Bellamy was well regarded as a populariser of science but came unstuck when he asserted the climate change crisis was ‘poppycock’. He based some of his argument on the notion that glaciers were advancing not retreating - data which was later entirely discredited.

Just over a hundred years ago the Swedish chemist Svante Arrhenius (Nobel Prize 1903) calculated that human CO2 emissions were sufficient to cause global warming - a finding backed up by data which shows that the average global temperature is increasing.

The evidence gathered over recent years, for example the retreat of glaciers, the reduction in the amount of polar ice and more extreme weather conditions (witness the recent extreme temperatures on the west coast of Canada) would indicate that globally we are experiencing relatively sudden and potentially very damaging climate change, probably caused by human activity.

I am at a loss as to why Mr Laverack should think this evidence is alarmist, that it is a sinister way of increasing taxation or that it is some kind of media narrative pushed down our throats.

Steve Bell, St. Pauls Terrace, York

Global warming is both man-made - and natural

The correspondence about climate change seems to be based on either/or thinking - the idea that either it is man-made, or it is natural. I suggest that it is both.

If humans did not exist, Earth’s climate might still be warming, just now. But it also seems that greenhouse gases produced by human activity are accelerating that warming. It is not enough to say that global warming is a natural trend - though that is true enough: the planet has gone through many such warmings before modern times. But humankind has to face up to its role in this warming, and attempt to do something about it.

David Martin, Rosedale Avenue, Acomb