Mr Brownlee’s letter (“Who to believe?”, Opinion, May 31) is right to draw attention to the uncertainties in the climate change issue, but he is wrong to imply that carbon dioxide is not important.

Atmospheric carbon dioxide is now nudging 400 parts per million. Only three years ago that figure was 390, so it is rising fast, almost certainly due to human activity.

Most climatologists now agree that this contributes towards warming, but disagree about how fast this will take place, or what the local consequences will be.

Climate change deniers often point out that there have been long periods when global temperatures stabilise or fall despite rising levels of carbon dioxide.

This ‘disproves’ man-made global warming, or so they say. However, this is a misunderstanding because there are many players in the climate change equation.

Sunspot cycles and volcanic activity together with some kinds of pollution can alter temperatures in the short and medium term.

Mr Brownlee worries that subsidised renewables (what about nuclear energy?) will ‘trash’ the economy. Surely not. The biggest threat comes from escalating spending on healthcare, benefits and compliances.

Roger H Brown

Weston-super-Mare