Why I deny

J o h n M i l n e a n d C a r o l y n Taylor (Letters, 25 April), Greta Thunberg and many others, c o nv i n c e d b y e v i d e n c e f o r man-made climate change, should note two inconvenient facts denying their conviction.

T h e s e i n c l u d e , f i r s t , t h e unprovability of greenhouse g a s e s a s t h e ma i n c l i ma t e c h a n g e move r s . T h e r e a r e more than seven additional influences, such as volcanism, sunsp ots, cosmic rays, Heinrich events and Milanko v i c h c y c l e s , a l o n g w i t h methane and CO2.

These are known variables, but there are, surely, unknown unknowns also. Such doubts m u s t u n d e r l i e u n r e a l i s e d predictions of climatic events from the computer programs they depend on.

Secondly, there is no proof at all that decarb onisation, hugely exp ensive, modifies climate changes.

We “deniers”, without base motivation, regard decarbonisation as wasteful and the prime imp or tance of manmade climate change as not proven.