("I got it wrong, Dr Karl admits", November 9)

Dear Editor,

What a con-test, hero Dr Karl Kruszelnicki up against Dr Nikki Williams (was the term "spin doctor" invented with Nikki in mind?). Dr Karl is off to a dud start, with a factor of 10 error – a mistake anybody who works with physical quantities will sympathise with. But if Dr Nikki is wrong, her error is an absolute of one – one inhabitable planet.

To get to the truth, take a sheet of graph paper (in your head). Plot cumulative emissions on one line under the "clean" coal scenario - 20 more years of increasing "dirty" coal usage, followed, perhaps, by a barely perceptible inflection point as some new plants in 2027 (say) deploy carbon sequestration.

Then plot a second curve assuming we aggressively replace coal with renewables from the present time. The technology develops exponentially. The carbon cost of deployment in 20 years time is reduced by the percentage of the energy market that is already renewable. Success breeds success, rather than a slightly delayed day of doom. It's not a myth, coal is the enemy of the human race. Branding it "clean" invites the public to relax, and that's the most dangerous effect of all.

Regards,
Carl Sparre
Eastwood