Update: as expected, Williamson has declined to take up my suggestion. But here is a chart summarising over a thousand experimental results of acidification, taken from here. Note that the effect is more positive than negative in the region of expected pH change (up to 0.3)

I have sent the following letter to Dr Phil Williamson at the University of East Anglia:

Dear Dr Williamson,

In your recent piece about my Times article, you wrote:

`Those wishing to draw attention to ocean acidification as an environmental threat should not overstate the case. It is possible that ocean acidification impacts may be less widespread than indicated by "pessimistic predictions".

Would you agree that the following quotes from an article by Charlie Veron on the Yale 360 website ( http://e360.yale.edu/feature/is_the_end_in_sight_for_the_worlds_coral_reefs_/2347/), which were relayed by the New York Times, represent an egregious example of `overstating the case' and a highly unbalanced analysis. Will you be criticizing this? If not, I would be interested to know why not.

`The potential consequences of such acidification are nothing less than catastrophic.'

Nothing less?

`No doubt different species of coral, coralline algae, plankton, and mollusks will show different tolerances, and their capacity to calcify will decline at different rates. But as acidification progresses, they will all suffer from some form of coralline osteoporosis.'

All? Many studies show increased calcification rates at realistic falls in pH.

`The result will be that corals will no longer be able to build reefs or maintain them against the forces of erosion. What were once thriving coral gardens that supported the greatest biodiversity of the marine realm will become red-black bacterial slime, and they will stay that way.'

Will become?

The article is entirely free of real results of any kind. It completely ignores recent meta-analyses and many recent studies, as I am sure you will agree.

Or are you only required to respond to those who argue that the threat is exaggerated, not to those who do the exaggerating?

All the best

Matt Ridley