Hi:
Your reader David Kempton presents his opinion that "Conservatively, that ratio is about 1,000 who believe climate change is mainly caused by human activity to every one who believes otherwise." I must assume opinion since there is no survey of scientists that puts it at anything approaching this ratio.
The most thorough study was by the Statistical Assessment Service at George Mason University. It's detailed survey of 489 key climate scientists working in the field found only 74% would agree with a similar statement. This is in close agreement with the numbers at the major climate change review group, the I.P.C.C., which lead that group to publish a 90% confidence level that the .74 degree increase in global temperature in the last 100 years was caused in part by people (i.e. 9:1)

Of course the real issue is not the small change that has happened but will this be the catastrophic danger, requiring major changes to society. In the same survey in answer to the question of does global warming represent a catastrophic risk only 41% agreed. Of course a good horror story is always going to get more press than boring old science, but it is important that science does get published on an even basis.
I also note Mr. Kempton seems worried that Dr. Bell is not a "climate scientist". I have to ask does this mean he is worried about David Suzuki getting so much press too? After all his major activity is as a reporter and his scientific training is all as a geneticist. As a final word to the media a final statistic from this survey. "Only 1% of climate scientists rate either broadcast or cable television news about climate change as very reliable.

