Intensive [non-organic] farming 'massively slowed' global warming - environment - 14 June 2010 - New Scientist

The emissions were avoided because the green revolution boosted crop yields – for instance by promoting hybrid varieties that had higher yields, and through widespread distribution of pesticides and fertilisers. This meant that more food could be produced without having to slash vast swathes of forest to expand farmland.

Flashback: 'Organic farming may counter climate change,' report says - Climate Change, Environment - The Independent

Organic farming can play an important role in countering climate change, a new report suggests today.
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The report suggests that widespread adoption of organic farming practices would offset 23 per cent of the UK's greenhouse gas emissions from agriculture through soil carbon sequestration alone, more than doubling the Government's target of a 6-11 per cent reduction by 2020.