Study: Global Warming Means Smoggier Autumns in US Southeast - "The argument is that climate change affects the trees, the trees release a chemical that may help them cope with harsh conditions, and the chemical produced by the trees leads to an increase in ozone," Field said in an email.

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Study: Global Warming Means Smoggier Autumns in US Southeast - "The argument is that climate change affects the trees, the trees release a chemical that may help them cope with harsh conditions, and the chemical produced by the trees leads to an increase in ozone," Field said in an email.