As California’s landmark global-warming law requires the state to reduce greenhouse-gas emissions to 1990 levels by 2020, the state Air Resources Board has determined just what that goal will be: 427 million metric tons of greenhouse gases. The number was devised from some 13,000 separate calculations, from the impact of the aviation industry to the number of cows and horses in the state to where Californians source their power. California currently emits some 500 million metric tons of greenhouse gases per year; officials estimate that if no steps are taken, that will jump to 600 million metric tons in 2020. To that end, California also became the first state to require that large industrial plants track and eventually report their greenhouse-gas emissions. Meanwhile, the Los Angeles Harbor Commission approved a proposal to expand the city’s port — admitting that the project will increase emissions in the short term.

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