We can directly measure the results that solar forcing had, such as in driving CO2 out of the oceans by heating them up, and the resultant increase in temperature that this increase caused.

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But the main external candidate is solar, and more work is required to improve the "paleo" solar forcing record and to understand how the climate system responds both globally and regionally to solar forcing.

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Perhaps most importantly, intense pressure from heavily subsidized Chinese manufacturers is driving a surprisingly competitive solar market, forcing Solyndra to get costs down faster than the start-up firm could achieve.

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For the precise method that we subsidise solar power in the UK is by forcing all users of electricity to pay more to the generators of solar power.

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When the federal government tried to speed up cuts in the feed-in tariff for solar power, several states put up a fight, forcing a partial retreat.

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When solar equipment manufactures began posting big losses during 2011, forcing some to close factories or even file for bankruptcies, many of them wondered: when will the market recover?

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China, which has used state owned banks and utilities to finance solar factory expansion and create domestic demand for solar panels, will continue to dominate solar manufacturing, though the government is reportedly working on rescuing only 12 large companies and forcing mergers in others.

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