MIT Technology News: Cutting our overall use of fossil fuels has proved a daunting challenge, but it might be possible to get some relief from the effects of climate change by selectively reducing the particulate pollution we produce. Recent research suggests that if we can clean up diesel engines and primitive cookstoves in India and China, for example, that could delay the effects of greenhouse-gas buildup even if pollution from coal-fired power plants persists. A study released last week concludes that if every country...