A thick haze of smog has descended on parts of northern China, pushing pollution to more than 20 times what the World Health Organization considers a safe limit.
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In Hebei, a province bordering Beijing to the north, concentrations of pollutant particles called PM2.5 reached upwards of 500 micrograms per cubic meter, according to Beijing's air quality index. The WHO's recommendation for maximum healthy exposure is 25 micrograms.
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According to the U.S. State Department's air quality guide, levels of PM2.5 between 301 and 500 micrograms are considered hazardous to health and constitute a "serious risk of respiratory effects in the general population," while anything above 500 is literally off the charts.

Most U.S. cities have a PM2.5 concentration of 20 or below.

Beijing aims to reduce air contaminants by 40 percent before the meeting using the same drastic pollution control measures employed before the 2008 Summer Olympics, according to Chinese media reports.

69 factories in the capital will be shut temporarily when Asia-Pacific leaders convene in Beijing, while 72 more will cut output. Surrounding cities like Tianjin and the heavily industrialized provinces of Hebei, Shanxi and Shandong will also adhere to strict anti-pollution policies, China Daily reported.

To minimize pollution from traffic congestion, government employees in Beijing will be given six days off, while public schools will be closed. A rule allowing drivers to use their vehicles only on alternate days will also be rolled out from November 3 to 12, reducing the number of cars on the road by 35 percent, the Beijing Traffic Management Bureau announced last week.

According to the plan, the United States will reduce carbon emissions 26-28 percent below 2005 levels by 2025, nearly twice the existing target—without imposing new restrictions on power plants or vehicles.

Tuesday's announcement is equally remarkable for China's commitment. For the first time, China has set a date at which it expects its emissions will "peak," or finally begin to taper downwards: around 2030. China is currently the world's biggest emitter of carbon pollution, largely because of its coal-dependent economy, and reining in emissions while continuing to grow has been the paramount challenge for China's leaders.
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The plan does not entail using the US Environmental Protection Agency's authority to regulate greenhouse gases, as the bulk of Obama's existing climate strategy does. Instead, it involves a series of initiatives to be undertaken in partnership between the two countries, including:

• Expanding funding for clean energy technology research at the US-China Clean Energy Research Center, a think tank Obama created in 2009 with Xi's predecessor Hu Jintao.


• Launching a large-scale pilot project in China to study carbon capture and sequestration.


• A push to further limit the use of hydroflourocarbons, a potent greenhouse gas found in refrigerants.


• A federal framework for cities in both countries to share experiences and best practices for low-carbon economic growth and adaptation to the impacts of climate change at the municipal level.


• A call to boost trade in "green" goods, including energy efficiency technology and resilient infrastructure, kicked off by a tour of China next spring by Commerce Secretary Penny Pritzker and Energy Secretary Ernest Moniz.