This is a picture of Beijing on a particularly bad day. This isn't fog, it's smog, a combination of haze and smoke/pollutants.
Death rates due to air pollution are the highest in China, unsurprisingly. As of 2008, the death toll was at nearly half a million compared to the next highest India at around one hundred and sixty eight thousand, as reported by the World Health Organization.
The cause of these deaths stem from the burning of coal, gas, oil, and other natural gasses for electricity, transportation, and industrial factories. Electricity is the largest cause of pollution at a rather shocking 37% while transportation is close behind with 31% of all CO2 emissions. Industry falls a little farther behind at 15% while the other 16% is made up of everything else. To cut down CO2 emissions by over a third, we would simply need to phase out power plants that burn coal and fuel and substitute them with things such as Nuclear power plants or solar energy.
The city of Beijing has smog so dense that it can be observed from the International Space Station.
The Chinese government is also hypocritical in their claim of attempting to lower pollution levels. On one hand, they offer a reward to the city of Beijing for reducing CO2 emissions, but on the other they agree to fund fifteen new large-scale coal mining projects. Seeing as the burning of coal and other natural gasses are the root of the problem regarding pollution, the Chinese government isn't helping the environment, simply destroying it even faster. This is not just a problem in China, however. The entire world has to deal with the issue of air pollution, China being the most extreme of examples.
The reduction of CO2 emissions is paramount to the survival of the human species and the preservation of our world. If we continue on the path we are on today, the world will become uninhabitable, which would mean the end for our species and perhaps all life on Earth. The best case scenario if this does happen is humans survive at a distance, perhaps orbiting Earth in some sort satellite or the colonization and terraforming of Mars where we can begin anew the destruction of a planet.