The correct answer is - It appears as if the average global surface temperature increased by 0.6 degrees.
The trend of global warming has been becoming more intense, and thus more obvious in the past few decades. In big portion it is a result of the human activity because it contributes to increased amounts of carbon dioxide in the atmosphere which is the main gas that forms the Greenhouse effect, as well the destruction of the ozone layer which contributes to increased influence by the sun on the Earth's surface. The temperature of the surface has risen 0.6 degrees (at places 0.9), while the average air temperature has gone over 1 degree all over the world.