The greenhouse effect is related to the phenomenon of an increase in average surface temperature known as

The greenhouse effect is related to the increase in the average surface temperature which is considered "global warming". Global warming is the result of an increase in gases like methane, carbon dioxide, and other factors that lead to a rise in the planet's temperature. 

Europeans are more concentrated in urban areas.

The us is first  the  u.s. economy  remains the  largest in the world  in terms of nominal  gdp. however, the  u.s. economy  loses its spot as the number one  economy  to china when  measured  in terms of  gdp  based on ppp. in these terms, china's  gdp  is $23.19 trillion exceeds the  u.s. gdp  of $19.42 trillion