Answer:
All of them.
The continents all have some type of desert. Due to increased desertification, every continent can now be said to have a desert. Antarctica is also classified as a desert because it receives less than 500mm of precipitation per year, and deserts can be cold areas as well as hot.
Europe used to be the only continent without a desert. This is no longer the case. The process of desertification, resulting from degradation of dry farmland, has reached many countries in eastern Europe, particularly within the Russian federation countries. Russia, which is the largest country on the continent of Europe, has over 100 million hectares either affected by desertification or under threat of desertification, that is, the gradual encroachment of desert lands.