Global warming is a result of human activity. In 1985 there was a big conference in Austria where 89 climate researchers from different countries took part. After long discussions the scientists declared that the climate of the planet had changed. Indeed, it is warmer now than it was years ago. It can be clearly seen in the north. In the Arctic some places are ice-free now and polar bears have lost the place where they lived. The sea level has risen as well. The situation is getting more and more serious. Global warming is a great problem which needs to be solved in the near future.