During the last century, due to the greenhouse effect, the average temperature of our planet increased by around one degree Celsius. This may seem to be another negligible increase, but the climate is a very delicate mechanism that depends on very many interconnecting variables: if any of them are altered, there may be unforeseeable consequences. Some consequences, on the contrary, are already clear. The Antarctic has lost over 2500 billion tons of ice, while at the other pole in the frozen Arctic Ocean, during the summer the ice is disappearing even where previously it never melted. The North-West Passage is the legendary and very dangerous route connecting the Atlantic and Pacific Oceans through the frozen Arctic Ocean. Other consequences of climate change are: increase in the frequency and intensity of extreme climatic events, increase in the risk of desertification  in some areas, rise in the sea level, loss of biodiversity, problems in food production.
