During the second half of the 20 th century, the average temperature of the earth’s atmosphere increased by 0.5°C. That doesn’t seem much, but scientists think that this increase has already had consequences:
The recent frequency of record years: 1999, 2002, 2033 and 2004 were the four hottest years since the start of meteorological recordings in the 19 th century (study by James Hansen, of the Goddard Institute for Space Studies at NASA);
An increase in the number of natural disasters, all causes taken together:
- 10 to 20 per year from 1900 to 1960,
- 70 to 80 per year from 1960 to 1980,
- 160 to 220 per year from 1980 to 1990,
- 350 to 400 per year between 1990 and 2000, in other words, double that of the previous decade.
Among the causes of natural disasters, the number of earthquakes remained quite stable from 1980 to 2000, whereas the frequency of hurricanes and floods increased. Indeed, it is disasters linked to the climate that are becoming more numerous:
an increase of between 10 and 20cm in the sea level;
the displacement of tropical species towards the North, such as barracudas along the French coasts and tropical African fish in the Mediterranean. There have also been changes in the behaviour of migrating birds: migrations have been delayed, shortened in distance or even cancelled altogether.
Scientists think that global warming is very probably due to a massive discharge of greenhouse gases by human activities. These emissions result above all from our consumption of fossil energy. |