The weather naturally changes from month to month, and from year to year. The climate can be described as the weather’s long-term characteristics, such as average values and variations. Thirty-year periods are usually used to study climate development.
By looking at series of measurements over a long time, we can see that the global average temperature has risen. It has risen at a faster pace that during any other historical period, due to mankind’s greenhouse gas emissions. The rate of warming is almost one degree compared with pre-industrial times. Observed changes to glaciers or Arctic sea ice, for example, support the picture of ongoing warming.
Greatest change in the north
The temperature development differs in different places. The biggest change is taking place at northerly latitudes, in the Arctic, where the warming is the greatest. Following factors contribute: snow and ice are melting, and the ground is becoming darker and absorbing more heat. Another important factor is that the surface of the sea is becoming exposed. The surface of the sea is darker than sea ice and gives off heat, which again contributes towards warming.
During the last 30 years, Sweden has become warmer during all four seasons. The biggest increase in temperature can be seen during the winter in northern Sweden, and the smallest increase during the autumn.
The Earth’s climate has thus already become warmer, and this change will continue. The amount of warming will depend on greenhouse gas emissions around the world, and how quickly these emissions can be reduced. Different types of development can be studied using climate scenarios.
In Sweden, the greatest increase in temperatures is expected to occur during the winter, with the biggest changes of all involving periods of extended cold becoming shorter and much milder. During the summer, periods with heatwaves will become more common and more intense.
International research on the climate and its development is compiled every year by the UN Intergovernmental Panel on Climate Change (IPCC). These summaries form an important basis for negotiations and for different types of decisions within society. The next summary will be complete in 2021.