Ilmastonmuutos pääkaupunkiseudulla

Greenhouse gas emissions caused by human activity have already warmed the climate of Earth by more than one degree. Significant changes have been observed e.g. in the intensity of heatwaves and heavy rainfall. Future climate change depends on human emissions, but it is likely that the global mean temperature still rises by another 1–2 degrees by the end of this century. The ongoing global warming is already visible in the climate of the capital region. Many of the observed changes are consistent with what human-caused intensification of the greenhouse effect will bring. During the past 60 years, the average temperatures have risen in all seasons, but the strongest warming has been observed in winter. Precipitation has increased in the winter season, but no statistically significant trends in precipitation can be observed in other seasons. In addition to the average climatic conditions, heatwaves have intensified with a stronger increase in the inland regions than on the coast. In this report, the latest climate change projections based on CMIP6 climate models and SSP greenhouse gas scenarios used in the IPCC's Sixth Assessment Report are presented. According to the moderate SSP2-4.5 emission scenario, the average temperatures are predicted to rise in the capital region by 2.5–3 degrees in all months from the period 1981–2010 by the period 2040–2069. The warming is slightly weaker than in Finland on average, and the changes are somewhat larger in winter than in summer. A milder winter climate results in a further decrease in snow and ice cover. The rising temperatures in summer bring stronger heatwaves, heavy rainfalls and prolonged periods of droughts. There are no clear signs of change in the windiness, and thus winter storms are not predicted to be notably stronger in the future than they are now. Instead, the amount of precipitation induced by winter cyclones increases and comes more often as rain than snow. The sea level is not projected to rise much by the mid-century, but by the end of the century it is estimated to rise by about 25 cm from its current level. Even according to the most optimistic emission scenario, the climate in the capital region would warm by more than one degree by the 2080s. The climate change by the end of the century experienced by future generations is highly dependent on human emissions, and one must be ready to prepare for some degree of change. On the other hand, the climate in the capital region is subject to significant natural variability, and therefore cold periods of weather may occur also in the future.