The climate in the 21st century

Abstract

Human activity has perturbed the Earth's energy balance by altering the properties of the atmosphere and the surface. Increasing greenhouse gas concentrations are expected to have significant impacts on the world's climate on a timescale of decades to centuries. Evidence from long-term monitoring studies is now accumulating and suggests that the climate of the past few decades is anomalous compared with past climate variation. Global mean surface temperatures have increased for more than 0.6°C since the late 19^th century. The 20^th century has been anomalously warm, with the 1990s the warmest decade and 1998 the warmest year this millennium. In Slovenia average air temperature has increased by 1± 0.6 °C in the last 50 years. Climate models predict that the mean annual global surface temperature will increase 1.5–6°C by 2100, with warming more pronounced at higher latitudes. Relatively greater increases are expected in winter than in summer. All climate models predict an increase in global mean precipitation, but some regions might get drier. Forecasts of climate change are inevitably uncertain, especially multi decadal forecasts and regional climate change predictions.