Rising solar and thermal greenhouse radiation drive rapid warming over continents

Abstract

Rising anthropogenic greenhouse gases, such as CO2, CH4, N2O and others, are known to absorb and emit terrestrial thermal radiation back to the Earth's surface, leading to radiative forcing and rising surface temperatures. Nonetheless, radiation measurements now show that the rapid increase in temperature over continents since the end of the last century, which is more than twice as large as the average global warming, is also related to a clearing of the sky over land surfaces, which leads to an increase in sunshine hours, and hence, increasing solar radiation absorbed at the Earth's surface. By contrasting rising temperatures with annual sunshine hours and solar and thermal radiation in Central Europe, the measurements show that thermal radiation steadily increases owing to the rising greenhouse effect. However, the rapidly increasing warming since the end of the last century has been reinforced by a strong increase in solar radiation at the surface, resulting from rising annual sunshine hours as a positive greenhouse warming feedback, which is larger than the increase in thermal greenhouse radiation, and hence, the strongest driver of the rapidly increasing warming over continents. The rapid temperature increase in Central Europe, of more than one degree over the last decade, is larger in lowlands than in the Alps.

Keywords

• solar radiation
• thermal greenhouse radiation
• radiation measurements
• rapidly increasing warming over continents