Radiation and Climate Change during the Instrumental Observation Period

Abstract

 For investigating climate changes, the use of meteorologically observed data was delayed. The reason for this delay was partly due to the belief that observational records were of too short duration, and the ranges of the change too small to detect climate changes. During the last half a century, meteorological records started to be used, especially for temperature and precipitation. The use of radiation was further delayed, owing to the belief that radiation is a stable component, lacking in temporal changes. Radiation, like other climatic elements, has measurable variations, whose ranges are sufficiently large to play a role in climate changes. The present article reviews the way in which shortwave (solar) global radiation was integrated into the research of climate changes. The developing process toward a realistic radiation balance of the atmosphere and the earth's surface was presented. The earlier faulty belief that the atmosphere absorbs only about 17% of the primary radiation from the space, giving unnaturally large solar radiation to the earth's surface has been systematically explained and the way to remedy this error is presented. Further, the solar global radiation was found to change in a decadal time scale as much as 8 Wm⁻². The first Global Brightening was experienced in early middle 20^th century, followed by the Global Dimming of the thirty years from 1960 to 1990, which was followed by a steep recovery to present. Aerosol was found as the main cause for the variation in solar radiation. These changes significantly affected other earth's surface processes, such as temperature and glacier mass balance. These discoveries were accomplished by the direct observation of radiation at the earth's surface.