Solar Influences on Climate (original) (raw)
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The sun affects our climate in direct and indirect ways. The sun changes in its activity on timescales that vary from 11, 22, 80, and 180 years and more. A more active sun is brighter due to the dominance of faculae over cooler sunspots; in this way, the irradiance emitted by the sun and received by the Earth is higher during active solar periods than during quiet solar periods. The amount of change of the total solar irradiance (TSI) during the course of an 11-year cycle, based on satellite measurements since 1978, is about 0.1%. This was first discovered by from the results of the SMM/ACRIM1 experiment, and was later confirmed by Fröhlich and Lean (1998). This finding has caused many to conclude that the solar effect on climate is negligible; however, many questions still remain about the actual mechanisms involved and the sun's variance on century and longer timescales.
Climatic Change, 1994
Recent precise observations of solar global parameters are used to calibrate an upgraded solar model which takes into account magnetic fields in the solar interior. Historical data about sunspot numbers (from 1500 to the present) and solar radius changes (between 1715 and 1979) are used to compute solar variability on years to centuries timescales. The results show that although the 11 year variability of the total irradiance is of the order of 0.1%, additional, longer lived changes of the order of 0.1% may have occurred in the past centuries. These could, for example, account for the occurrence of climate excursions such as little ice ages.
A discussion of recent evidence for solar irradiance variability and climate
Advances in Space Research, 2002
One of the over-arching questions, among others, to be addressed by studying Sun-Earth connections is: "Is the climate changing in a way we can understand and predict ?" The Earth's climate is the result of a complex and incompletely understood system of external inputs and interacting parts. Climate change can occur over a range of time scales, may be driven by natural variability, including solar variability, and/or anthropogenic causes and may be identified through the study of a variety of measurable parameters. Global climate change in response to human influences is one of the pressing threats facing science today. However, many of the external factors that govern our climate, including solar variability, cannot be adequately determined from existing operational observations. Since the Sun is the fundamental source of energy that sustains life on Earth, establishing its radiation environment, controls its temperature and atmospheric composition, the accurate knowledge of the solar radiation received by the Earth and understanding of its variability are critical for environmental science and climate studies. In this paper we point out the necessity of a new strategy, i.e., to study global solar properties, such as solar irradiance, solar shape, shape oscillations, and radius, to better understand the origin of solar-induced climate changes.
New findings increasing solar trend that can change Earth climate
Proceedings of the International Astronomical Union, 2009
Early attempts to find how solar activity can influence the Earth's climate involved comparison of many physical processes, such as dynamo mechanism, magnetic reconnection and eruptive activity, irradiance, open flux and particles variations, global atmospheric chemistry and dynamics.. . . However, such direct links seem to be weak even if the solar effects has been found to be stronger during extended maxima or minima of solar activity. Thus, temporal scales ranging from days to thousand of years must be investigated. A description of the most recent results on solar variability and its possible influence on the Earth's climate and atmosphere will be here addressed, with a particular emphasize on modulations of about 120 years (and harmonics). The extrapolation indicates a significant negative decrease of the solar signal, and consequently a decrease of the global Earth's temperature in the forthcoming years. Such a modulation is also testifying by other means, such as ...
Potential Role of Solar Variability as an Agent for Climate Change
1999
Numerical experiments have been carried out with a two-dimensional sector averaged global climate model in order to assess the potential impact of solar variability on the Earth's surface temperature from 1700 to 1992. This was done by investigating the model response to the variations in solar radiation caused by the changes in the Earth's orbital elements, as well as by the changes intrinsic to the Sun. In the absence of a full physical theory able to explain the origin of the observed total solar irradiance variations, three different total solar irradiance reconstructions have been used. A total solar irradiance change due to the photospheric effects incorporated in the Willson and Hudson (1988) parameterization, and the newly reconstructed solar total irradiance variations from the solar models of Hoyt and Schatten (1993) and Lean et al. (1995). Our results indicate that while the influence of the orbital forcing on the annual and global mean surface temperature is negligible at the century time scale, the monthly mean response to this forcing can be quite different from one month to another. The modelled global warming due to the three investigated total solar irradiance reconstructions is insufficient to reproduce the observed 20th century warming. Nevertheless, our simulated surface temperature response to the changes in the Sun's radiant energy output suggests that the Gleissberg cycle (≈88 years) solar forcing should not be neglected in explaining the century-scale climate variations. Finally, spectral analysis seems to point out that the 10-to 12-year oscillations found in the recorded Northern Hemisphere temperature variations from 1700 to 1992 could be unrelated to the solar forcing. Such a result could indicate that the eleven-year period which is frequently found in climate data might be related to oscillations in the atmosphere or oceans, internal to the climate system.
Influence of Solar Activity Cycles on Earth's Climate
Space Weather, 2007
Abstract: In order to determine the influence of mankind on climate change it is important to understand the natural causes of climate variability. A natural effect that has been hard to understand physically is an apparent link between climate and solar activity. From historical and geological ...
The role of solar forcing upon climate change
Quaternary Science Reviews, 1999
Evidence for millennial-scale climate changes during the last 60,000 years has been found in Greenland ice cores and North Atlantic ocean cores. Until now, the cause of these climate changes remained a matter of debate. We argue that variations in solar activity may have played a significant role in forcing these climate changes. We review the coincidence of variations in cosmogenic isotopes (C and Be) with climate changes during the Holocene and the upper part of the last Glacial, and present two possible mechanisms (involving the role of solar UV variations and solar wind/cosmic rays) that may explain how small variations in solar activity are amplified to cause significant climate changes. Accepting the idea of solar forcing of Holocene and Glacial climatic shifts has major implications for our view of present and future climate. It implies that the climate system is far more sensitive to small variations in solar activity than generally believed.
Solar Variability, Galactic Cosmic Rays and Climate: A Review
Earth Science India, 2014
Climate is among the most important natural resources for all living beings. The main external and internal driver for climate change is variability of the Sun. The Sun is the ultimate source of the energy on the Earth and play a key role in its climate change. What is still not known and needs to be found is the extent to which these variations in solar behavior affect the total energy that the Sun emits. The small variation in the solar irradiance and changes in its spectral distribution leads to a large variation in climate. An attempt has been made to report the present understanding of the solar variability and its consequences on the variability of solar irradiance which exhibits 11-year cyclic variation and modulation on higher time scale. Galactic Cosmic Rays (GCR) reaching the Earth's atmosphere is modulated by the solar wind and geomagnetic field, which also exhibit 11-year cyclic variation. In the present paper, we have reviewed our current understanding on physics of solar variability, galactic cosmic rays and their effects on the Earth's climate.