Variations in solar radiation have been a major driver of climate change for billions of years of geological time, but its role in recent warming has been found to be insignificant.
Video Solar activity and climate
Geological time
The Earth formed about 4.54 billion years ago with the increase of the solar nebula. Volcanic outgassing may create a primordial atmosphere, which barely contains oxygen and will be toxic to humans and most modern life. Most of the Earth is melting because it often collides with other bodies that cause extreme volcanism. Over time, the planet cools and forms a solid crust, eventually allowing liquid water to exist on the surface.
Three to four billion years ago the Sun only emitted 70% of its current strength. Under the current atmospheric composition, this past solar luminosity will not be enough to prevent water from uniform freezing. However, there is evidence that liquid water already exists in the Hadean and Archean times, leading to what is known as the vague Sun paradox. The hypothesis solution for this paradox includes a very different atmosphere, with a higher greenhouse gas concentration than currently available.
Over the next 4 billion years, the output of solar energy increases and the composition of the atmosphere changes. The Great Oxygenation event about 2.4 billion years ago was the most important change. Over the next five billion years, Sun's last death of that time became a red giant and then a white dwarf would have a dramatic effect on the climate, with the red giant phase likely to end life on Earth.
Maps Solar activity and climate
Measurement
Since 1978, solar radiation has been measured directly by satellites, with excellent accuracy. This measurement shows that the total solar radiation of the Sun fluctuates by -0.1% for ~ 11 years of solar cycle but has not increased since 1978.
The precipitation of the sun before 1970 is estimated using proxy variables, such as tree circles, number of sunspots, and cosmogenic isotope abundances such as 10 Be, all calibrated to direct post-1978. measurement.
Sun activity has experienced a downward trend since the 1960s, as shown by the 19-24 solar cycle, where the maximum number of sunspots is 201, 111, 165, 159, 121 and 82, respectively.
In the three decades after 1978, a combination of solar and volcanic activity is thought to have little cooling effect. A 2010 study found that the composition of solar radiation may have changed slightly, with increased ultraviolet radiation and other wavelength decreases. "
Modern era
In the modern era, the Sun has been operating within a band that is narrow enough so that the climate is less affected. The model shows that solar and volcanic activity can explain the relative warm and cold periods between A.D. 1000 and 1900.
Little Little Age
One of the long-term historical correlations between solar activity and climate change is the minimum of 1645-1715 Maunder, periods of little or no sunspot activity that partially overlap with the "Little Ice Age" where cold weather prevails in Europe. The Little Ice Age covers about the 16th century until the 19th century. Whether solar activity is low or other factors that cause cooling is debatable.
The Minimum SpÃÆ'¶rer is associated with significant cooling periods between 1460 and 1550.
A 2012 paper instead links Little Ice Age with volcanism, through an "unusual 50-year episode with four explosive rich rich sulfur," and claims "major changes in solar radiation are not needed" to explain the phenomenon.
A 2010 paper shows that a new 90 year period of low solar activity will reduce the global average temperature by about 0.3 Â ° C, which will be far from enough to offset the increased coercion of greenhouse gases.
The Holocene
Many paleoenvironmental reconstructions have identified the relationship between solar and climate variability. Arctic paleoclimates, in particular, have linked variations in total solar radiation and climate variability. A 2001 paper identifies the ~ 1500 year solar cycle which is a significant influence on the North Atlantic climate along the Holocene.
Fossil fuel era
The relationship between recent solar and climate activity has not been quantified and has not been identified as the main driver of warming that has occurred since the early 20th century. Man-made forcings are needed to reproduce the late-twentieth-century warming. Several studies have linked irradiation driven by increasing solar cycles with parts of 20th century warming.
The three mechanisms proposed by which solar activity affects climate:
- The solar radiation changes directly affect the climate ("radiation imposition"). This is generally regarded as a minor effect, because the measured amplitude of the variation is too small to have any significant effect, there is no multiple amplification process.
- Variations in ultraviolet components. The UV component varies more than the total, so if the UV for some reason (as yet unknown) has a disproportionate effect, this might explain a larger solar signal.
- Effects are mediated by changes in galaxy cosmic rays (which are affected by solar wind) such as changes in cloud cover.
Climate models can not reproduce the rapid warming observed in recent decades when they consider only variations in total solar radiation and volcanic activity. Hegerl et al. (2007) concludes that greenhouse gases force "very likely" to cause most of the global warming observed since the mid-20th century. In making this conclusion, they allow the possibility that climate models have underestimated the effects of solar power.
Another line of evidence comes from seeing how the temperature at different levels in Earth's atmosphere has changed. Models and observations show that greenhouse gases produce a tropospheric heating, but cool the stratosphere. The depletion of the ozone layer by chemical coolants stimulates the stratospheric cooling effect. If the Sun is responsible for observing warming, warming of the troposphere on the surface and warming up the top of the stratosphere would be expected as an increase in solar activity would fill ozone and nitrogen oxides.
Evidence line
Assessment of solar activity/climate relations involves much independent evidence.
Sunspots
Initial research sought to find a correlation between weather activity and sunspot, largely without significant success. Subsequent studies concentrate more on solar activity associated with global temperatures.
Irradiation
It is important to understand the possible solar impacts of terrestrial climate as an accurate measurement of solar power. Accurate measurements are only available during the satellite era, and even open to debate: different measurements find different values, because different cross-calibration measurement methods are performed by instruments with different spectral sensitivity. Scafetta and Willson found significant variations of solar luminosity between 1980 and 2000. But Lockwood and Frohlich found that solar power declined after 1987.
The Third Assessment Report on Intergovernmental Assessment Report (TAR) concludes that the measurable impact of recent solar variations is much smaller than the effects of greenhouse gas amplification, but recognizes that scientific understanding is bad with respect to solar variations.
Estimated changes in long-term solar radiation have decreased since TAR. However, the empirical results of detected tropospheric changes have strengthened evidence to force the sun on climate change. The mechanism is most likely to be considered as a combination of direct coercion by TSI changes and the indirect effects of ultraviolet (UV) radiation on the stratosphere. At least is an indirect effect caused by galaxy cosmic rays.
In 2002, Lean et al. states that while "There is... growing empirical evidence for Sun's role in climate change on multiple time scales including the 11-year cycle", "changes in the terrestrial proxies of solar activity (such as cosmogenic isotopes 14C and 10Be and geomagnetic indexes a) can occur in the absence of long-term (ie, secular) solar radiation... because the stochastic response increases with the amplitude of the cycle, not because there are actual secular irradiation changes. "They conclude that because of this," long-term climate change may emerge to track the amplitude of the solar activity cycle, "but that" the coercion of solar radiation of the climate is reduced by a factor of 5 when the background component is removed from the historical reconstruction of total solar radiation... This suggests that the general circulation model (GCM) exaggerating the role of solar radiation variability. "A 2006 review showed that sunlight is bright has a relatively small effect on the global climate, with little possibility of a significant shift in solar output over long periods of time. Lockwood and FrÃÆ'¶hlich, 2007, found "substantial evidence for the influence of the sun on the pre-industrial climate of Earth and Sun may have been a factor in post-industrial climate change in the first half of the last century", but that "Over the past 20 years, all the trends in the Sun that could have an impact on Earth's climate have been in the opposite direction required to explain the observed rise in global average temperature. "In a study considered to be geomagnetic activity as a measure of known sun-terrestrial interaction, Love et al. found statistically significant correlations between sunspots and geomagnetic activity, but not between global surface temperatures and the number of sunspots or geomagnetic activity.
Benestad and Schmidt concluded that "the most likely contribution from the sun to forcing global warming is 7 Ã, Â ± 1% for the 20th century and negligible for warming since 1980." This paper disagrees with Scafetta and the West, who claim that solar variability has a significant effect on climate coercion. Based on the correlation between certain climates and the reconstruction of forcing the sun, they argue that "realistic climate scenarios are those described by large pre-industrial secular variability (eg, , paleoclimate temperature reconstructions by Moberg et al.). With TSI experiencing variability secular low (as shown by Wang et al.). Under this scenario, they claim the Sun may have contributed 50% of global warming observed since 1900. Stott et al. estimated that residual effects of prolonged high solar activity over the past 30 years caused between 16% and 36% of warming from 1950 to 1999.
Live measurements and time series
Both direct measurements and the proportion of solar variation correlate well with Earth's global temperature, particularly in recent decades when both quantities are best known.
Day/Night
The global average daily temperature range has decreased. Daytime temperatures do not increase as fast as night temperatures. This is the opposite of expected warming if solar energy (falling primarily or completely during the daytime, depending on the energy regime) is the primary means of forcing. Nevertheless, the pattern is expected if greenhouse gases prevent the escape of radiation, which is more prevalent at night.
Hemisphere and latitude
The Northern Hemisphere heats up faster than the Southern Hemisphere. This is the opposite of the expected pattern if the Sun, which is currently closer to Earth during the austral summer, is a major climate coercion. Specifically, the Southern Hemisphere, with more marine territory and less land, has lower albedo ("white") and absorbs more light. The Northern Hemisphere, however, has a higher population, industry and emissions.
In addition, the Arctic region warms faster than Antarctica and is faster than northern latitudes and subtropics, although the polar regions receive less sunlight than low latitudes.
Altitude
Solar power must warm the Earth's atmosphere evenly by height, with some variation by the wavelength/energy regime. However, the atmosphere heats up at lower altitudes while cooling higher. This is the expected pattern if the temperature of a greenhouse gas pushes, as in Venus.
Theory of solar variation
A US study in 1994 concluded that TSI variations are the most likely cause of significant climate change in the pre-industrial era, before significant human-produced carbon dioxide enters the atmosphere.
Scafetta and west-corrected solar proxy data and lower tropospheric temperatures for pre-industrial era, prior to significant anthropogenic greenhouse concentration, suggesting that TSI variations may have contributed 50% of the observed heating between 1900 and 2000 (although they concluded "our estimates of the effects of the sun on climate may be excessive and should be regarded as upper limits.") This contrasts with the results of global climate models that predict solar power from climate through direct radiation imposition is too small to account for significant contributions.
In 2000, Stott and others reported the most comprehensive model simulations of 20th century climate on that date. Their study looked at "natural amplifying agents" (solar variations and volcanic emissions) and "anthropogenic imposition" (greenhouse gases and aerosol sulphates). They found that "solar effects may have contributed significantly to warming in the first half of the century, although these results depend on the reconstruction of total solar radiation used.In the second half of this century, we found that anthropogenic increases in greenhouse gases were largely responsible over observed heating, offset by some cooling due to anthropogenic aerosol sulfate, without evidence of significant solar effect. "Stott's group found that combining these factors allowed them to simulate global temperature changes throughout the 20th century. They predict that sustainable greenhouse gas emissions will lead to future temperature increases "at levels similar to those observed in recent decades". In addition, the study notes "the uncertainty in the history of forcing" - in other words, forcing the past may still have a delayed warming effect, most likely because of the oceans.
Stott's work in 2003 largely revised his judgment, and found significant solar contributions to recent warming, although still smaller (between 16 and 36%) than greenhouse gases.
A study in 2004 concluded that solar activity affects climate - based on sunspot activity, but only plays a small role in current global warming.
Correlation with solar cycle length
In 1991, Friis-Christensen and Lassen claimed a strong correlation of the length of the solar cycle with changes in the temperature of the northern hemisphere. They initially used sunspot and temperature measurements from 1861 to 1989 and then extended the period using four centuries of climate records. Their relationship is reported to emerge to account for nearly 80 percent of the temperature changes measured during this period. The mechanism behind this claimed correlation is a matter of speculation.
In a 2003 Sea paper identified a problem with some of these correlation analyzes. Damon and the Sea claim:
the apparent strong correlation shown on this graph is obtained by faulty handling of physical data. Graphics are still widely mentioned in the literature, and their misleading characters have not been generally recognized.
Damon and the Sea states that when the graph is corrected to filter errors, the recent sensational agreement with global warming, which attracts the world's attention, is completely gone.
In 2000, Lassen and Thejll updated their 1991 study and concluded that while the solar cycle accounted for about half the temperature rise since 1900, it failed to explain the 0.4 Â ° C rise since 1980. The 2005 Benestad review found that the solar cycle did not follow Earth's global average surface temperature.
Weather
Sun activity can also affect regional climates, such as for the river ParanÃÆ'¡ and Po. Measurements from the Sun Radiation and NASA Climate Experiments show that solar UV output is more variable than total solar radiation. Climate modeling shows that low solar activity can lead to, for example, winters colder in the US and northern Europe and milder winters in Canada and southern Europe, with slight changes in global averages. More broadly, relationships have been suggested between the solar cycle, global climate and regional events such as El Nià ± o. Hancock and Yarger found "statistically significant associations between multiple sunspot cycles [~ 21 years] and the phenomenon of 'January melting along the East Coast and between the sunspot cycle of double and' drought '(temperature and rainfall June) in the Midwest."
Cloud condensation
A recent study at the CERN CLOUD facility examined the relationship between cosmic rays and cloud condensation nuclei, demonstrating the effects of high-energy particulate radiation in the nucleation of aerosol particles that are precursors to cloud condensation nuclei. Kirby (CLOUD team leader) said, "At the moment, it [experiment] actually does not say anything about the possible effects of cosmic rays on clouds and climate." Following further investigation, the team concluded that "variations in the intensity of cosmic rays do not affect the climate through nucleation."
1983-1994 global low cloud forming data from the International Satellite Clouds Climatology Project (ISCCP) is highly correlated with the flux cosmic flux (GCR) flux; after this period, the correlation is broken. 3-4% changes in turbidity and concurrent changes in upper cloud temperatures correlate with the solar and sunspots of 11 and 22 years, with an increase in GCR levels during the "antiparallel" cycle. The change in global average cloud cover is measured at 1.5-2%. Several GCR studies and cloud cover studies found positive correlations at latitudes greater than 50 Â ° and negative correlations at low latitudes. However, not all scientists accept this correlation as statistically significant, and some that relate it to other solar variability ( eg. UV or total radiation variation) rather than directly to GCR changes. The difficulty in interpreting these correlations includes the fact that many aspects of solar variability change at the same time, and some climate systems have a delayed response.
Historical perspective
Physicist and historian Spencer R. Weart in The Discovery of Global Warming (2003) writes:
The study of the [sunspot] cycle is generally popular in the first half of the century. The government has collected a lot of weather data to play and inevitably one finds a correlation between the sunspot cycle and choosing weather patterns. If the rain in England does not fit the cycle, there might be a storm in New England. Respected scientists and enthusiastic amateurs insist that they have found enough credible patterns to make predictions. Sooner or later even if each prediction fails. An example is a very credible prediction about the dry season in Africa during the initial minimum fire point of the 1930s. As the period became wet, a meteorologist then recalled "the problem of sunspots and weather ties fell into disagreement, especially among British meteorologists who witnessed the disruption of some of their most respected superiors." Even in the 1960s he said, "For young [climate] researchers to entertain every sun-weather expression statement is by its own brand of cranks."
See also
- Radiative forces
- Sun phenomenon
- The solar cycle
- Sun observation
References
General reference
- "The Role of the Sun in Climate Change" (PDF) . Proc. International Conference on Global Warming and the Next Ice Age, 19-24 August 2001, Halifax, Nova Scotia . Archived from the original (PDF) on October 22, 2004 . Obtained 2005-02-21 .
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White, Warren B.; Lean, Judith; Cayan, Daniel R.; Dettinger, Michael D. (1997). "Response of global upper ocean temperatures to changes in solar radiation". Journal of Geophysical Research . 102 (C2): 3255-66. Bibcode: 1997JGR... 102.3255W. doi: 10.1029/96JC03549. - A graphical representation of the relationship between natural and anthropogenic factors that contribute to climate change appears in "Climate Change 2001: Scientific Basis", a report by the Intergovernmental Panel on Climate Change (IPCC).
External links
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Gerrit Lohmann; Norel Rimbu; Mihai Dima (2004). "Climatic signs of variations in solar radiation: analysis of instrumental data, historical, and long-term proxies". International Journal of Climatology . 24 (8): 1045-56. Bibcode: 2004IJCli..24.1045L. doi: 10.1002/joc.1054. Ã,
Source of the article : Wikipedia
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