Global blackout

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The global dimming (English global dimming is) a world looked turbidity of the atmosphere , as a result, the intensity of the sunlight that the Earth's surface reaches decreases. The causes are suspended matter , especially sulphate aerosols and soot , contrails from aircraft and dust from volcanic eruptions or coal fires .

Measurement and development

Since the 1950s, hundreds of measuring stations have been installed from the Arctic to the Antarctic to measure solar radiation. In the mid-1980s, Atsumu Ōmura ( Eidgenössische Technische Hochschule Zürich ) was evaluating the data. His comments on “Global Dimming” were only hesitantly received by experts. The global darkening effect has also been documented in Israel by Gerald Stanhill , an English researcher. He compared radiation measurements from 1950 to the 1980s. Based on the measurement of the potential evaporation using an evaporimeter (Class A Pan) it was discovered that the annual amount of evaporation of water has decreased worldwide.

Another series of measurements in the Indian Ocean in 1999 showed that air pollution seems to play a major role in global darkening. There, scientists measured 10 percent less solar radiation in areas with high air pollution than in areas with clean air.

From 1961 to 1990, solar radiation on the earth's surface decreased by an estimated 4 percent. This value is subject to significant regional differences. The highest darkening over the USA was measured at 10 percent. Since the late 1980s, solar radiation measured in Europe and the USA has tended to increase again, while it has continued to decrease in China.

Reasons and Effects

A satellite photo of Nova Scotia shows numerous contrails from jet planes traveling between the east coast of the United States and Europe .

It is currently assumed that this effect is mainly due to the increased concentration of aerosols in the earth's atmosphere . These arise when organic matter ( wood , coal , oil , gas ) is burned . Accordingly, the most important focal points would be the major industrial nations in Asia, North America and Europe. But burning oil wells in Kuwait or slash and burn of the rainforest in Brazil are also possible causes.

Some climate researchers had hypothesized that the contrails caused by airplanes contribute to global blackout; However, the constant air traffic never allowed a verification of the hypothesis. After the terrorist attacks of September 11, 2001 , a three-day flight ban was in effect for the entire United States . During this time it was observed that the difference between the highest daytime temperature and the lowest nighttime temperature over the USA was 1.1 ° C higher than the mean for the years 1971-2000, while it was just below it in the three days before the flight ban the flight ban even almost 1 ° C below. There was such a large difference in the daily air temperature for days 11-14. September has not been measured in the past thirty years. According to the German Aerospace Center DLR , the contrails of air traffic contribute 0.1% to global cloud cover.

On the one hand, the emitted aerosols reflect the sunlight, and on the other, the water condenses on them - just like on natural particles (e.g. dust or ice) - and clouds form . Due to the high number of aerosols generated by humans, more droplets form, but they are also smaller. These clouds are longer and reflect the higher albedo sunlight even more into the All . Less sunlight means, on the one hand, a cooling of the atmosphere, and on the other hand, less evaporation on the ground and therefore less precipitation . The ground is more humid, there are more clouds, but it still rains less. These effects can lead to droughts in the direction of the wind. There is a correlation between the amount of aerosols from emissions and droughts in the Sahel zone .

Link to global warming

Global darkening counteracts global warming . While global darkening cools the climate through reflection of the sun's rays , greenhouse gases such as water vapor, CO 2 , methane and CFCs heat the atmosphere. With the increasing filtering of exhaust gases in the world, global darkening has been decreasing again since the mid-1980s. However, global warming continues to rise due to the increased energy consumption of people - the global average temperature rose by 0.76 ° C between 1906 and 2005.

The global darkening has dampened the previous extent of the greenhouse effect due to its cooling effect, the extent of which has not yet been precisely quantified. It is not known exactly to what extent global warming is affected by the global eclipse. For the period from 1940 to 1975, according to the current state of knowledge, an increase in the albedo caused by aerosol emissions superimposed the warming effect caused by greenhouse gas emissions and caused the earth's surface temperatures to stagnate.

If successful measures are taken to combat global darkening - reducing particle emissions through filters, etc. - and thereby eliminating their cooling effect, this could mean that the previously predicted extent of global warming will be exceeded.

Artificial darkening in the atmosphere is being discussed as a possible emergency measure to reduce global warming under the name of Solar Radiation Management as part of geoengineering. To this end, Harvard University began planning the SCoPEx experiment in 2018, in which calcium carbonate particles are to be released at a height of 20 km ( stratosphere ) over the southwestern United States.

Related topics

  • A volcanic winter can be triggered by volcanic global darkening.
  • A nuclear winter could be the result of a global nuclear war.
  • With light pollution refers to the nightly illumination of the sky by anthropogenic light sources.
  • According to the “ chemtrails ” conspiracy theory , the atmosphere is deliberately enriched with particles from airplanes, which are said to have (depending on the variant, different) effects on people and nature.

Web links

Individual evidence

  1. ↑ a b c global dimming . In: John A. Matthews (Ed.): Encyclopedia of Environmental Change . SAGE, 2013, ISBN 978-1-4462-6488-1 (English).
  2. ^ Beate G. Liepert: Observed Reductions in Surface Solar Radiation in the United States and Worldwide from 1961 to 1990 . In: Geophysical Research Letters . tape 29 , no. 10 , 2002, doi : 10.1029 / 2002GL014910 (English, ldeo.columbia.edu [PDF; 172 kB ]).
  3. ↑ Yanyi Hey, Kaicun Wang, Zhou Chunlüe and Martin Wild: A Revisit of Global Dimming and Brightening Based on the Sunshine duration . In: Geophysical Research Letters . April 2018, doi : 10.1029 / 2018GL077424 (English).
  4. ↑ David J. Travis, Andrew M. Carleton, Ryan G. Lauritsen: Contrails reduce daily temperature range . In: Nature . August 8, 2002, doi : 10.1038 / 418601a (English).
  5. ↑ Susanne Marquart: Climate Impact of Contrails: Investigations with a Global Atmospheric Circulation Model. Research Report 2003-16; uni-muenchen.de (PDF; 7.7 MB)
  6. ^ Richard K. Snow, Mary M. Snow: Ethopia . In: S. George Philander (Ed.): Encyclopedia of Global Warming and Climate Change . SAGE, 2012, ISBN 978-1-4129-9261-9 , Global Dimming and Famine (English).
  7. ↑ Monika Thakur: Global Dimming and Global Warming: Dangerous Alliance . In: Tanu Jindal (Ed.): Paradigms in Pollution Prevention (=  SpringerBriefs in Environmental Science ). 2018, doi : 10.1007 / 978-3-319-58415-7 .
  8. ↑ We can't treat global browning as a standalone issue . New Scientist , Jan. 26, 2016
  9. ↑ Armin Frey, Thomas Jäger, Dirk Messner, Manfred Fischedick, Thomas Hartmann-Wendels: Globalization and international agreements . Springer-Verlag, 2013, p. 73 books.google.de
  10. ↑ Stefan Rahmstorf : The theses of the "climate skeptics" - what is it? One answer to Alvo von Alvensleben . Potsdam Institute for Climate Impact Research , September 2004
  11. ↑ Yangyang Xu, Veerabhadran Ramanathan, David G. Victor: Global warming will happen faster than we think . In: Nature . tape 564 , no. 7734 , December 5, 2018, p. 30–32 , doi : 10.1038 / d41586-018-07586-5 ( nature.com [accessed October 9, 2019]).
  12. ↑ BH Samset, M. Sand, CJ Smith, SE Bauer, PM Forster: Climate Impacts From a Removal of Anthropogenic Aerosol Emissions . In: Geophysical Research Letters . tape 45 , no. 2 , January 8, 2018, ISSN  1944-8007 , p. 1020-1029 , doi : 10.1002 / 2017GL076079 ( wiley.com [accessed October 9, 2019]).
  13. ^ First sun-dimming experiment will test a way to cool Earth . nature.com, November 27, 2018
  14. ↑ Harvard creates advisory panel to oversee solar geoengineering project . nature.com, July 30, 2019