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Are solar activity and cosmic rays important factors behind climate change?

Löfroth, Elin (2008) In Dissertations in Geology at Lund University
Department of Geology
Abstract
The solar influence on climate is a hot topic in today’s climate debate and constitutes one of the largest
uncertainties in our knowledge about the climate system. There are several ways in which solar activity changes
could affect climate. One of the suggested links between solar activity and climate is an influence from galactic
cosmic rays (GCR) on the formation of low clouds. Because of the net cooling effect of low clouds an increased
GCR influx would lead to more low clouds forming and have a cooling effect on climate, whereas a decrease would
lead to a warmer climate. This theory has gained much attention in the media because of its implications for our
knowledge of the climate system and its importance for the Climate Change... (More)
The solar influence on climate is a hot topic in today’s climate debate and constitutes one of the largest
uncertainties in our knowledge about the climate system. There are several ways in which solar activity changes
could affect climate. One of the suggested links between solar activity and climate is an influence from galactic
cosmic rays (GCR) on the formation of low clouds. Because of the net cooling effect of low clouds an increased
GCR influx would lead to more low clouds forming and have a cooling effect on climate, whereas a decrease would
lead to a warmer climate. This theory has gained much attention in the media because of its implications for our
knowledge of the climate system and its importance for the Climate Change debate.
This report reviews literature on the GCR-low cloud hypothesis. The scientific basis of the hypothesis is
presented as well as previous investigations concerning correlations between GCR, solar activity and low
clouds/climate. These studies are based on proxies for solar activity as well as satellite measurements of low clouds
and geological proxies for climate. Because of the longer time-scales of geological archives they are a good basis
for investigation of GCR and solar influence on climate. Furthermore, criticisms against the theory are reviewed
and discussed.
It is concluded that there is no solid evidence for the claimed link between GCR and low clouds. There are
correlations between GCR and climate, but the synchronization in geological archives is not always good and there
are also other possible links between the Sun and climate. (Less)
Abstract (Swedish)
Solens påverkan på klimatet är ett hett ämne i dagens klimatdebatt och utgör en av de största
osäkerheterna i vår kunskap om klimatsystemet. Det finns flera sätt som förändringar i solaktivitet skulle kunna
påverka klimatet på. En av de föreslagna länkarna mellan solaktivitet och klimat är att den galaktiska kosmiska
strålningen (GCR) påverkar bildningen av låga moln. På grund av att låga moln har en kylande effekt på klimatet
skulle en ökning av GCR ge ett kallare klimat, emedan en minskning skulle innebära ett varmare klimat. Teorin har
blivit mycket uppmärksammad i media på grund av dess implikationer för vår kunskap om klimatsystemet och därför
av betydelse för klimatdebatten.
I den här uppsatsen presenteras litteratur som... (More)
Solens påverkan på klimatet är ett hett ämne i dagens klimatdebatt och utgör en av de största
osäkerheterna i vår kunskap om klimatsystemet. Det finns flera sätt som förändringar i solaktivitet skulle kunna
påverka klimatet på. En av de föreslagna länkarna mellan solaktivitet och klimat är att den galaktiska kosmiska
strålningen (GCR) påverkar bildningen av låga moln. På grund av att låga moln har en kylande effekt på klimatet
skulle en ökning av GCR ge ett kallare klimat, emedan en minskning skulle innebära ett varmare klimat. Teorin har
blivit mycket uppmärksammad i media på grund av dess implikationer för vår kunskap om klimatsystemet och därför
av betydelse för klimatdebatten.
I den här uppsatsen presenteras litteratur som behandlar hypotesen om ett samband mellan GCR och låga
moln. Hypotesens vetenskapliga grund presenteras tillsammans med tidigare studier av korrelationer mellan GCR,
solaktivitet och låga moln/klimatet. Dessa undersökningar grundas på proxydata för solaktivitet, satellitmätningar
av låga moln samt geologiska proxydata för klimatet. På grund av de längre tidsskalorna i geologiska arkiv ger dessa
ett bra underlag för att studera påverkan från GCR och solaktivitet på klimatet. Vidare presenteras och diskuteras
den kritik som framförts mot hypotesen.
Sammanfattningsvis menar jag att det inte finns starka bevis för den påstådda länken mellan GCR och låga
moln. Korrelationer mellan GCR och klimatet existerar, men synkroniseringen mellan dessa i geologiska arkiv är
inte alltid så bra och det finns alternativa förklaringar till kopplingarna mellan solen och klimatet. (Less)
Please use this url to cite or link to this publication:
author
Löfroth, Elin
supervisor
organization
alternative title
Är solaktivitet och kosmisk strålning viktiga faktorer bakom klimatförändringar?
year
type
M2 - Bachelor Degree
subject
keywords
climate, galactic cosmic rays, low clouds, the Sun, klimat, galaktisk kosmisk strålning, låga moln, solen
publication/series
Dissertations in Geology at Lund University
report number
229
language
English
id
2303839
date added to LUP
2012-01-30 11:26:58
date last changed
2012-01-30 11:26:58
@misc{2303839,
  abstract     = {{The solar influence on climate is a hot topic in today’s climate debate and constitutes one of the largest
uncertainties in our knowledge about the climate system. There are several ways in which solar activity changes
could affect climate. One of the suggested links between solar activity and climate is an influence from galactic
cosmic rays (GCR) on the formation of low clouds. Because of the net cooling effect of low clouds an increased
GCR influx would lead to more low clouds forming and have a cooling effect on climate, whereas a decrease would
lead to a warmer climate. This theory has gained much attention in the media because of its implications for our
knowledge of the climate system and its importance for the Climate Change debate.
This report reviews literature on the GCR-low cloud hypothesis. The scientific basis of the hypothesis is
presented as well as previous investigations concerning correlations between GCR, solar activity and low
clouds/climate. These studies are based on proxies for solar activity as well as satellite measurements of low clouds
and geological proxies for climate. Because of the longer time-scales of geological archives they are a good basis
for investigation of GCR and solar influence on climate. Furthermore, criticisms against the theory are reviewed
and discussed.
It is concluded that there is no solid evidence for the claimed link between GCR and low clouds. There are
correlations between GCR and climate, but the synchronization in geological archives is not always good and there
are also other possible links between the Sun and climate.}},
  author       = {{Löfroth, Elin}},
  language     = {{eng}},
  note         = {{Student Paper}},
  series       = {{Dissertations in Geology at Lund University}},
  title        = {{Are solar activity and cosmic rays important factors behind climate change?}},
  year         = {{2008}},
}