Molnens påverkan på jordens strålningsbalans och klimatsystem
(2022) In Examensarbeten i geologi vid Lunds universitet GEOL01 20221Department of Geology
- Abstract
- The role of clouds in the climate system has been studied and their impact on the Sun's impact on the Earth's energy balance. The Earth's albedo affects the energy balance by influencing how much of the Sun’s radiation is reflected or absorbed. Clouds affect the Earth's albedo and therefore play an important role in this balance. Cloud formation occurs almost 100% in the troposphere and everything we call weather takes place there. Clouds form when warm moist air rises in the atmosphere and condenses. There are a variety of types of clouds, low so-called "Warm clouds" e.g. cumulus clouds up to 2-4 km, which consists only of water droplets and there are high "cold clouds" above about 8-12 km such as cirrocumulus, which consists only of ice... (More)
- The role of clouds in the climate system has been studied and their impact on the Sun's impact on the Earth's energy balance. The Earth's albedo affects the energy balance by influencing how much of the Sun’s radiation is reflected or absorbed. Clouds affect the Earth's albedo and therefore play an important role in this balance. Cloud formation occurs almost 100% in the troposphere and everything we call weather takes place there. Clouds form when warm moist air rises in the atmosphere and condenses. There are a variety of types of clouds, low so-called "Warm clouds" e.g. cumulus clouds up to 2-4 km, which consists only of water droplets and there are high "cold clouds" above about 8-12 km such as cirrocumulus, which consists only of ice crystals. There are also clouds like altocumulus in between that contain a mixture of water droplets and ice crystals. What they all have in common is that they reflect solar radiation and at the same time they absorb heat from the Earth’s own radiation.
Cloud formation and the processes behind it are therefore of great interest. In order for clouds to form, the relative humidity, RH, is required to be above 100%: Under real conditions, neither water droplets nor ice crystals can form if no aerosol particles are present. Aerosols act as nuclei on which water or ice can grow. The composition of aerosols is very complex and not fully understood. They are formed for natural reasons as e.g. from the oceans that create aerosols of various salts from the winds, as well as e.g. of pollen from forests and forest fires. Anthropogenic aerosols from industries and transports that emit large amounts of soot particles that act as condensation nuclei also affect cloud formation.
During the last 25 years or so, cosmic radiation has also been studied as a cause of cloud formation and much attention arose when a research group claimed that all global warming during the 20th century could be attributed to this effect. Through various studies, attempts have been made to investigate the magnitude of the effect of cosmic radiation, but without conclusive results. However, the effect seems to be far too small to explain the global warming that has taken place since the middle of the 19th century.
The IPCC's latest and best future projections for the temperature increase up to the year 2100 are between about 1.5 oC to 4.5 oC. This is partly depending on which “confidence level” is chosen (in the climate model used) or which so-called RCP - "Representative Concentration Pathway", i.e. which emission scenario (of CO2) is considered. However, this large difference is also due to the fact that cloud formation and aerosols and their feedback effects on the energy balance are poorly understood. A better understanding of these processes could reduce the large difference in the IPCC's future projections of the temperature increase to 2100. (Less) - Abstract (Swedish)
- Molnens roll i klimatsystemet har studerats och deras påverkan på solens inverkan på jordens energibalans. Jordens albedo påverkar energibalansen genom att den påverkar hur mycket av solens instrålning som reflekteras eller absorberas. Moln påverkar jordens albedo och spelar därför en viktig roll i denna balans. Molnbildning sker till nära 100% i troposfären och där finns allt det vi kallar väder. Moln bildas när varm fuktig luft stiger upp i atmosfären och kondenserar. Det finns en mängd olika typer av moln, låga s.k. ”varma moln” som cumulus-moln upp till 2-4 km, som består enbart av vattendroppar och det finns höga ”kalla moln” över ca 8-12 km, som cirrocumulus som består enbart av iskristaller. Det finns även moln som altocumulus... (More)
- Molnens roll i klimatsystemet har studerats och deras påverkan på solens inverkan på jordens energibalans. Jordens albedo påverkar energibalansen genom att den påverkar hur mycket av solens instrålning som reflekteras eller absorberas. Moln påverkar jordens albedo och spelar därför en viktig roll i denna balans. Molnbildning sker till nära 100% i troposfären och där finns allt det vi kallar väder. Moln bildas när varm fuktig luft stiger upp i atmosfären och kondenserar. Det finns en mängd olika typer av moln, låga s.k. ”varma moln” som cumulus-moln upp till 2-4 km, som består enbart av vattendroppar och det finns höga ”kalla moln” över ca 8-12 km, som cirrocumulus som består enbart av iskristaller. Det finns även moln som altocumulus däremellan som innehåller en blandning av vattendroppar och iskristaller. Alla har de gemensamt att de reflekterar solinstrålning och samtidigt som de tar upp värme från jordens egenutstrålning.
Molnbildning och de processer som ligger bakom är därför av stort intresse. För att moln ska bildas krävs att den relativa fuktigheten, RH, är över 100%: Under verkligt förhållande kan inte vare sig vattendroppar eller iskristaller bildas om det inte finns partiklar i form av aerosoler närvarande. Aerosoler verkar som kärnor som vatten eller is kan växa på. Sammansättningen av aerosoler är mycket komplex och inte till fullo förstådd. De bildas av naturliga skäl som t.ex. från haven som skapar aerosoler av olika salter som blåser upp, likaväl som t.ex. av pollen från skogar och skogsbränder. Även antropogena aerosoler från industrier och transporter som släpper ut mängder av sotpartiklar som fungerar som kondensationskärnor påverkar molnbildning.
Under de senaste ca 25 åren har även kosmisk strålning studerats som orsak till molnbildning och mycket uppmärksamhet uppstod då en forskargrupp hävdade att all global uppvärmning under 1900-talet skulle kunna hänföras till denna effekt. Man har genom olika studier försökt undersöka hur stor effekten av den kosmiska strålningen är men utan konklusivt resultat. Dock tycks effekten vara alldeles för liten för att kunna förklara den globala uppvärmningen som skett sen mitten av 1800-talet.
IPCCs senaste och bästa framtidsprojektioner för temperaturökningen fram till år 2100 är mellan
ca 1,5 oC till 4,5 oC. Detta är delvis beroende på vilken konfidensnivå som väljs ( i den klimatmodell som används) eller vilket s.k. RCP - ”Representative Concentration Pathway”, dvs. vilket utsläppsscenario (av CO2) som betraktas. Men, denna stora skillnad beror också på att molnbildning och aerosoler och deras feedback-effekter på energibalansen är dåligt förstådda. En bättre förståelse för dessa processer skulle kunna minska den stora skillnaden i IPCCs framtida projektioner om temperaturökningen till år 2100. (Less) - Popular Abstract (Swedish)
- I dagens klimatdebatt talas det dagligen om koldioxidens och i allt större utsträckning om metanets inverkan på klimatet eftersom de är starka växthusgaser. Detta gör man trots att de utgör en mycket ringa andel av atmosfären, och endast finns i vad man kallar spårmängder, 0,0419% respektive 0,00018 % . Man har då totalt utelämnat betydelsen av vattnets närvaro genom moln och luftfuktighet , som också ger en stark växthuseffekt och som utgör 0,25% i medeltal. Det vill säga, atmosfären består till ~99,7% av icke-växthusgaser.
Please use this url to cite or link to this publication:
http://lup.lub.lu.se/student-papers/record/9088007
- author
- Jägfeldt, Hans LU
- supervisor
- organization
- alternative title
- The impact of clouds on the Earth’s radiation balance and climate system
- course
- GEOL01 20221
- year
- 2022
- type
- M2 - Bachelor Degree
- subject
- keywords
- moln, kondensation, aerosol, strålningsbalans, klimat, klimatsystem, kosmisk strålning, troposfären
- publication/series
- Examensarbeten i geologi vid Lunds universitet
- report number
- 641
- language
- Swedish
- id
- 9088007
- date added to LUP
- 2022-06-14 14:35:56
- date last changed
- 2022-06-14 14:35:56
@misc{9088007,
abstract = {{The role of clouds in the climate system has been studied and their impact on the Sun's impact on the Earth's energy balance. The Earth's albedo affects the energy balance by influencing how much of the Sun’s radiation is reflected or absorbed. Clouds affect the Earth's albedo and therefore play an important role in this balance. Cloud formation occurs almost 100% in the troposphere and everything we call weather takes place there. Clouds form when warm moist air rises in the atmosphere and condenses. There are a variety of types of clouds, low so-called "Warm clouds" e.g. cumulus clouds up to 2-4 km, which consists only of water droplets and there are high "cold clouds" above about 8-12 km such as cirrocumulus, which consists only of ice crystals. There are also clouds like altocumulus in between that contain a mixture of water droplets and ice crystals. What they all have in common is that they reflect solar radiation and at the same time they absorb heat from the Earth’s own radiation.
Cloud formation and the processes behind it are therefore of great interest. In order for clouds to form, the relative humidity, RH, is required to be above 100%: Under real conditions, neither water droplets nor ice crystals can form if no aerosol particles are present. Aerosols act as nuclei on which water or ice can grow. The composition of aerosols is very complex and not fully understood. They are formed for natural reasons as e.g. from the oceans that create aerosols of various salts from the winds, as well as e.g. of pollen from forests and forest fires. Anthropogenic aerosols from industries and transports that emit large amounts of soot particles that act as condensation nuclei also affect cloud formation.
During the last 25 years or so, cosmic radiation has also been studied as a cause of cloud formation and much attention arose when a research group claimed that all global warming during the 20th century could be attributed to this effect. Through various studies, attempts have been made to investigate the magnitude of the effect of cosmic radiation, but without conclusive results. However, the effect seems to be far too small to explain the global warming that has taken place since the middle of the 19th century.
The IPCC's latest and best future projections for the temperature increase up to the year 2100 are between about 1.5 oC to 4.5 oC. This is partly depending on which “confidence level” is chosen (in the climate model used) or which so-called RCP - "Representative Concentration Pathway", i.e. which emission scenario (of CO2) is considered. However, this large difference is also due to the fact that cloud formation and aerosols and their feedback effects on the energy balance are poorly understood. A better understanding of these processes could reduce the large difference in the IPCC's future projections of the temperature increase to 2100.}},
author = {{Jägfeldt, Hans}},
language = {{swe}},
note = {{Student Paper}},
series = {{Examensarbeten i geologi vid Lunds universitet}},
title = {{Molnens påverkan på jordens strålningsbalans och klimatsystem}},
year = {{2022}},
}