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Terrestrial Ecosystem Interactions with Global Climate and Socio-Economics

Ahlström, Anders LU (2013)
Abstract (Swedish)
Popular Abstract in Swedish

Den globala landbaserade kolcykeln reglerar mängden växthusgaser i atmosfären. För närvarande tas varje år 25-30% av våra utsläpp upp av de landbaserade ekosystemen vilket är en viktig ekosystemtjänst som kanske inte kommer att bestå i längden. Upptagskapaciteten av både hav och landbaserade ekosystem tenderar att försvagas av global uppvärmning. Detta leder till att en större andel av våra utsläpp stannar i atmosfären och bidrar till uppvärmning, vilket i sin tur ytterligare försvagar kolcykelns upptagsförmåga.

Här projiceras och analyseras historiska, nuvarande och framtida variationer i och drivkrafter bakom kolutbytet av landbaserade ekosystem. Osäkerheter och robusta mönster och... (More)
Popular Abstract in Swedish

Den globala landbaserade kolcykeln reglerar mängden växthusgaser i atmosfären. För närvarande tas varje år 25-30% av våra utsläpp upp av de landbaserade ekosystemen vilket är en viktig ekosystemtjänst som kanske inte kommer att bestå i längden. Upptagskapaciteten av både hav och landbaserade ekosystem tenderar att försvagas av global uppvärmning. Detta leder till att en större andel av våra utsläpp stannar i atmosfären och bidrar till uppvärmning, vilket i sin tur ytterligare försvagar kolcykelns upptagsförmåga.

Här projiceras och analyseras historiska, nuvarande och framtida variationer i och drivkrafter bakom kolutbytet av landbaserade ekosystem. Osäkerheter och robusta mönster och deras orsaker undersöks. Det visas att variationer så som torra perioder påverkar det globala utbytet av kol signifikant, trotts att de inträffar i begränsade regioner. Förändringar under säsongen kan förändra balansen mellan upptag och utsläpp av kol genom att stimulera nedbrytningen av kol i marken som dominerar under höst och vinter mer än upptaget av kol genom fotosyntes under växtsäsongen. Dessa variationer kan vara viktigare för kolcykeln än global trender där de drivande variablerna förändras långsamt.

Ekosystemmodeller representerar kraftfulla verktyg som kan öka vår kunskap om hur ekosystem fungerar. Dessutom möjliggör de projektioner av framtida förändringar i ekosystem och i kolcykeln. I denna avhandling demonstreras det att ekosystemmodeller generellt fångar globala fördelningarna av kolutbyte och dess variationer över tid. Dock är framtida projektioner omgivna av osäkerhet, ett resultat av en kombination av skillnader mellan klimatprojektioner och osäkerheter i hur ekosystem svarar på förändringar i klimatet. Här visas att osäkerheter associerade med skillnader mellan klimatmodeller är större än osäkerheten som olika scenarier av framtida växthusgaskoncentrationer medför. Variationer i havsytetemperaturer i klimatmodeller, och då speciellt de som beror på El Niño-Southern Oscillation, framstår som speciellt viktiga för korrekta uppskattningar av framtida kolutbyte.

Mänskliga aktiviteter bidrar genom att tillföra en väsentlig mängd kol till kolcykeln. Klimat-ekonomi modeller har potential att bistå med mått som är direkt relevanta för politiker och lagstiftare för att minska klimatförändringarna. Här demonstreras vikten av en korrekt representation av klimatsystemet och kolcykeln i klimatekonomimodeller för korrekta uppskattningar av framtida ekonomi och klimatets påverkan på denna. (Less)
Abstract
The global terrestrial carbon cycle plays a pivotal role in regulating the atmospheric composition of greenhouse gases. Currently it is responsible for removing 25-30% of our emissions every year, an important ecosystem service that may not persist in the long term. Global warming tends to decrease the CO2 sink capacity of the world’s oceans and ecosystems leading to a larger fraction of our emissions remaining in the atmosphere contributing to further warming, which in turn further decreases the sink capacity.

Here past, present and future variations and drivers of terrestrial ecosystem fluxes are analysed and projected. Uncertainties and robustness as well as their origin are assessed. It is shown that short term variations... (More)
The global terrestrial carbon cycle plays a pivotal role in regulating the atmospheric composition of greenhouse gases. Currently it is responsible for removing 25-30% of our emissions every year, an important ecosystem service that may not persist in the long term. Global warming tends to decrease the CO2 sink capacity of the world’s oceans and ecosystems leading to a larger fraction of our emissions remaining in the atmosphere contributing to further warming, which in turn further decreases the sink capacity.

Here past, present and future variations and drivers of terrestrial ecosystem fluxes are analysed and projected. Uncertainties and robustness as well as their origin are assessed. It is shown that short term variations such as droughts significantly influence global fluxes even though occurring in limited regions. Additionally, seasonal changes may alter the present balance between uptake and release of carbon by stimulating the process of release of carbon through respiration dominating in the winter more than the photosynthesis and net uptake of carbon in the growing season. These variations may be more important for the carbon cycle than long term trends.

Ecosystem models represents powerful tools to further our understanding of the functioning of terrestrial ecosystems as well as allowing for projections of the potential future evolution of the carbon cycle. It is demonstrated that ecosystem models generally capture the main global spatial and temporal distributions of carbon fluxes. However, future projections are accompanied by large uncertainties, a result of a combination of uncertainties in climate predictions by climate models and uncertainties in the response of ecosystems to changes in the drivers. It is shown that uncertainties arising from differences in climate projections in terms of seasonal changes and short term variability dominate uncertainties arising from different scenarios of future atmospheric CO2 concentrations. Additionally, representation of sea surface temperature variations and especially variations associated with El Niño-Southern Oscillation in climate models stands out as particularly important for accurate predictions of future carbon fluxes.

Human activity contributes with a significant perturbation of the carbon-cycle and the climate system. Climate-economy models have the potential to supply direct policy-relevant estimates for climate mitigation. Here it is demonstrated that correct representation of the climate system and the carbon cycle in climate-economy models is important for making accurate estimates of future economy. (Less)
Please use this url to cite or link to this publication:
author
supervisor
opponent
  • Reichstein, Markus, Max-Planck-Institute for Biogeochemistry Jena
organization
publishing date
type
Thesis
publication status
published
subject
publisher
Department of Physical Geography and Ecosystem Science, Lund University
defense location
Världen, Geocentrum
defense date
2013-04-26 13:00
ISBN
978-91-85793-32-7
project
BECC
MERGE
language
English
LU publication?
yes
id
e56810b6-b06a-470a-8a96-64a7971a06a8 (old id 3629056)
date added to LUP
2013-04-10 16:58:33
date last changed
2016-09-19 08:45:06
@misc{e56810b6-b06a-470a-8a96-64a7971a06a8,
  abstract     = {The global terrestrial carbon cycle plays a pivotal role in regulating the atmospheric composition of greenhouse gases. Currently it is responsible for removing 25-30% of our emissions every year, an important ecosystem service that may not persist in the long term. Global warming tends to decrease the CO2 sink capacity of the world’s oceans and ecosystems leading to a larger fraction of our emissions remaining in the atmosphere contributing to further warming, which in turn further decreases the sink capacity. <br/><br>
Here past, present and future variations and drivers of terrestrial ecosystem fluxes are analysed and projected. Uncertainties and robustness as well as their origin are assessed. It is shown that short term variations such as droughts significantly influence global fluxes even though occurring in limited regions. Additionally, seasonal changes may alter the present balance between uptake and release of carbon by stimulating the process of release of carbon through respiration dominating in the winter more than the photosynthesis and net uptake of carbon in the growing season. These variations may be more important for the carbon cycle than long term trends. <br/><br>
Ecosystem models represents powerful tools to further our understanding of the functioning of terrestrial ecosystems as well as allowing for projections of the potential future evolution of the carbon cycle. It is demonstrated that ecosystem models generally capture the main global spatial and temporal distributions of carbon fluxes. However, future projections are accompanied by large uncertainties, a result of a combination of uncertainties in climate predictions by climate models and uncertainties in the response of ecosystems to changes in the drivers. It is shown that uncertainties arising from differences in climate projections in terms of seasonal changes and short term variability dominate uncertainties arising from different scenarios of future atmospheric CO2 concentrations. Additionally, representation of sea surface temperature variations and especially variations associated with El Niño-Southern Oscillation in climate models stands out as particularly important for accurate predictions of future carbon fluxes.<br/><br>
Human activity contributes with a significant perturbation of the carbon-cycle and the climate system. Climate-economy models have the potential to supply direct policy-relevant estimates for climate mitigation. Here it is demonstrated that correct representation of the climate system and the carbon cycle in climate-economy models is important for making accurate estimates of future economy.},
  author       = {Ahlström, Anders},
  isbn         = {978-91-85793-32-7},
  language     = {eng},
  publisher    = {ARRAY(0xa08118)},
  title        = {Terrestrial Ecosystem Interactions with Global Climate and Socio-Economics},
  year         = {2013},
}