Responsibility for past and future global warming: time horizon and non-linearities in the climate system
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Series / Report no.
Open Access
Type
Report
Language
en
Date
2003-01-15
Research Projects
Organizational Units
Journal Issue
Title
Responsibility for past and future global warming:
time horizon and non-linearities in the climate
system
Translated Title
Verantwoordlijkheid voor klimaatverandering:
tijdshorizon en niet-lineariteiten in het
klimaatsysteem
Published in
Abstract
Het Braziliaans voorstel om totale emissiereducties te
verdelen onder Annex-I landen is gebaseerd op een berekening van het
percentage dat elk land bijdraagt aan de totaal gerealiseerde
klimaatverandering. Dit rapport presenteert dergelijke berekeningen en
analyseert de invloed van de tijdshorizon van de emissies en
niet-lineariteiten in de mondiale koolstofcyclus. De analyse laat zien dat
naarmate de historische emissies vanaf een vroeger tijdstip worden
meegenomen de bijdrage van Annex-I regio's aan totale klimaatverandering in
2000 hoger wordt. Als het eindjaar verder in de toekomst wordt gekozen, dan
neemt de bijdrage van niet-Annex-I landen toe, vanwege sterk groeiende
emissies in de 21ste eeuw. Door het evaluatiejaar te kiezen later dan het
eindjaar van de emissies worden ook de vertraagde klimaateffecten van
emissies meegenomen. Hoe groter het gat tussen eindjaar en evaluatiejaar,
hoe meer de bijdrage van niet-Annex-I landen afneemt, met name door het
relatief grote aandeel van methaan in de totale emissies, met een korte
verblijftijd in de atmosfeer.Ons voorstel voor een nieuwe 'niet-lineaire',
maar transparante, methode om de bijdrage van landen aan de totale verhoogde
CO2 concentratie te berekenen verlaagt de bijdrage van Annex-I landen. Het
effect is groter dan dat van niet-lineariteit in stralingsforcering
(verzadiging), met tegengesteld teken. Aangezien het laatste effect
toeneemt in de tijd, heffen de twee effecten elkaar vrijwel op tegen het
eind van de 21ste eeuw. De analyse is uitgevoerd voor verschillende
aggregaties van landen binnen de klimaatconventie (Annex-I/non-Annex-I, 4
IPCC SRES regio's, of 17 kleinere RIVM IMAGE-regio's). Er bestaat
aanzienlijke heterogeniteit binnen geaggregeerde IPCC groepen, zodat
algemene conclusies met betrekking tot groepen als geheel niet gelden voor
elke kleinere emissie-eenheid (land) daarbinnen.
The Brazilian proposal for sharing the burden of emissions reductions among Annex-I Parties is based on the relative effect of a country's emissions on the global-mean surface-air temperature. This paper presents calculations of these relative effects, analysing the influence of the time horizon of emissions and of including non-linearities in the global carbon cycle. The analysis shows that an early start date for historical emissions increases the Annex-I contributions to global warming. Choosing an end date of emissions relatively late in time increases non-Annex-I contributions, giving more weight to their larger share in 21st century emissions. Delayed effects of global warming can be taken into account, if contributions are calculated some time after the emission end date. A calculation date long after the emission end date reduces non-Annex-I contributions, mainly because of their relative large share of relatively short-lived methane in total emissions. Our proposal for a new ('non-linear'), transparent approach for attributing CO2 concentrations generally increases non-Annex-I contributions. The impact is larger than that of including non-linearity in radiative forcing ('saturation effect'). The latter effect increases in time, until the two effects almost cancel out near the end of the 21st century.The analyses were performed for several aggregations of parties in the climate convention (Annex-I/non-Annex-I, 4 IPCC SRES regions, or 17 smaller RIVM IMAGE-regions). We found considerable heterogeneity within aggregated IPCC groups, so that general conclusions drawn for groups as a whole often do not apply to the individual regions within the groups.
The Brazilian proposal for sharing the burden of emissions reductions among Annex-I Parties is based on the relative effect of a country's emissions on the global-mean surface-air temperature. This paper presents calculations of these relative effects, analysing the influence of the time horizon of emissions and of including non-linearities in the global carbon cycle. The analysis shows that an early start date for historical emissions increases the Annex-I contributions to global warming. Choosing an end date of emissions relatively late in time increases non-Annex-I contributions, giving more weight to their larger share in 21st century emissions. Delayed effects of global warming can be taken into account, if contributions are calculated some time after the emission end date. A calculation date long after the emission end date reduces non-Annex-I contributions, mainly because of their relative large share of relatively short-lived methane in total emissions. Our proposal for a new ('non-linear'), transparent approach for attributing CO2 concentrations generally increases non-Annex-I contributions. The impact is larger than that of including non-linearity in radiative forcing ('saturation effect'). The latter effect increases in time, until the two effects almost cancel out near the end of the 21st century.The analyses were performed for several aggregations of parties in the climate convention (Annex-I/non-Annex-I, 4 IPCC SRES regions, or 17 smaller RIVM IMAGE-regions). We found considerable heterogeneity within aggregated IPCC groups, so that general conclusions drawn for groups as a whole often do not apply to the individual regions within the groups.
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