TY  - JOUR
A1  - Kikstra, Jarmo S.
A1  - Nicholls, Zebedee R. J.
A1  - Smith, Christopher J.
A1  - Lewis, Jared
A1  - Lamboll, Robin D.
A1  - Byers, Edward
A1  - Sandstad, Marit
A1  - Meinshausen, Malte
A1  - Gidden, Matthew J.
A1  - Rogelj, Joeri
A1  - Kriegler, Elmar
A1  - Peters, Glen P.
A1  - Fuglestvedt, Jan S.
A1  - Skeie, Ragnhild B.
A1  - Samset, Bjørn H.
A1  - Wienpahl, Laura
A1  - van Vuuren, Detlef P.
A1  - van der Wijst, Kaj-Ivar
A1  - Al Khourdajie, Alaa
A1  - Forster, Piers M.
A1  - Reisinger, Andy
A1  - Schaeffer, Roberto
A1  - Riahi, Keywan
T1  - The IPCC Sixth Assessment Report WGIII climate assessment of mitigation pathways
BT  - from emissions to global temperatures
JF  - Geoscientific model development
N2  - While the Intergovernmental Panel on Climate Change (IPCC) physical science reports usually assess a handful of future scenarios, the Working Group III contribution on climate mitigation to the IPCC's Sixth Assessment Report (AR6 WGIII) assesses hundreds to thousands of future emissions scenarios. A key task in WGIII is to assess the global mean temperature outcomes of these scenarios in a consistent manner, given the challenge that the emissions scenarios from different integrated assessment models (IAMs) come with different sectoral and gas-to-gas coverage and cannot all be assessed consistently by complex Earth system models. In this work, we describe the “climate-assessment” workflow and its methods, including infilling of missing emissions and emissions harmonisation as applied to 1202 mitigation scenarios in AR6 WGIII. We evaluate the global mean temperature projections and effective radiative forcing (ERF) characteristics of climate emulators FaIRv1.6.2 and MAGICCv7.5.3 and use the CICERO simple climate model (CICERO-SCM) for sensitivity analysis. We discuss the implied overshoot severity of the mitigation pathways using overshoot degree years and look at emissions and temperature characteristics of scenarios compatible with one possible interpretation of the Paris Agreement. We find that the lowest class of emissions scenarios that limit global warming to “1.5 ∘C (with a probability of greater than 50 %) with no or limited overshoot” includes 97 scenarios for MAGICCv7.5.3 and 203 for FaIRv1.6.2. For the MAGICCv7.5.3 results, “limited overshoot” typically implies exceedance of median temperature projections of up to about 0.1 ∘C for up to a few decades before returning to below 1.5 ∘C by or before the year 2100. For more than half of the scenarios in this category that comply with three criteria for being “Paris-compatible”, including net-zero or net-negative greenhouse gas (GHG) emissions, median temperatures decline by about 0.3–0.4 ∘C after peaking at 1.5–1.6 ∘C in 2035–2055. We compare the methods applied in AR6 with the methods used for SR1.5 and discuss their implications. This article also introduces a “climate-assessment” Python package which allows for fully reproducing the IPCC AR6 WGIII temperature assessment. This work provides a community tool for assessing the temperature outcomes of emissions pathways and provides a basis for further work such as extending the workflow to include downscaling of climate characteristics to a regional level and calculating impacts.
Y1  - 2022
U6  - https://doi.org/10.5194/gmd-15-9075-2022
SN  - 1991-959X
SN  - 1991-9603
VL  - 15
IS  - 24
SP  - 9075
EP  - 9109
PB  - Copernicus
CY  - Katlenburg-Lindau
ER  - 
TY  - JOUR
A1  - Schleussner, Carl-Friedrich
A1  - Rogelj, Joeri
A1  - Schaeffer, Michiel
A1  - Lissner, Tabea
A1  - Licker, Rachel
A1  - Fischer, Erich M.
A1  - Knutti, Reto
A1  - Levermann, Anders
A1  - Frieler, Katja
A1  - Hare, William
T1  - Science and policy characteristics of the Paris Agreement temperature goal
JF  - Nature climate change
Y1  - 2016
U6  - https://doi.org/10.1038/NCLIMATE3096
SN  - 1758-678X
SN  - 1758-6798
VL  - 6
SP  - 827
EP  - 835
PB  - Nature Publ. Group
CY  - London
ER  - 
TY  - JOUR
A1  - Schultes, Anselm
A1  - Piontek, Franziska
A1  - Soergel, Bjoern
A1  - Rogelj, Joeri
A1  - Baumstark, Lavinia
A1  - Kriegler, Elmar
A1  - Edenhofer, Ottmar
A1  - Luderer, Gunnar
T1  - Economic damages from on-going climate change imply deeper near-term emission cuts
JF  - Environmental research letters
N2  - Pathways toward limiting global warming to well below 2 ∘C, as used by the IPCC in the Fifth Assessment Report, do not consider the climate impacts already occurring below 2 ∘C. Here we show that accounting for such damages significantly increases the near-term ambition of transformation pathways. We use econometric estimates of climate damages on GDP growth and explicitly model the uncertainty in the persistence time of damages. The Integrated Assessment Model we use includes the climate system and mitigation technology detail required to derive near-term policies. We find an optimal carbon price of $115 per tonne of CO2 in 2030. The long-term persistence of damages, while highly uncertain, is a main driver of the near-term carbon price. Accounting for damages on economic growth increases the gap between the currently pledged nationally determined contributions and the welfare-optimal 2030 emissions by two thirds, compared to pathways considering the 2 ∘C limit only.
KW  - climate change
KW  - climate mitigation
KW  - climate impacts
KW  - integrated assessment
Y1  - 2021
U6  - https://doi.org/10.1088/1748-9326/ac27ce
SN  - 1748-9326
VL  - 16
IS  - 10
PB  - IOP Publishing
CY  - Bristol
ER  - 
TY  - JOUR
A1  - Schleussner, Carl-Friedrich
A1  - Lissner, Tabea K.
A1  - Fischer, Erich M.
A1  - Wohland, Jan
A1  - Perrette, Mahe
A1  - Golly, Antonius
A1  - Rogelj, Joeri
A1  - Childers, Katelin
A1  - Schewe, Jacob
A1  - Frieler, Katja
A1  - Mengel, Matthias
A1  - Hare, William
A1  - Schaeffer, Michiel
T1  - Differential climate impacts for policy-relevant limits to global warming: the case of 1.5 degrees C and 2 degrees C
JF  - Earth system dynamics
N2  - Robust appraisals of climate impacts at different levels of global-mean temperature increase are vital to guide assessments of dangerous anthropogenic interference with the climate system. The 2015 Paris Agreement includes a two-headed temperature goal: "holding the increase in the global average temperature to well below 2 degrees C above pre-industrial levels and pursuing efforts to limit the temperature increase to 1.5 degrees C". Despite the prominence of these two temperature limits, a comprehensive overview of the differences in climate impacts at these levels is still missing. Here we provide an assessment of key impacts of climate change at warming levels of 1.5 degrees C and 2 degrees C, including extreme weather events, water availability, agricultural yields, sea-level rise and risk of coral reef loss. Our results reveal substantial differences in impacts between a 1.5 degrees C and 2 degrees C warming that are highly relevant for the assessment of dangerous anthropogenic interference with the climate system. For heat-related extremes, the additional 0.5 degrees C increase in global-mean temperature marks the difference between events at the upper limit of present-day natural variability and a new climate regime, particularly in tropical regions. Similarly, this warming difference is likely to be decisive for the future of tropical coral reefs. In a scenario with an end-of-century warming of 2 degrees C, virtually all tropical coral reefs are projected to be at risk of severe degradation due to temperature-induced bleaching from 2050 onwards. This fraction is reduced to about 90% in 2050 and projected to decline to 70% by 2100 for a 1.5 degrees C scenario. Analyses of precipitation-related impacts reveal distinct regional differences and hot-spots of change emerge. Regional reduction in median water availability for the Mediterranean is found to nearly double from 9% to 17% between 1.5 degrees C and 2 degrees C, and the projected lengthening of regional dry spells increases from 7 to 11%. Projections for agricultural yields differ between crop types as well as world regions. While some (in particular high-latitude) regions may benefit, tropical regions like West Africa, South-East Asia, as well as Central and northern South America are projected to face substantial local yield reductions, particularly for wheat and maize. Best estimate sea-level rise projections based on two illustrative scenarios indicate a 50cm rise by 2100 relative to year 2000-levels for a 2 degrees C scenario, and about 10 cm lower levels for a 1.5 degrees C scenario. In a 1.5 degrees C scenario, the rate of sea-level rise in 2100 would be reduced by about 30% compared to a 2 degrees C scenario. Our findings highlight the importance of regional differentiation to assess both future climate risks and different vulnerabilities to incremental increases in global-mean temperature. The article provides a consistent and comprehensive assessment of existing projections and a good basis for future work on refining our understanding of the difference between impacts at 1.5 degrees C and 2 degrees C warming.
Y1  - 2016
U6  - https://doi.org/10.5194/esd-7-327-2016
SN  - 2190-4979
SN  - 2190-4987
VL  - 7
SP  - 327
EP  - 351
PB  - Copernicus
CY  - Göttingen
ER  - 
TY  - JOUR
A1  - Riahi, Keywan
A1  - Bertram, Christoph
A1  - Huppmann, Daniel
A1  - Rogelj, Joeri
A1  - Bosetti, Valentina
A1  - Cabardos, Anique-Marie
A1  - Deppermann, Andre
A1  - Drouet, Laurent
A1  - Frank, Stefan
A1  - Fricko, Oliver
A1  - Fujimori, Shinichiro
A1  - Harmsen, Mathijs
A1  - Hasegawa, Tomoko
A1  - Krey, Volker
A1  - Luderer, Gunnar
A1  - Paroussos, Leonidas
A1  - Schaeffer, Roberto
A1  - Weitzel, Matthias
A1  - van der Zwaan, Bob
A1  - Vrontisi, Zoi
A1  - Longa, Francesco Dalla
A1  - Després, Jacques
A1  - Fosse, Florian
A1  - Fragkiadakis, Kostas
A1  - Gusti, Mykola
A1  - Humpenöder, Florian
A1  - Keramidas, Kimon
A1  - Kishimoto, Paul
A1  - Kriegler, Elmar
A1  - Meinshausen, Malte
A1  - Nogueira, Larissa Pupo
A1  - Oshiro, Ken
A1  - Popp, Alexander
A1  - Rochedo, Pedro R. R.
A1  - Ünlü, Gamze
A1  - van Ruijven, Bas
A1  - Takakura, Junya
A1  - Tavoni, Massimo
A1  - van Vuuren, Detlef P.
A1  - Zakeri, Behnam
T1  - Cost and attainability of meeting stringent climate targets without overshoot
JF  - Nature climate change
N2  - Global emissions scenarios play a critical role in the assessment of strategies to mitigate climate change. The current scenarios, however, are criticized because they feature strategies with pronounced overshoot of the global temperature goal, requiring a long-term repair phase to draw temperatures down again through net-negative emissions. Some impacts might not be reversible. Hence, we explore a new set of net-zero CO2 emissions scenarios with limited overshoot. We show that upfront investments are needed in the near term for limiting temperature overshoot but that these would bring long-term economic gains. Our study further identifies alternative configurations of net-zero CO2 emissions systems and the roles of different sectors and regions for balancing sources and sinks. Even without net-negative emissions, CO2 removal is important for accelerating near-term reductions and for providing an anthropogenic sink that can offset the residual emissions in sectors that are hard to abate.
Y1  - 2021
U6  - https://doi.org/10.1038/s41558-021-01215-2
SN  - 1758-678X
SN  - 1758-6798
VL  - 11
IS  - 12
SP  - 1063
EP  - 1069
PB  - Nature Publishing Group
CY  - London
ER  -