Reto Knutti

Research highlights

The others should do something first…

In a joint report with INFRAS we consider the implications of different burden sharing approaches for different countries in a scenario where greenhouse gases are reduced globally to reach the 2°C target. The interpretation of “common but differentiated responsibility” of course varies in the different burden sharing proposals, but developed countries will have to reduce emissions quickly in all cases.
DownloadEmission pathways to reach 2°C target (PDF, 988 KB)

At least three quarters of warming since 1950 manmade

A new paper in Nature Geoscience demonstrates that the global energy balance provides a strong argument that the observed warming is largely man-made.
DownloadAnthropogenic and natural warming inferred from changes in Earth’s energy balance, Nature Geoscience 2011 (PDF, 470 KB)
external pageNature news: Three-quarters of climate change is man-made
external pageSwissinfo: Bild vom menschlichen Klima-Einfluss komplettiert
external pageScientific American: Three-quarters of climate change is man-made
external pagePhysicsworld: Energy balance points to man-made climate change
external pageDiscovery News: Human factor huge on climate change
external pageBBC: Climate research bolsters 'action' call to UN talks
external pageORF: Der Mensch und der Klimawandel
external pageFAZ: Der kostbare Kaffeesatz in den Klimamodellen
external pageCarbonbrief: At least three-quarters of global temperature rise since the 1950s caused by humans
Klimablog: Neue Studie: Der Fussabdruck des Klimawandels

Is two degrees warming still possible?

A new paper in Nature Climate Change shows emission reductions needed for a 2°C warming target.
DownloadLong-term climate implications of twenty-first century options for carbon dioxide emission mitigation, Nature Climate Change 2011 (PDF, 572 KB)
external pageNature research highlight: Out-of-reach goal to limit warming
external pagePressetext.com: Klimawandel: Zwei-Grad-Ziel "noch erreichbar"
ETH Life: Letzte Chance für verbindliche Treibhausgas-Reduktionen?
Klimablog: Fünf vor zwölf für das 2-Grad-Klimaziel??
Press coverage on the 2°C target before Durban:
DownloadAutorenbeitrag NZZ am Sonntag: Das Klima verdüstert sich (PDF, 338 KB)
DownloadTagblatt: Der Wert der Eisbären (PDF, 3.8 MB)
DownloadSonntagszeitung: Nur mit Verzicht funktioniert das nicht (PDF, 522 KB)
DownloadSonntagszeitung: Die immer gleichen Verlierer (PDF, 1.7 MB)
Additional work from the Climate Physics group:
external pageEmission pathways consistent with a 2 °C global temperature limit, Nature Climate Change 2011
external pageUNEP Report: Bridging the Emissions Gap

Swiss climate change scenarios CH2011

In a new comprehensive report we present new climate change scenarios for Switzerland.
external pageReport, summaries and data. Deutsche Zusammenfassung.
external pageSwiss TV: Tagesschau
external pageDRS Echo der Zeit
external pageSwissinfo: Klimawandel-Szenarien bestätigen Erwärmung
DownloadBund: Klimaschutz greift erst in 40 Jahren (PDF, 156 KB)
ETH Life: CH2011 – die Klimaentwicklung in der Schweiz
Klimablog: Klimabericht «CH2011» – Forschungswissen für die Praxis aufbereitet

Tropics feel the heat

In a new paper we explore potential climate impacts from scenarios with high greenhouse gas emissions that deliberately push the limit of what is plausible.
DownloadThe response of the climate system to very high greenhouse gas emission scenarios, ERL 2011 (PDF, 1.2 MB)
ETH Klimablog: Neue Studie: Worst-Case-Klimaszenarien zeigen starke Klimaerwärmung
ETH Life: Viel wärmer als im schlimmsten Fall?
ETH Life: Much warmer than the worst-case scenario?
external pageEnvironmental Research Web: Going beyond the IPCC ‘worst case’
external pageNZZ: Extreme Annahmen – extremer Klimawandel
external pageTagesanzeiger: Die Natur würde verrückt spielen
DownloadKVMR podcast: Climate models and high emission scenarios (MP3, 2.9 MB)

Which climate model prediction should I trust?

A new study shows that only a small fraction of the fossil fuel reserves can be burnt if a warming of two degrees above preindustrial should be avoided. Peak and equilibrium warming are determined by the total emitted carbon; a tonne of carbon is a tonne of carbon, whether today or in fifty years. Emissions must peak soon and be reduced be at least 50% globally in 2050 to avoid two degree warming.
DownloadNature paper: Greenhouse-gas emission targets for limiting global warming to 2°C (PDF, 2.8 MB)
DownloadCompanion Nature paper: Warming caused by cumulative carbon emissions towards the trillionth tonne (PDF, 838 KB)
DownloadRelated commentary by the authors: The exit strategy (PDF, 329 KB)
DownloadNature News and Views: Too much of a bad thing (PDF, 1.5 MB)
DownloadNature Editorial: Time to act (PDF, 1 MB)
DownloadRelated essay: The worst-case scenario (PDF, 1.1 MB)
DownloadRelated commentary: Overshoot, adapt and recover (PDF, 2.1 MB)
external pageBBC: 'Safe' climate means 'no to coal'
external pageScientific American: How Much Is Too Much?: Estimating Greenhouse Gas Emissions
ETH Life: How the “2°C target” can be reached
external pageNZZ: Was zählt, ist die kumulierte Menge Kohlendioxid
ETH Life: Wie das «2°C-Ziel» erreicht werden kann
external page20 Minuten: Klimawandel erreicht kritischen Wert
external pageSF Tagesschau: Studie mahnt zu dringendem Klimaschutz
external pageSpiegel Online: Kritische Klimagrenze ist nur noch schwer zu erreichen

The 2008 Olympics as an aerosol field experiment

New simulations with the a comprehensive high resolution model under strong mitigation scenarios show that about half of the climate change can be avoided by the end of the century. A two degree warming target preserves much of the permafrost and Arctic sea ice.
DownloadGRL paper: How much climate change can be avoided by mitigation (PDF, 1.5 MB)
DownloadScience editor’s choice: How low can we go? (PDF, 269 KB)
DownloadNature Reports Climate Change Research Highlight: Cuts curb impacts (PDF, 335 KB)
external pageNews New York Times: Emissions Cuts Could Lessen Climate Change
external pageNews 20 Minuten: CO2 muss um 70 Prozent gesenkt werden
external pageNews Focus Online: Die Zukunft der Arktis

Irreversible climate change

Even if carbon emissions were instantly reduced to zero, most of the climate change that has occurred is irreversible for a thousand years. While some impacts are still uncertain, there are robust predictions for both short term impacts like droughts and long term effects like sea level rise.
DownloadPNAS paper: Irreversible climate change due to carbon dioxide emissions (PDF, 982 KB)
external pageRealclimate background article: Irreversible Does Not Mean Unstoppable
external pageNews Swissinfo: Study warns climate change is irreversible
external pageNews New Scientist: Effects of climate change now irreversible
external pageNews Washington Times: Climate change fallout irreversible
external pageNY Times Dot Earth: The Greenhouse Effect and the Bathtub Effect (worth reading!)
ETH Life: Irreversible climate change
ETH Life: Unwiderruflicher Klimawandel
DownloadNews Sonntagszeitung: Tausend Jahre Dürre (PDF, 374 KB)
external pageNews NZZ: Lang anhaltende Folgen der Klimaerwärmung
external pageNews 20 Minuten: Es gibt kein Zurück

Research interests

My research interests are the changes in the global climate system caused by the growing emissions of anthropogenic greenhouse gases like carbon dioxide. I use numerical models of different complexity, from simple energy balance to three-dimensional coupled climate models that resolve the atmosphere, ocean, land, sea ice and their interactions. In particular, I work on simulation of scenarios for future climate change, the quantification of uncertainties in the climate response, and the development of methods to constrain important feedback processes in the climate system by comparing observations with model results.

Reto Knutti

Research highlights

The 2°C climate target and COP in Paris

Humans affect extreme weather

Has global warming stopped?

IPCC AR5, and how to slice the global carbon pie

Ocean eddies influence weather

On the way to four, not two degrees

Climate models: useful or useless?