wolfgang cramer - f-origin.hypotheses.org · centre a. koyré, paris, november 20, 2014 2001: “in...

Centre A. Koyré, Paris, November 20, 2014

Detection and attribution: Human impact on climate, or climate impact on humans?

Wolfgang Cramer

Institut Méditerranéen de Biodiversité et d'Ecologie (IMBE) Aix-en-Provence, France

Climate change: what exactly do we care about and why? Stockholm (1972): Safeguard the environment

for human well-being Rio de Janeiro (1992): Biodiversity, climate,

desertification Rio de Janeiro (2012): The future we want

– goal-setting

– conventions and protocols - ?

UNFCCC, Article 2

The ultimate objective of this Convention and any related legal instruments that the Conference of the Parties may adopt is to achieve, in accordance with the relevant provisions of the Convention, stabilization of greenhouse gas concentrations in the atmosphere at a level that would prevent dangerous anthropogenic interference with the climate system.

UNFCCC, Article 2

The ultimate objective of this Convention and any related legal instruments that the Conference of the Parties may adopt is to achieve, in accordance with the relevant provisions of the Convention, stabilization of greenhouse gas concentrations in the atmosphere at a level that would prevent dangerous anthropogenic interference with the climate system.

UNFCCC, Article 2

Such a level should be achieved within a time-frame sufficient •  to allow ecosystems to adapt naturally to climate change,

•  to ensure that food production is not threatened and

•  to enable economic development to proceed in a sustainable manner.

UNFCCC, Article 2

If we know where we want to go – how do we find out how far we have gone already?

“…dangerous interference…”

Do human emissions of greenhouse gases interfere with the

atmosphere?

Do human emissions of greenhouse gases interfere with the

atmosphere?

Does climate change have an impact on human well-being?

Dangerous interference may already be visible can be predicted for the foreseeable future

(today’s talk is only about observed changes)

So, has “interference” been proven beyond (reasonable) doubt? Old experimental evidence (Arrhenius) Observed trends correlated with GHG emissions Observed changes in the atmosphere physically explained

In the words of the IPCC (WG1):

2001: “In the light of new evidence and taking into account the remaining uncertainties, most of the observed warming over the last 50 years is likely to have been due to the increase in greenhouse gas concentrations.”

2007: “The widespread change detected in temperature observations of the surface, free atmosphere and ocean, together with consistent evidence of change in other parts of the climate system, strengthens the conclusion that greenhouse gas forcing is the dominant cause of warming during the past several decades.”

2013: “More than half of the observed increase in global mean surface temperature from 1951 to 2010 is very likely due to the observed anthropogenic increase in greenhouse gas concentrations.”

Why so complicated? Following UNFCCC, serious policy changes are inevitable if: •  interference is established •  that interference is dangerous •  policy makers and the public are

convinced

Could you kindly rephrase that in

equivocal, inaccurate, vague, self-serving and roundabout terms that we can all understand?

What about “dangerous”?

UNFCCC, Article 2

For impacts to qualify as “dangerous”, we must show that • some system has changed • that change is due to climate change • the change affects people (or things people value)

Impacts on ice and water •  Water cycle is closely integrated into the

climate system •  Relatively simple to measure and model

•  Detection and attribution are therefore straightforward

Centre A. Koyré, Paris, November 20, 2014 S Rahmstorf, PIK

Centre A. Koyré, Paris, November 20, 2014 Pakistan, August 2010

Impacts on biodiversity and ecosystems •  Organisms are sensitive to weather and

climate •  Climate change has happened before •  Ecosystems are affected by many

forcings •  Detection and attribution are therefore

more complex

Centre A. Koyré, Paris, November 20, 2014 Rosenzweig et al. 2005 (IPCC AR4 WG2)

Centre A. Koyré, Paris, November 20, 2014 NOAA Pacific Islands Fisheries Science Center

Locations of observed biome shifts during the 20th century, derived from Gonzalez et al. (2010) Settele et al. 2014 (IPCC AR5 WG2)

Centre A. Koyré, Paris, November 20, 2014 Lorraine, France, August 2003

Settele et al. in press (IPCC AR5 WG2)

Impacts on human systems •  Human society is in quick development •  Human environment in under multiple

forcings of degradation •  Detection and attribution are therefore

highly complex •  Absence of detected impacts does not

imply absence of impacts

Wheat yields in France

(Brisson et al. 2010)

Hurricane Sandy, Oct 2012 http://en.wikipedia.org/wiki/Hurricane_Sandy

Rosenzweig et al. 2005 (IPCC AR4 WG2)

Cramer et al. 2014 (IPCC AR5 WG2)

Again, in the words of the IPCC (WG2):

2001: “Available observational evidence indicates that regional changes in climate, particularly increases in temperature, have already affected a diverse set of physical and biological systems in many parts of the world..”

2007: “Observational evidence from all continents and most oceans shows that many natural systems are being affected by regional climate changes, particularly temperature increases.”

2014: “In recent decades, changes in climate have caused impacts on natural and human systems on all continents and across the oceans. Evidence of climate-change impacts is strongest and most comprehensive for natural systems. Some impacts on human systems have also been attributed to climate change.”

2001: “Available observational evidence indicates that regional changes in climate, particularly increases in temperature, have already affected a diverse set of physical and biological systems in many parts of the world..”

2007: “Observational evidence from all continents and most oceans shows that many natural systems are being affected by regional climate changes, particularly temperature increases.”

2014: “In recent decades, changes in climate have caused impacts on natural and human systems on all continents and across the oceans. Evidence of climate-change impacts is strongest and most comprehensive for natural systems. Some impacts on human systems have also been attributed to climate change.”

Could you kindly rephrase that in

equivocal, inaccurate, vague, self-serving and roundabout terms that we can all understand?

You did not show OUR impacts!

Cramer et al. 2014 (IPCC AR5 WG2)

Rockström et al. 2009

Global fresh- water use

Transgressing safe boundaries

In conclusion: • Detection and attribution of human interference with the climate system is “done” • Detection and attribution of “dangerous” impacts is more complex: o  Causality chains are longer o  Confounding forcings are stronger o  Stakeholder interests differ

Can we conclude that there is less confidence in impact attribution to climate change than there is in attribution of human interference?

To you all to decide…

Thank you very much for your a0en1on!

wolfgang cramer - f-origin.hypotheses.org · centre a. koyré, paris, november 20, 2014 2001: “in...

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