Which global warming ? A geophysicists politically incorrect look at climate change. Vincent Courtillot University Paris-Diderot and Institut de Physique.

Which global warming ? A geophysicist’s politically incorrect look at climate change.

Vincent CourtillotUniversity Paris-Diderot and Institut de Physique du Globe de Paris

Conference on Climate and Energy, Berlin Manhattan Institute, December 3rd, 2010

Sorbonne Paris Cité

Observations (1):Observations (1):

a critical look ata critical look atglobal and some regional temperature data…global and some regional temperature data…

Global mean temperature changes are small and not easy to determine with confidence

IPCC WG1 Fourth Assessment Report, 2007

Global temperature anomalies1906-2005

Continentalmeans

(decadal)

blue = natural forcings

pink = with anthropic forcings

Mean daily minimum temperature (°C)for 44 European meteorological stations

(3yr running means)

Mean daily minimum temperature (°C)for 150 US meteorological stations

(3yr running means)

Comparison between IPCC curves and our recalculated curves for Europe and the US

IPCC WG1 Fourth Assessment Report, 2007

Le Mouël et al, 2008, 2009

An icon of global warming :Mann’s hockey stick curve

1000 2000

Mann

Moberg

Tree ring width (TRW) and density (MXD) :

a function of cambial age,hence a serious artefact

Grudd, 2008

Recent global warming is often labeled as« abnormal » or « without precedent ».

It actually had equivalents in 750, 1000, 1400 and 1750 andthe two-century long period around 1000AD

was warmer and longer than generally recognized…at least in Northern Europe

Medieval climatic optimum

Grudd, 2008

Grudd, 2008

Grudd, 2002

Observations (2):Observations (2):

our group’s work in the past 5 years…our group’s work in the past 5 years…

Decadal and longer-term (multi-decadal)changes in solar activity

A summary of recent results

Decadal and longer-term (multi-decadal)changes in solar activity

A summary of recent results

Correlation between solar activity and mean inter-annual quadratic variation (or lifetime) of temperature

for Europe (left) and Holland (right).

Le Mouël et al, 2009

1

Time variations of the mean period of the MJO

wave packet (MJO1 index), taken between

30–60 days (a) and 50–80 days (b).

The difference between the two is compared to sunspot

number (c) and mean quadratic variation of Z component in the Alibag

magnetic observatory (d).

(4 year running means)

The Madden-Julian

oscillation

2

Evidence ofEvidence of11-yr cycle related 11-yr cycle related modulation of themodulation of the

6 month spectral peak 6 month spectral peak in length-of-dayin length-of-day(Earth rotation)(Earth rotation)

amplitude amplitude

phasephase

Le Mouël et al, GRL, 2010b

3

Comparison toComparison tosunspot numbersunspot number

(reversed in sign and (reversed in sign and with one-year phase with one-year phase

lag)lag)

and to cosmic ray count and to cosmic ray count (no sign or phase (no sign or phase

change)change)

Le Mouël et al, GRL, 2010b

3

Which forcing factors ?Which forcing factors ?

Natural distribution of heat fluxesNatural distribution of heat fluxesin the atmospherein the atmosphere

Clouds reflect about 80 Wm-2

(out of incoming 342 Wm-2)

A 10% change in cloud coverin the 20th century

would have led to a forcing of 8 Wm-2

Correlation between cosmic rays andlow cloud cover

Svensmark, 2007Svensmark, 2007Svensmark, 2007

Highaltitude

Middlealtitude

Lowaltitude

Tinsley et Heelis, 1993

Accumulation of electric charges at the boundaries of layered clouds Accumulation of electric charges at the boundaries of layered clouds results from vertical current density Jzresults from vertical current density Jz

from the ionosphere to the surface.from the ionosphere to the surface.

Charges attach to droplets and aerosols and alter cloud microphysics.Charges attach to droplets and aerosols and alter cloud microphysics.

The « golden triangle » :The « golden triangle » : - observation - observation

- physical mechanisms (« theory ») - physical mechanisms (« theory ») - numerical modeling - numerical modeling

A need for a falsifiable modelA need for a falsifiable model(«  checkable predictions  »)(«  checkable predictions  »)

The importance of uncertainties The importance of uncertainties

Conclusion (1):

Global warming ?Global warming ?

Yes, over the past 150 years,Yes, over the past 150 years,but very irregular…but very irregular…

Not without precedentNot without precedentin the past two thousand years …in the past two thousand years …

Complex and multiple sources,Complex and multiple sources,uncertainties insufficiently taken into accountuncertainties insufficiently taken into account

in models…in models…

Conclusion (2):

Conclusion (3):

Growing evidence along several lines for significant influence of decadal to multi-decadal variations in

solar activity on a number of climate related features, with an amplitude well beyond that expected for

1/1000 changes in total solar irradiance.

Some of the effects we find have a relative amplitude in excess of 30% of the original signals.

Mechanism likely involve cosmic rays and/or vertical currents in ionosphere and atmosphere, and clouds.

How expertise is gathered and advice builtHow expertise is gathered and advice built (the « consensus »): (the « consensus »):

a risk for « anti-science » backfiringa risk for « anti-science » backfiring

Other important problems running the riskOther important problems running the riskof being considered as secundary :of being considered as secundary :

- the quest for drinking water- the quest for drinking water- management of urban waste- management of urban waste

- hunger in the world …- hunger in the world …

Geoscientists can be sources of solutionsGeoscientists can be sources of solutionsto several of these problems…to several of these problems…

Conclusion (4) and discussion: