IPCC Climate Change ReportIPCC Climate Change Report

Moving Towards ConsensusMoving Towards Consensus

Based on real world dataBased on real world data

IPCC Consensus process is IPCC Consensus process is Conservative by NatureConservative by Nature

IPCC Consensus EvolutionIPCC Consensus Evolution

FAR: 1990: The unequivocal FAR: 1990: The unequivocal detection of the enhanced detection of the enhanced greenhouse gas effect from greenhouse gas effect from observations is not likely for a observations is not likely for a decade or moredecade or more

SAR: 1995: The balance of evidence SAR: 1995: The balance of evidence suggestions a discernible human suggestions a discernible human influence on global climateinfluence on global climate

Getting StrongerGetting Stronger

TAR: 2001: There is new and stronger TAR: 2001: There is new and stronger evidence that most of the warming evidence that most of the warming observed over the last 50 years is observed over the last 50 years is attributable to human activitiesattributable to human activities

AT4: 2007: Most of the observed increase AT4: 2007: Most of the observed increase in globally averaged temperatures since in globally averaged temperatures since the mid-20th century is very likely due to the mid-20th century is very likely due to the increase in anthropogenic greenhouse the increase in anthropogenic greenhouse gas concentrations.gas concentrations.

Climate Modeling EvolutionClimate Modeling Evolution

Better Grid ResolutionBetter Grid Resolution

Basic ApproachBasic Approach

Coefficient of doubling COCoefficient of doubling CO22

Preponderance of Preponderance of EvidenceEvidence

Want to find indicators of climate Want to find indicators of climate changechange

Requires a) a robust definition and Requires a) a robust definition and measure of what constitutes climate measure of what constitutes climate and b) an instrumental precision and b) an instrumental precision sufficient to measure changesufficient to measure change

No one indicator (e.g. smoking gun) No one indicator (e.g. smoking gun) exists; aggregate of all data then exists; aggregate of all data then forms the preponderanceforms the preponderance

Hockey Sticks GaloreHockey Sticks Galore

1D Temperature is 1D Temperature is unreliableunreliable

You list the reasons but still …You list the reasons but still …

Reinforced with 2D Reinforced with 2D RepresentationRepresentation

Winter Signal is StrongestWinter Signal is Strongest

More Recent Data – Russian More Recent Data – Russian Heat Wave/FiresHeat Wave/Fires

Extreme Weather ExpectationsExtreme Weather Expectations

And all is superimposed on El Nino Cycle

Convolution of positive and negative forcings are what we observe. GHG produces the net positive here

Global Aerosols – leads to dimming

Mostly Industrial; African Source is pyrogenic and biogenic in nature (drought related)

Other indicators

Sea Ice Glacial retreats and glacial mass balance Permafrost Droughts Water vapor feedback Cloud cover Ocean wave heights Sea surface temperature anamolies

Glacial Retreat and Mass Balance

1941 - 2005

Wholesale Change in Mass Balance

Arctic Ice Loss Rapidly Escalating

But 2009 did not continue this catastrophic trend And 2009 point is consistent with long term

trend

But 2010 mostly did: Significant

Droughts

Sea Level Rising

Sea Level measured at San Francisco

Known SST oscillations increasing in amplitude North Atlantic Oscillation (notice the post

1995 slope):

Complete Feedback Models too Complete Feedback Models too Difficult to reliably constructDifficult to reliably construct

Source of UncertaintiesSource of Uncertainties

Roles of clouds and aerosols in radiative Roles of clouds and aerosols in radiative transfer models? (e.g. scattering!)transfer models? (e.g. scattering!)

Role of tropical convection and the water vapor Role of tropical convection and the water vapor feedback loop?feedback loop?

How well do observations constrain the input How well do observations constrain the input climate parameters?climate parameters?

How to weight the inputs for best fit statistical How to weight the inputs for best fit statistical model?model?

Contributions of other greenhouse gases Contributions of other greenhouse gases specifically methane from permafrost releasespecifically methane from permafrost release

FeedbacksFeedbacks

Ocean Sea Surface Temperature Response Its important to realize that virtually all of the

extra (heat) flux goes into the oceans

Big reservoir of heat

0.1 degree C increase transferred (instantly) to the atmosphere produces 100 degree C increase.

Ocean circulation and redistribution of excess heat is (fortunately) a slow process

But that is where the “pipeline” warming is even if CO2 was stablized today!