IPCC Climate Change ReportIPCC Climate Change ReportMoving 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

Leads to COLeads to CO22 Stabilization Stabilization ScenariosScenarios

Basic Future PredictionsBasic Future Predictions A 2°C rise from today's temperatures A 2°C rise from today's temperatures

produces 30% species extinctionproduces 30% species extinction A 3°C warming will lead to widespread A 3°C warming will lead to widespread

coral deathscoral deaths Water availability in the moist tropics and Water availability in the moist tropics and

in the high latitudes will increase, but will in the high latitudes will increase, but will drop in the semi-arid low latitudesdrop in the semi-arid low latitudes

A 1°C warming will decrease agricultural A 1°C warming will decrease agricultural yields in the low-latitudes; 2°C increases yields in the low-latitudes; 2°C increases yields at high latitudesyields at high latitudes

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

Reinforced with 2D Reinforced with 2D RepresentationRepresentation

Winter Signal is StrongestWinter Signal is Strongest

Central Europe Summer Central Europe Summer SignalSignal

Huge statistical signal via Huge statistical signal via baseline/area testbaseline/area test

Record Events depend on wave Record Events depend on wave form evolutionform evolution

Global Aerosols – leads to dimming

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

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

And all is superimposed on El Nino Cycle

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

Droughts

Water vapor increases?

Cloud Cover

Extremely difficult to really measure with any accuracy

Extant data are inconclusive and noisy

Wave height data shows something!

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!

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

Global Warming Potential

TH = Time Horizon (20 or 100 years) Ax = increased forcing from X (Watts m^2 kg) x(t) = decay following some hypothetical

instantaneous release of X Denominator is relevant quantities for CO2 Nominal value for Methane is 21

Do Tipping Points Exist in Climate? Does the system have critical phenomena?

Or do the various and somewhat unknown feedback mechanisms serve to counter this?

The Next Level of Physics in Climate Science More strongly incorporates the role of various

feedbacks particularly water vapor Identifying critical points (or lack thereof) is

essential in future models Improved modeling of aerosols and their

scattering properties Improved modeling of tropical convection to

better understand ocean/atmosphere heat exchange