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!