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