IPCC Climate Change Report Moving Towards Consensus Based on real world data

IPCC Consensus process is Conservative by Nature

IPCC Consensus Evolution FAR: 1990: The unequivocal detection of the enhanced greenhouse gas effect from observations is not likely for a decade or more FAR: 1990: The unequivocal detection of the enhanced greenhouse gas effect from observations is not likely for a decade or more SAR: 1995: The balance of evidence suggestions a discernible human influence on global climate SAR: 1995: The balance of evidence suggestions a discernible human influence on global climate

Getting Stronger TAR: 2001: There is new and stronger evidence that most of the warming observed over the last 50 years is attributable to human activities TAR: 2001: There is new and stronger evidence that most of the warming observed over the last 50 years is attributable to human activities AT4: 2007: Most of the observed increase in globally averaged temperatures since the mid-20th century is very likely due to the increase in anthropogenic greenhouse gas concentrations. AT4: 2007: Most of the observed increase in globally averaged temperatures since the mid-20th century is very likely due to the increase in anthropogenic greenhouse gas concentrations.

Climate Modeling Evolution

Better Grid Resolution

Basic Approach Coefficient of doubling CO 2 Coefficient of doubling CO 2

Leads to CO 2 Stabilization Scenarios

Basic Future Predictions A 2°C rise from today's temperatures produces 30% species extinction A 2°C rise from today's temperatures produces 30% species extinction A 3°C warming will lead to widespread coral deaths A 3°C warming will lead to widespread coral deaths Water availability in the moist tropics and in the high latitudes will increase, but will drop in the semi-arid low latitudes Water availability in the moist tropics and in the high latitudes will increase, but will drop in the semi-arid low latitudes A 1°C warming will decrease agricultural yields in the low-latitudes; 2°C increases yields at high latitudes A 1°C warming will decrease agricultural yields in the low-latitudes; 2°C increases yields at high latitudes

Equilibrium Temperature  Planet radiates as a blackbody in TE with incoming solar radiation: A = Albedo; L = 1370 watts per sq meter T = 278(1-A) 4 T = 255K for A=0.32 This is not the right answer compared to observations

The Role of the Atmosphere F o = incident flux T s = transmission % incoming T t = transmission % outgoing F g = Flux from ground F a = Flux from the atmosphere. F o = F a + T t F g top of atmosphere equilibrium F g = F a + T s F o outgoing ground equilibrium Let F a = F o –T t F g F g = F o

An Inconvenient Coincidence

Preponderance of Evidence Want to find indicators of climate change Want to find indicators of climate change Requires a) a robust definition and measure of what constitutes climate and b) an instrumental precision sufficient to measure change Requires a) a robust definition and measure of what constitutes climate and b) an instrumental precision sufficient to measure change No one indicator (e.g. smoking gun) exists; aggregate of all data then forms the preponderance No one indicator (e.g. smoking gun) exists; aggregate of all data then forms the preponderance

Global mean temperature Contamination and data reliability/correction problems render this approach the least convincing Contamination and data reliability/correction problems render this approach the least convincing This is reflected in the relatively large error bars on overall amplitude of warming This is reflected in the relatively large error bars on overall amplitude of warming

Consensus in Data Sets But different analyses use different sets of thermometers and different selection criteria But different analyses use different sets of thermometers and different selection criteria Statistical agreement is good Statistical agreement is good

Recent Trends Compared to earlier assessments Shows the effect of including more of the physics Shows the effect of including more of the physics

Expected higher latitude signal clearly seen

Reinforced with 2D Representation

Winter Signal is Strongest

Both a Surface and Tropospheric (1-3 km) effect

Central Europe Summer Signal Huge statistical signal via baseline/area test Huge statistical signal via baseline/area test

Record Events depend on wave form evolution

Global Dimming? A potential competeting affect that has masked the true signal Results mostly from global aerosal injection and increase of short wave length scattering surfaces Convolution of rayleigh/mie scattering mix is poorly understood Volcanic eruptions are also important

Volcanic Eruptions

Global Aresols 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

Putting it altogether

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

Sea Ice – opening of the NW Passage

Glacial Retreat and Mass Balance

Wholesale Change in Mass Balance

Permafrost indicators

Summary of the Cyrosphere (frozen land) observations

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 CO 2 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):

Future predictions remain uncertain

Physics of Atmospheric Energy Transport is difficult Potential energy Internal energy Kinetic energy Latent heat Latitude dependent; vertical dependence

Complete Feedback Models too Difficult to reliably construct

Source of Uncertainties  Roles of clouds and aerosols in radiative transfer models? (e.g. scattering!)  Role of tropical convection and the water vapor feedback loop?  How well do observations constrain the input climate parameters?  How to weight the inputs for best fit statistical model?  Contributions of other greenhouse gases specifically methane from permafrost release

Global Warming Potential TH = Time Horizon (20 or 100 years) A x = increased forcing from X (Watts m^2 kg) x(t) = decay following some hypothetical instantaneous release of X Denominator is relevant quantities for CO 2 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