This is where the understanding
of climate modeling uncertainty is lost in the scientific communications to the public by the politicians and vocal advocates that drive climate change discussions.
Tim Palmer's presentation was superb and very relevant to our discussions
of climate model uncertainty.
More complete exploration
of climate model uncertainty, including unknowns and model structural uncertainty
Not exact matches
Reducing
uncertainties in the
models could lead to better long - term assessments
of climate, Esposito says.
Some
of the largest
uncertainties in current
climate models stem from their wide - ranging estimates
of the size and number
of dust particles in the atmosphere.
Modeling future
climate scenarios is a notoriously tricky science, involving wide margins
of uncertainty, myriad variables and a profusion
of data.
By improving the understanding
of how much radiation CO2 absorbs,
uncertainties in
modelling climate change will be reduced and more accurate predictions can be made about how much Earth is likely to warm over the next few decades.
Therefore, Caldeira said, the more important question - and one
of the largest sources
of uncertainty in
climate models - is «will the end
of oil usher in a century
of coal, or will it usher in a transition toward low - carbon - emitting technologies?»
Three approaches were used to evaluate the outstanding «carbon budget» (the total amount
of CO2 emissions compatible with a given global average warming) for 1.5 °C: re-assessing the evidence provided by complex Earth System
Models, new experiments with an intermediate - complexity
model, and evaluating the implications
of current ranges
of uncertainty in
climate system properties using a simple
model.
Mission leaders were relieved and eager to begin their studies
of cloud and haze effects, which «constitute the largest
uncertainties in our
models of future
climate — that's no exaggeration,» says Jens Redemann, an atmospheric scientist at NASA's Ames Research Center in Mountain View, California, and the principal investigator for ObseRvations
of Aerosols above CLouds and their IntEractionS (ORACLES).
Any detailed, careful reading
of the
climate models includes a great deal
of uncertainty.
The
uncertainty associated with future
climate projections linked to economic possibilities
of what people will do is far larger than the
uncertainty associated with physical
climate models.
Using a hierarchical
model, the authors combine information from these various sources to obtain an ensemble estimate
of current and future
climate along with an associated measure
of uncertainty.
Clouds also are the largest source
of uncertainty in present
climate models, according to the latest report of the Intergovernmental Panel on Climate
climate models, according to the latest report
of the Intergovernmental Panel on
Climate Climate Change.
A recent study in the Journal
of Environmental Management carried out by researchers at the European Forest Institute and their partners in the FP7 funded MOTIVE project (
Models for Adaptive Forest Management) discusses how forest managers and decision makers can cope with
climate uncertainties.
«A cloud system - resolved
model can reduce one
of the greatest
uncertainties in
climate models, by improving the way we treat clouds,» Wehner said.
For example, when examining hurricanes and typhoons, the lack
of a high - quality, long - term historical record,
uncertainty regarding the impact
of climate change on storm frequency and inability to accurately simulate these storms in most global
climate models raises significant challenges when attributing assessing the impact
of climate change on any single storm.
But calculating the fraction
of warming is a far more contentious task, points out climatologist Stephen H. Schneider
of Stanford University, because
of the inherent
uncertainty and variability
of climate models.
However, he says, «Aerosol effects on
climate are one
of the main
uncertainties in
climate models.
Gary Geernaert, director
of DOE's
Climate and Environmental Sciences Division, states that «it is critical that federal investments to advance climate science for use by both public and private stakeholders must place significant priority on incorporating uncertainty quantification methodologies into modeling fram
Climate and Environmental Sciences Division, states that «it is critical that federal investments to advance
climate science for use by both public and private stakeholders must place significant priority on incorporating uncertainty quantification methodologies into modeling fram
climate science for use by both public and private stakeholders must place significant priority on incorporating
uncertainty quantification methodologies into
modeling frameworks.
By 2100, the choice
of driving
climate model conditions dominates the
uncertainty, but by 2200, the
uncertainty in the ice sheet
model and the elevation scheme are larger.
That
uncertainty is represented in the latest crop
of global
climate models, which assume a
climate sensitivity
of anywhere from about 3 to 8 degrees F.
Those data, to be collected this year and next, could improve
climate models, which account poorly for these atmospheric interactions and contain «horrific»
uncertainties about the levels and behaviour
of water vapour at stratospheric altitudes, Austin says.
«The
model we developed and applied couples biospheric feedbacks from oceans, atmosphere, and land with human activities, such as fossil fuel emissions, agriculture, and land use, which eliminates important sources
of uncertainty from projected
climate outcomes,» said Thornton, leader of the Terrestrial Systems Modeling group in ORNL's Environmental Sciences Division and deputy director of ORNL's Climate Change Science Ins
climate outcomes,» said Thornton, leader
of the Terrestrial Systems
Modeling group in ORNL's Environmental Sciences Division and deputy director
of ORNL's
Climate Change Science Ins
Climate Change Science Institute.
As can be seen your graph, our
climate models make a wide range
of predictions (perhaps 0.5 - 5 degC, a 10-fold
uncertainty) about how much «committed warming» will occur in the future under any stabilization scenario, so we don't seem to have a decent understanding
of these processes.
Oppenheimer and his co-authors use a technique known as «structured expert judgment» to put an actual value on the
uncertainty that scientists studying
climate change have about a particular
model's prediction
of future events such as sea - level rise.
By providing new data on how CO2 cycles through land and ocean plants, HIPPO will allow researchers to improve the accuracy
of their
climate models and reduce that
uncertainty, Stephens said.
PNNL researchers play a key role in reducing
uncertainty through improved process understanding and
modeling of climate processes such as clouds and aerosols.
Click here for Part II, an accounting
of Exxon's early
climate research; Part III, a review
of Exxon's
climate modeling efforts; Part IV, a dive into Exxon's Natuna gas field project; Part V, a look at Exxon's push for synfuels; Part VI, an accounting
of Exxon's emphasis on
climate science
uncertainty.
After the field campaign, Fast will perform computer simulations to help evaluate all
of the field campaign data and quantify the
uncertainties associated with using coarse grid global
climate models to study megacity emissions and to determine the radiative impact
of the Mexico City particulates on the local and regional
climate.
Understanding how well
climate models represent these processes will help reduce
uncertainties in the
model projections
of the effects
of global warming on the world's water cycle.
One
of the largest
uncertainties in global
climate models (GCMs) is the response
of clouds in a warming world.
«Current global
climate models have failed to predict the rapid Arctic warming, and clouds are one
of the largest
uncertainties.
Stakeholders
of Montana agriculture may find the cumulative
uncertainty of inexact crop
models built on inexact
climate models frustrating, but it is as important to understand the sources
of uncertainty as it is to realize that temperatures are rising.
Uncertainty quantification is also a focus for the U.S. Department
of Energy (DOE) as eight national laboratories and six partner institutions collaborate to develop and apply the next generation
of climate and Earth - system
models to the challenges and demands
of climate - change research.
Much
of the
uncertainty in projections
of global
climate change is due to the complexity
of clouds, aerosols, and cloud - aerosol interactions, and the difficulty
of incorporating this information into
climate models.
Dufresne, 2005: Marine boundary - layer clouds at the heart
of tropical cloud feedback
uncertainties in
climate models.
Therefore, I wouldn't attach much credence, if any, to a
modelling study that didn't explore the range
of possibilities arising from such
uncertainty in parameter values, and particularly in the value
of something as crucial as the
climate sensitivity parameter, as in this example.
There is still
uncertainty about many aspects
of the dynamics
of climate change, and this will only be addressed by investment in
climate models and the top -
of - the - range supercomputers needed to run them.
Murphy, J.M., et al., 2004: Quantification
of modelling uncertainties in a large ensemble
of climate change simulations.
They got 10 pages in Science, which is a lot, but in it they cover radiation balance, 1D and 3D
modelling,
climate sensitivity, the main feedbacks (water vapour, lapse rate, clouds, ice - and vegetation albedo); solar and volcanic forcing; the
uncertainties of aerosol forcings; and ocean heat uptake.
Due to the complexity
of physical processes,
climate models have
uncertainties in global temperature prediction.
Given that clouds are known to be the primary source
of uncertainty in
climate sensitivity, how much confidence can you place in a study based on a
model that doesn't even attempt to simulate clouds?
However, in view
of the fact that cloud feedbacks are the dominant contribution to
uncertainty in
climate sensitivity, the fact that the energy balance
model used by Schmittner et al can not compute changes in cloud radiative forcing is particularly serious.
«The inertia in the
climate system makes it possible to predict, within
model uncertainty, changes in flood hazards up to the year 2040, independent
of the specific carbon emission pathway that is chosen by society within the next 25 years.»
Wigley et al. (1997) pointed out that
uncertainties in forcing and response made it impossible to use observed global temperature changes to constrain ECS more tightly than the range explored by
climate models at the time (1.5 °C to 4.5 °C), and particularly the upper end
of the range, a conclusion confirmed by subsequent studies.
Reduction
of these
uncertainties will be crucial for evaluating and better constraining
climate models.
It is not all that earthshaking that the numbers in Schmittner et al come in a little low: the 2.3 ºC is well within previously accepted
uncertainty, and three
of the IPCC AR4
models used for future projections have a
climate sensitivity
of 2.3 ºC or lower, so that the range
of IPCC projections already encompasses this possibility.
M2009 use a simplified carbon cycle and
climate model to make a large ensemble
of simulations in which principal
uncertainties in the carbon cycle, radiative forcings, and
climate response are allowed to vary, thus yielding a probability distribution for global warming as a function
of time throughout the 21st century.
«We use a massive ensemble
of the Bern2.5 D
climate model of intermediate complexity, driven by bottom - up estimates
of historic radiative forcing F, and constrained by a set
of observations
of the surface warming T since 1850 and heat uptake Q since the 1950s... Between 1850 and 2010, the
climate system accumulated a total net forcing energy
of 140 x 1022 J with a 5 - 95 %
uncertainty range
of 95 - 197 x 1022 J, corresponding to an average net radiative forcing
of roughly 0.54 (0.36 - 0.76) Wm - 2.»