Not exact matches
Furthermore, all approaches that use the climate's time evolution attempt to account for
uncertainty due to internal climate variability, either by bootstrapping (Andronova and Schlesinger, 2001), by using a
noise model in fingerprint studies whose results are used (Frame et al., 2005) or directly (Forest et al., 2002, 2006).
First, doesn't the
model uncertainty include both
model noise (i.e., weather fluctuations) and systematic differences among the
models?
The question about
uncertainty is a question about information about processes, whether understood, random variations (known as «
noise» or stochastic processes), or systematic
model shortcomings (biases).
Using the broad
uncertainty you provide for the
models (weather
noise, etc.), I calculate that the T2LT and T2 means deviate from the
model means at the level of 1.25 and 1.26 (sigma - means), respectively.
Part of the
uncertainty in the attribution is of course how realistic the «
noise» in the
models is — and that can be assessed by looking at hindcasts, paleo - climate etc..
There are two classes of
uncertainty in
models — one is the systematic bias in any particular metric due to a misrepresentation of the physics etc, the other is
uncertainty related to weather (the
noise).
Some attribution assessments that link events to dynamically driven changes in circulation have been criticized on the grounds that small signal - to -
noise ratios,
modeling deficiencies, and
uncertainties in the effects of climate forcings on circulation render conclusions unreliable and prone to downplaying the role of anthropogenic change.
Let's compute the warming rate using each 30 - year segment of the Berkeley data, together with the estimated
uncertainty in that rate, using an ARMA (1,1)
model for the
noise just to feed the «
uncertainty monster.»
Although the first two sources of
model uncertainty - different climate sensitivities and regional climate change patterns - are usually represented in climate scenarios, it is less common for the third and fourth sources of
uncertainty - the variable signal - to -
noise ratio and incomplete description of key processes and feedbacks - to be effectively treated.
However, if a 5 dBA to 8 dBA increase in sound due to the proximity of the ocean were assumed and an additional + / − 3dBA were included to account for
model uncertainties,
noise levels may exceed 45 dBA.
One might, possibly, generate a single
model that generates an ensemble of predictions by using uniform deviates (random numbers) to seed «
noise» (representing
uncertainty) in the inputs.
And yes, it could easily be an even higher slope since we've used a white -
noise model, which underestimates the
uncertainty.
Here's the kicker: the
uncertainty in those trend rates is probably higher, perhaps by a substantial amount, because that graph is based on an AR (1)
model for the
noise.
Using an AR1
noise model, we find that these differences imply a 1σ
uncertainty in the acceleration of the instrument drift of 0.011 mm / y2.
They confused the
uncertainty in how well we can estimate the forced signal (the mean of the all the
models) with the distribution of trends +
noise.