...
the uncertainties in trend estimates using just data since 2000 are much larger than the trend estimates themselves.
She even computes
the uncertainty in that trend estimate (using fancy statistics), and uses that to compute what's called a «95 % confidence interval» for the trend — the range in which we expect the true warming rate is 95 % likely to be; it can be thought of as the «plausible range» for the warming rate.
For instance, he emphasizes that when computing
uncertainty in a trend estimate you have to take into account something called autocorrelation, which means the noise isn't the simple type called «white noise.»
Because the noise level at a single location is so large,
the uncertainty in the trend estimate at a single location will be large.
Well, if you start to take longer trends, then
the uncertainty in the trend estimate approaches the uncertainty in the expected trend, at which point it becomes meaningful to compare them since the «weather» component has been averaged out.
Not exact matches
First, the quality of the data is important: whether it is the LGM temperature
estimates, recent aerosol forcing
trends, or mid-tropospheric humidity — underestimates
in the
uncertainty of these data will definitely bias the CS
estimate.
Von Schuckmann & Le Traon (2011) also
estimate the errors
in global
trends from the period analysed, and also future error
uncertainty.
These measurements become sparser as we go further back
in time, hence
trend estimates become more uncertain; of course we fully accounted for this
uncertainty in our analysis.
This is not simply the
uncertainty in estimating the linear
trend, but the more systematic
uncertainty due to processing problems, drifts and other biases.
Have you computed the
uncertainty level
in your
estimate of the «decadal
trend»?
First, the quality of the data is important: whether it is the LGM temperature
estimates, recent aerosol forcing
trends, or mid-tropospheric humidity — underestimates
in the
uncertainty of these data will definitely bias the CS
estimate.
One
estimate of that error for the MSU 2 product (a weighted average of tropospheric + lower stratospheric
trends) is that two different groups (UAH and RSS) come up with a range of tropical
trends of 0.048 to 0.133 °C / decade — a much larger difference than the simple
uncertainty in the
trend.
Since you don't seem to know how meaningless «decadal
trends» are, you use the only data set that gives you what you want and ignore the others, and you act as though there's no
uncertainty in your «
trend»
estimate, your level of certainty amounts to nothing more than hubris.
Although there is still some disagreement
in the preliminary results (eg the description of polar ice caps), a lot of things appear to be quite robust as the climate models for instance indicate consistent patterns of surface warming and rainfall
trends: the models tend to agree on a stronger warming
in the Arctic and stronger precipitation changes
in the Topics (see crude examples for the SRES A1b scenarios given
in Figures 1 & 2; Note, the degrees of freedom varies with latitude, so that the
uncertainty of these
estimates are greater near the poles).
Her work explores observed
trends in droughts and heat waves and
estimating the
uncertainty associated with observations.
Uncertainties in the regression models and fits used to distinguish between periodic variations and
trends in the different databases appear to be a significant source of
uncertainty in the
estimates of longterm
trends.
To appreciate the issues involved
in comparing
estimates of surface and lower tropospheric temperature
trends, it is necessary to have at least a rudimentary understanding of these three kinds of measurements and the
uncertainties inherent
in each of them.
They are simply a first estimate.Where multiple analyses of the biases
in other climatological variables have been produced, for example tropospheric temperatures and ocean heat content, the resulting spread
in the
estimates of key parameters such as the long - term
trend has typically been signicantly larger than initial
estimates of the
uncertainty suggested.
Uncertainties of estimated trends in global - and regional - average sea - surface temperature due to bias adjustments since the Second World War are found to be larger than uncertainties arising from the choice of analysis technique, indicating that this is an important source of uncertainty in analyses of historical sea - surface
Uncertainties of
estimated trends in global - and regional - average sea - surface temperature due to bias adjustments since the Second World War are found to be larger than
uncertainties arising from the choice of analysis technique, indicating that this is an important source of uncertainty in analyses of historical sea - surface
uncertainties arising from the choice of analysis technique, indicating that this is an important source of
uncertainty in analyses of historical sea - surface temperatures.
The similarity of these observationally - based «NAO book - end»
trend maps with those derived directly from the leading EOF of the set of 40 CESM - LE SLP
trend maps (Fig. 2) attests to the robustness of the results, the utility of the method of Thompson et al. (2015) to
estimate uncertainty in trends from the statistics of a Gaussian time series, and the fidelity of CESM's simulation of the NAO.
In paleoclimate, if you want to know the certainty of the average trend in the blade of the stick, you wouldn't take the extremes of all the inputs to calculate uncertainty, you take the variance in the output and use some method i.e. monte carlo or a DOF estimat
In paleoclimate, if you want to know the certainty of the average
trend in the blade of the stick, you wouldn't take the extremes of all the inputs to calculate uncertainty, you take the variance in the output and use some method i.e. monte carlo or a DOF estimat
in the blade of the stick, you wouldn't take the extremes of all the inputs to calculate
uncertainty, you take the variance
in the output and use some method i.e. monte carlo or a DOF estimat
in the output and use some method i.e. monte carlo or a DOF
estimate.
These NAO «book - ends» provide an
estimate of the 5 — 95 % range of
uncertainty in projected
trends due to internal variability of the NAO based on observations superimposed upon model
estimates of human - induced climate change.
Because the differences between the various observational
estimates are largely systematic and structural (Chapter 2; Mears et al., 2011), the
uncertainty in the observed
trends can not be reduced by averaging the observations as if the differences between the datasets were purely random.
To
estimate the
uncertainty in an average or a
trend, all that is required is to calculate the average or
trend for each of the 100 realizations, and
estimate the
uncertainty from the distribution of the results.
The
uncertainty in the global mean sea level
trend is
estimated to be of ± 0.5 mm / yr
in a confidence interval of 90 % (1.65 sigma), whereas the
uncertainty of the regional mean sea level
trends is of the order of 2 - 3 mm / yr with values as low as 0.5 mm / yr or as high as 5.0 mm / yr depending on the region considered (Legeais et al., 2018, under review).
The very high significance levels of model — observation discrepancies
in LT and MT
trends that were obtained
in some studies (e.g., Douglass et al., 2008; McKitrick et al., 2010) thus arose to a substantial degree from using the standard error of the model ensemble mean as a measure of
uncertainty, instead of the ensemble standard deviation or some other appropriate measure for
uncertainty arising from internal climate variability... Nevertheless, almost all model ensemble members show a warming
trend in both LT and MT larger than observational
estimates (McKitrick et al., 2010; Po - Chedley and Fu, 2012; Santer et al., 2013).
That period 1995 - 2009 was just 15 years — and because of the
uncertainty in estimating trends over short periods, an extra year has made that
trend significant at the 95 % level which is the traditional threshold that statisticians have used for many years.»»
The models, note, only over
estimate recent temperature
trends by 18 %, half the expansion of the
uncertainty range - and that overestimation has been eliminated from the attribution by scaling
in any event.
The wedge labelled «
Estimated ARC
trend uncertainty» represents the spread of potential bias
in the satellite data relative to the end of the time series.
By the statistical evaluation of the different climate developments simulated, the
uncertainties in climate projections can be better
estimated and reduced, for example, for rainfall
trends.
Here's his argument: test each possible start year from 1990 through 2010, use just the data from then on to
estimate the
trend (the warming rate), and
estimate the
uncertainty in the
trend.
Figure 3.2: b) Observation - based
estimates of annual five - year running mean global mean mid-depth (700 — 2000 m) ocean heat content
in ZJ (Levitus et al., 2012) and the deep (2000 — 6000 m) global ocean heat content
trend from 1992 — 2005 (Purkey and Johnson, 2010), both with one standard error
uncertainties shaded (see legend).
These errors, as well as the influence of decadal and multi-decadal variability
in the climate, have been taken into account when
estimating linear
trends and their
uncertainties (see Appendix 3.
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.