Now, researchers with World Weather Attribution have carried out a multi-method analysis to assess the role of warming connected to human activities in these record temperatures.
"We simulate what is the possible weather under the current climate and then we simulate what is the possible weather without anthropogenic climate change, and then we compare these two likelihoods which gives us the risk ratio," Dr Friederike Otto from the University of Oxford, one of the study's authors, told BBC News.
"We found a very strong signal."
That signal, according to the authors, made heat waves at least 10 times more likely in Spain and Portugal.

To include parameter uncertainty into probabilistic climate forecasts one must first specify a prior.
We advocate the use of objective priors, and, in particular, the Jeffreys’ Prior. In previous work we
have derived expressions for the Jeffreys’ Prior for the case in which the observations are independent
and normally distributed. These expressions make the calculation of the prior much simpler than
evaluation directly from the definition. In this paper, we now relax the independence assumption and
derive expressions for the Jeffreys’ Prior for the case in which the observations are distributed with
a multivariate normal distribution with constant covariances. Again, these expressions simplify the
calculation of the prior: in this case they reduce it to the calculation of the differences between the
ensemble means of climate model ensembles based on different parameter settings. These calculations
are simple enough to be applied to even the most complex climate models.

We argue that it would be desirable to use Jeffreys’ priors in the construction of numerical model
based probabilistic climate forecasts, in order that those forecasts could be argued to be objective.
Hitherto, this has been considered computationally unfeasible. We propose an approximation that
we believe makes it feasible, and derive closed-form expressions for various simple cases.

I got this email today as well, however all my work units appear to be fine, scanning through the stderr_um files, there all 0 bytes.

I\'m not sure what to do?

Here\'s my clientID

http://climateapps2.oucs.ox.ac.uk/cpdnboinc/results.php?hostid=924187

However this presentation
http://www.climateprediction.net/science/pubs/allen_NOC2007.pdf
may give you a flavour of what they are arguing. (Edit 14Mb download)

Our basic point in the Perspectives piece is that it\'s probably a mistake to fix a concentration target now, based on some subjective estimate of climate sensitivity. As long as our policy people are allowed to bootstrap their targets occasionally we don\'t really ever need to know the exact value of climate sensitivity very well.

In essence, what Roe and Baker show is that this characteristic shape arises from the non-linear relationship between the strength of climate feedbacks (f) and the resulting temperature response (deltaT), which is proportional to 1/(1-f). They show that this places a strong constraint on our ability to determine a specific \"true\" value of climate sensitivity, S. These results could well be taken to suggest that climate sensitivity is so uncertain as to be effectively unknowable. This would be quite wrong.

Perspectives
ATMOSPHERE:
Call Off the Quest
Myles R. Allen and David J. Frame
Knowledge of the long-term response of Earth\'s climate to a doubling of atmospheric carbon doixide may be less useful for policy-makers than commonly assumed.