Big global warming meeting in Canada

[EternalOptimist]

Travesty.

There, I engaged.

which ones are wrong then ?

[pjclarke]

<Sigh> They will all prove to be 'wrong' in the long term, barring a miraculous coincidence. Nobody knows how greenhouse gas concentrations will evolve and so they are run for various scenarios. Ensembles of these runs are the averaged together, and published with a confidence interval. A common trick amongst the fake sceptics is to just compare the most extreme scenario with obervations to show the models are too 'hot'.

Your example would be better phrased as 'I think Rolls Royce will be in the range x to y in 2020 years, with 95% certainty. If you're asking my opinion I think scenario RCP6.5 is most likely.

Also, the models are physics-based and so are changed as our understanding of the climate physics changes. For example the model used by Hansen for his 1988 projections had a property that a doubling of CO2 resulted in a rise of around 4C, more recent models put it nearer 3C. This has a small effect in the early years but will means the model will overstimate after a couple decades. But he didn't do too bad ...

[BlasterBates]

Thanks pj though I noticed that it is somewhat out of date, by around 8 or 9 years. Time marches on so lets look how the comparison has panned out in the intervening years.




Have a nice weekend

[pjclarke]

Well, thanks in return, but without knowing which models are being plotted, and for which scenario the comparison is meaningless. Can you tell us? I'm sure Christy and Spencer would never cherry-pick the warmest models, with no uncertainty and the coolest observations to make a bogus point now would they?

Quark Soup by David Appell: Speaking of "Epic Fails"

Not had much joy in the past but hope springs eternal, which models, and which scenario BB?

[pjclarke]

An apples-to-apples comparison. Details here.

You're welcome.

[BlasterBates]

An update to your previous graph comparing against Hansen's predictions:



By posting the link you've scored an own goal because it's a continuation of the exact same graph you posted which looked gr8 in 2005 but shows how wrong the prediction is in 2012.

[pjclarke]

And bang goes the theory that climate scientists hide adverse results. I invite you to re-read what I wrote about Hansen 1988. As I said, the physics in the 1988 model have since been improved, up to date models have a lower sensitivity. The fact that the 1988 model is now running hot is evidence that the lower figure is accurate, and the text in the article shows that the IPCC CIMP3 models for the same period get the trend right to within uncertainty bounds ...

What do we learn from James Hansen's 1988 prediction?

Any joy in tracking down which models and scenario were plotted in the graph you shared?

[BlasterBates]

And bang goes the theory that climate scientists hide adverse results. I invite you to re-read what I wrote about Hansen 1988. As I said, the physics in the 1988 model have since been improved, up to date models have a lower sensitivity. The fact that the 1988 model is now running hot is evidence that the lower figure is accurate.

What do we learn from James Hansen's 1988 prediction?

Any joy in tracking down which models and scenario were plotted in the graph you shared?

Global Warming Slowdown: The View from Space « Roy Spencer, PhD

Voila....

As you can see not looking good for the models.

[pjclarke]

Yeah, I know where you got the graph, that's why I said Spencer and Christy. But the text does not specify the models used or the scenarios. This strikes me as the very lack of transparency complained of above. All he says are that they 'approximately represent' the models used by the IPCC.

Why did he not show the actual IPCC models, I wonder?