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The extraordinary attempts to prevent sceptics being heard at the Institute of Physics
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Entries in Climate: Models (240)

Tuesday
May282019

An attack that is nothing of the sort

Yesterday, the New York Times got rather upset over changes to President Trump’s climate policy, which it represented a hardening of his “attack on climate science”.

Interestingly though, you have to read quite a lot of words before you actually get to the point – usually a sure sign that there is actually nothing much by way of news and quite a lot by way of hand waving. It turns out that Trump’s attempt to “undermine the very science on which climate change policy rests” is down to this:

[Director of the US Geological Survey,] James Reilly, a former astronaut and petroleum geologist, has ordered that scientific assessments…use only computer-generated climate models that project the impact of climate change through 2040, rather than through the end of the century, as had been done previously.

To describe this as an “attack” is obviously absurd. Reasonable people can question the ability of climate models to give us useful information about the climate in 20 years’ time, let alone 80. In a GWPF paperpublished last week, it was pointed out that climate models are overestimating warming in the tropical troposphere by a factor of three. With errors of that magnitude, how much trust can we really put in projections for the end of the century? You would have to be quite an innocent to take them at face value.

In another GWPF paper Professor Judith Curry points out that the climate may be fundamentally beyond our ability to predict it:

Arguably the most fundamental challenge with [climate models] lies in the coupling of two chaotic fluids: the ocean and the atmosphere. Weather has been characterised as being in state of deterministic chaos, owing to the sensitivity of weather forecast models to small perturbations in initial conditions of the atmosphere…A consequence of sensitivity to initial conditions is that beyond a certain time the system will no longer be predictable; for weather this predictability timescale is a matter of weeks.

To describe the President as “attacking” climate science when he doubts projections out to the end of the century is therefore clearly nonsense. Indeed, he should probably be congratulated for recognising the powerlessness of the field in the face of an overwhelmingly complex climate system.

Monday
Dec122016

Use and abuse of climate simulations

Some of you may be interested in Gavin's Schmidt's forthcoming talk  at Exeter University. It's hard to deny his expertise in the area.

Climate change is now a constant presence in the media with many stories about the latest records in global heat, Arctic ice loss, sea level rise, or the potential for changes in extreme weather. But many people still have questions about how scientists study the Earth system, where the dramatic predictions of future change come from, and how credible they are.

In this talk Dr Schmidt will discuss the use and abuse of climate simulations, how they are used to attribute changes in the past and what they suggest for the future. He will specifically discuss how global society now has to choose its own adventure and what the implications of these choices will be.

Details here.

Thursday
Feb252016

Quote of the day, predictability edition

Even a fully deterministic system is fully unpredictable at climatic timescales when there is persistence.

From a Demetris Koutsoyiannis presentation.

Tuesday
Feb232016

Two worlds collide

GWPF have release a very interesting report about stochastic modelling by Terence Mills, professor of applied statistics and econometrics at Loughborough University. This is a bit of a new venture for Benny and the team because it's written with a technical audience in mind and there is lots of maths to wade through. But even from the introduction, you can see that Mills is making a very interesting point:

 

The analysis and interpretation of temperature data is clearly of central importance to debates about anthropogenic globalwarming (AGW). Climatologists currently rely on large-scale general circulation models to project temperature trends over the coming years and decades. Economists used to rely on large-scale macroeconomic models for forecasting, but in the 1970s an increasing divergence between models and reality led practitioners to move away from such macro modelling in favour of relatively simple statistical time-series forecasting tools, which were proving to be more accurate.
In a possible parallel, recent years have seen growing interest in the application of statistical and econometric methods to climatology. This report provides an explanation of the fundamental building blocks of so-called ‘ARIMA’ models, which are widely used for forecasting economic and financial time series. It then shows how they, and various extensions, can be applied to climatological data. An emphasis throughout is that many different forms of a model might be fitted to the same data set, with each one implying different forecasts or uncertainty levels, so readers should understand the intuition behind the modelling methods. Model selection by the researcher needs to be based on objective grounds.

There is an article (£) in the Times about the paper.

I think it's fair to say that the climatological community is not going to take kindly to these ideas. Even the normally mild-mannered Richard Betts seems to have got a bit hot under the collar.

 

 

 

Wednesday
Feb102016

Tail wind

I once faced off against Paul Williams of Reading University in a radio debate. He came across as a pretty rational kind of guy and we had a nice exchange of emails afterwards. But I have to say that his most recent paper is one of those ones that make you despair with their sheer futility. Here's the BBC take on it.

Flights from the UK to the US could take longer due to the changes in the climate, according to a new study.

Global warming is likely to speed up the jet stream, say researchers, and slow down aeroplanes heading for the US.

While eastbound flights from the US will be quicker, roundtrip journeys will "significantly lengthen".

It's published in Environmental Research Letters, which is usually not a good sign. The authors apparently fed "synthetic atmospheric wind fields generated from climate model simulations into a routing algorithm of the type used operationally by flight planners" and deduced that westbound transatlantic flights were going to take longer while eastbound flights will be faster. But, almost inevitably, the losses are expected to outweight the gains.

I wonder what evidence there is that GCMs can predict, or even hindcast, changes in wind speeds in a warming world? 

Monday
Jan252016

A "substantial" error in GISS Model E

Over the weekend Nic Lewis posted a brief update to his latest posting on the Marvel et al paper. In it, he described something he had unearthed in a paper by Chandler et al. I've reproduced it here.

I have just discovered (from Chandler et al 2013) that there was an error in the ocean model in the version of GISS-E2-R used to run the CMIP5 simulations. The single forcing simulations were part of the CMIP5 design, although it is possible that some or all of them were run after the correction was implemented.

Chandler et al write:

Click to read more ...

Friday
Jan222016

The daft and the non-daft climate model runs

Nic Lewis has published another fascinating article about the Marvel et al paper over at Climate Audit. I was particularly taken by the discussion of the GCM runs that lay behind Marvel et al's assessment of the effect of land-use changes.

In essence, the authors did five runs of the model, with only land-use forcing changes. This tends to produce a cooling, and four of the runs gave similar results, with their average looking like this:

But one looked entirely different; like this:

Click to read more ...

Thursday
Jan212016

Real-world efficacies

BH readers have long been aware that low estimates of climate sensitivity based on observations are little affected by the pause and will therefore be little affected by this year's El Nino either. The discussion in this area will continue to focus on subjects like efficacies and aerosols. Marvel and colleagues are apparently formulating a response to Nic Lewis's critique, which is sure to be interesting. While we're waiting, I have been passed a preprint of a forthcoming Piers Forster paper in Annual Review of Earth and Planetary Sciences, which makes some interesting observations on the efficacy debate.

Click to read more ...

Tuesday
Dec152015

The extraordinary climate effect of land-use change

The latest attempt to conjure up a hypothesis as to why things are going to get much worse on the climate front has appeared in Nature Climate Change, with an author team including Gavin Schmidt and Kate Marvel.

The paper delves deeper into the idea of forcing efficacy, a concept that is explained as follows:

The concept of radiative forcing is used to compare the effects of different physical drivers on the Earth's energy budget. Two forcing agents that produce a similar radiative imbalance might be expected to initiate similar feedbacks and have the same global mean temperature response. However, there can be variations in the size and type of feedbacks engendered by a specific forcing, mainly due to geographical variations in the forcing magnitude. These variations can be characterized by an efficacy that scales for the differences in temperature response. Forcings that project more strongly on the Northern Hemisphere, land or polar regions are systematically more effective at changing temperatures than an equivalent amount of CO2, whose forcing is more uniformly distributed throughout the globe. The converse is true for forcings localized in the Southern Hemisphere or ocean regions.

Click to read more ...

Friday
Dec112015

More problems for the climate models

As I noted in my Spectator piece yesterday, the Met Office is really, really desperate to attribute floods and rainfall to global warming, particularly at this time of year when they can usually rely on taking advantage of a bit of human misery.

Unfortunately, some toad at the Lawrence Livermore laboratories in the US has rather gone and pooped the party by publishing a paper that shows that climate models are overestimating growth in rainfall (report here).

Lawrence Livermore researchers and collaborators have found that most climate models overestimate the increase in global precipitation due to climate change.

Specifically, the team looked at 25 models and found they underestimate the increase in absorption of sunlight by water vapor as the atmosphere becomes moister, and therefore overestimate increases in global precipitation.

The team found global precipitation increase per degree of global warming at the end of the 21st century may be about 40 percent smaller than what the models, on average, currently predict.

They are not the first to notice how bad climate models are, but it's good to be reminded of these things, particularly when there's rain - and the odd chief scientist - in the air.

Monday
Nov232015

Exxon knew what the IPCC didn't

Bernie Lewin has posted another of his must-read climate history pieces, this time looking at the history of claims about detection and attribution of temperature changes to mankind. His point is that claims that "Exxon knew" back in the 1970s are absurd when set in the context of what climate science was saying on the subject of an anthropogenic influence ten, or even twenty years later.

It's beautifully written and confirms Bernie's place as an important historian of global warming science. You must be able to get a very comical juxtaposition by reading Bernie's erudite thoughts after perusing the effusions of a "proper" historian like Naomi Oreskes.

 

Thursday
Oct152015

Don't blame the sulphates

A new paper in Climate Dynamics examines the hypothesis that the indirect effects of aerosols (aka pollution) has been behind the hiatus/pause/thing-with-no-name/non-existent-thing that has, or has not, been affecting the global temperature average for the best part of two decades.

Andrew Gettelmann and colleagues focus on sulfate aerosols and plug revised forcing figures into climate models to see if this can bridge the gap to the temperature records. Unfortunately the answer seems to be a pretty firm "no".

 

Sulfate aerosol emissions increase globally from 2000 to 2005, and then decrease slightly to 2010. Thus the change in anthropogenic sulfate induced net global radiative forcing is small over the period. Sulfate ACI might be a contributor to the spatial patterns of recent temperature forcing, but not to the global mean ‘hiatus’ itself.

 

Of course there is always the possibility - or likelihood - that the models just can't simulate the cloud-aerosol interactions properly. Nevertheless, if they do then another explanation for the pause has been ticked off and the mystery deepens.

Monday
Oct052015

Puffed rice

Here's an interesting wrinkle in climate science that I hadn't thought about before. It came up in a thread at Ken Rice's place, underneath an article about carbon dioxide reductions.

The specific claim of interest was that "the amount of warming depends almost linearly on cumulative emissions". This is a claim that you hear quite often, with the corollary being that even if we halt carbon dioxide emissions, temperatures are going to remain high for centuries. However, it seems that the scientific veracity of the statement is not exactly set in stone, as Nic Lewis points out in the comments.

For the record, whilst this may be true for simulations by most current Earth system models, it is an entirely model dependent result. So please don’t present it as if a fact. If one builds a model with a low ECS, and moderate climate-cycle feedbacks, warming peaks immediately if emissions cease and declines quite rapidly thereafter. Which would happen in the real climate system is not as yet known, of course.

Click to read more ...

Thursday
Oct012015

Climate cool-aid

Via El Reg, we discover that a whole new source of climate coolants has been discovered.

A team of top-level atmospheric chemistry boffins from France and Germany say they have identified a new process by which vast amounts of volatile organic compounds (VOCs) are emitted into the atmosphere from the sea - a process which was unknown until now, meaning that existing climate models do not take account of it.

The coolant in which they are interested is isoprene, which was previously thought to be produced mainly by marine plankton. It now seems that it can be produced abiotically too, and in quantities that might even explain the model-observation divergence.

As with the last story, I'd suggest a measure of caution might be valuable.

Saturday
Sep262015

Great Evans above

Jo Nova carries a rather interesting piece today about some work done by her husband David Evans, who thinks he has uncovered a rather major flaw in the mathematics at the core of the basic model of the climate.

The climate models, it turns out, have 95% certainty but are based on partial derivatives of dependent variables with 0% certitude, and that’s a No No. Let me explain: effectively climate models model a hypothetical world where all things freeze in a constant state while one factor doubles. But in the real world, many variables are changing simultaneously and the rules are  different.

Partial differentials of dependent variables is a wildcard — it may produce an OK estimate sometimes, but other times it produces nonsense, and ominously, there is effectively no way to test. If the climate models predicted the climate, we’d know they got away with it. They didn’t, but we can’t say if they failed because of a partial derivative. It could have been something else. We just know it’s bad practice.

This sounds plausible to me. What do readers here think?