Computer crimes

With Professor Shukla (and Kevin Trenberth) calling for sceptics to be put in the dock last week, it is perhaps unsurprising that a Guardian article on climate and the law provoked a bit of an overreaction. The article in question, by Adam Vaughan, was about a speech by prominent lawyer Philippe Sands and was entitled "World court should rule on climate science to quash sceptics, says Philippe Sands". This was taken by many to mean that sceptics should be prosecuted, particularly as the standfirst then read "International Court of Justice ruling would settle the scientific dispute and pave the way for future legal cases on climate change, says high-profile lawyer".

However, examination of the text of Sands' speech reveals that the Guardian headline writers had actually been playing a little fast and loose with the facts. What Sands actually wants is for the international courts to rule on some of the scientific questions surrounding the global climate. He gave as examples the following:

A first tier of issues might include: is climate change underway? have sea-levels risen? Have anthropogenic greenhouse gas emissions been the main cause of atmospheric warming?

Click to read more ...

The night remains dark

As the latest paper to try to explain the pause appears, it's hard not to smile. Reason follows explanation follows rationale follows excuse, and the interested layman is left with the abiding impression that the night remains very very dark indeed.

This is not to say that these are not valiant efforts to get to the bottom of things, but let us not kid ourselves, a la Guardian, that anyone really has much of a clue about what is going on yet. Claims that climate models are even more accurate than previously thought are the scientific equivalent of a fart joke and deserve the same response.

Click to read more ...

The first five years of the RCPs

Further to yesterday's post on butterflies and RCPs, I wondered just how things were panning out for the RCPs since they were issued five years ago. I wasn't really expecting very much from this analysis since five years is not very long, but it turned out that there is more of a difference than might be expected.

The RCP data is for the mid-year carbon dioxide concentration and it turns out that the June figure from Mauna Loa has just tipped the 400ppm mark. RCP8.5 predicted that 2015 would be the first year in which the 400ppm mark was breached at the mid-year point, so at first glance we are indeed on the RCP8.5 pathway.

Click to read more ...

Thoughts on aerosols

I've been reading a bit about aerosols in recent days. As many BH readers will know, these are one of the great uncertainties in the Earth's climate and so they crop up all the time.

This interest was provoked in part by a conversation I was having with Ed Hawkins about his new paper. I had invoked Bjorn Stevens' study from which it is possible to infer a value of -0.5 Wm^-2 for the overall effect of aerosols, around half of the IPCC's best estimate of -0.9 Wm^-2. This of course would imply that climate sensitivity would have to be much lower than the IPCC suggests it is.

Click to read more ...

Apples, oranges, whatever...

A new paper by Kevin Cowtan et al claims that the divergence of models and observations is not as big as we thought.

Global mean temperatures from climate model simulations are typically calculated using surface air temperatures, while the corresponding observations are based on a blend of air and sea surface temperatures. This work quantifies a systematic bias in model-observation comparisons arising from differential warming rates between sea surface temperatures and surface air temperatures over oceans. A further bias arises from the treatment of temperatures in regions where the sea ice boundary has changed. Applying the methodology of the HadCRUT4 record to climate model temperature fields accounts for 38% of the discrepancy in trend between models and observations over the period 1975-2014.

It sounds a bit odd to me, but I don't have a copy as yet, so I'm going to hold off further comment for the minute. One assumes though that even if the findings are sound the divergence of satellite temperatures from the models is unaffected.

Update on Jul 30, 2015 by Bishop Hill

Thanks to readers who have sent the paper along. Here's what the authors have done:

Global averages of the observational temperature records are typically compared to near surface air temperature from an ensemble of climate model simulations...most studies have used the surface
air temperature field from models rather than blended land-ocean temperatures...A true like-with-like comparison would involve blending the air and sea surface temperature fields from the models in a manner consistent with the observational records. The purpose of this work is to evaluate the impact of comparing air temperatures from models with the blended observational data, and to establish guidelines for the determination of blended temperature comparisons.

This seems unexceptionable to me.

Met Office still brazen

Readers may recall the paper I wrote for GWPF on the problems with the UKCP09 climate projections. These were demonstrably unreliable: the predictions were formulated as a weighted average of possible future climates, but it was discovered that only unrealistic future climates were taken into account. Readers may also recall that this has all been acknowledged by the Met Office, but that they are refusing to acknowledge that it is a problem.

Astonishing then to see that the Met Office is still pushing UKCP09, with a new paper in Nature Climate Change, dutifully (and inevitably) picked up by the BBC:

Click to read more ...

Why science is not enough

There's an excellent take-down of the "evidence-based policy" movement at SciDevNet. Author Erik Millstone seems to have a pretty firm grasp of things:

...the relevance of...models is more often assumed than it is demonstrated. In the case of climate change, some computer models of the impact of greenhouse gases on climate might usefully approximate to global realities.

Science advisers often ignore or conceal key uncertainties when offering judgements, perhaps catering to policymakers’ preference for reassuring oversimplifications

...some stakeholders might claim a uniquely authoritative understanding of an issue based on evidence

The GISS graph mystery

There are lots of people getting excited by a new animation put out by Bloomberg, which seeks to persuade people that only carbon dioxide can explain the temperature history of the last century or more. It's nothing new - just a prettier version of arguments that have been put forward in the past. I have to say I am greatly amused by the fact that the models stop in 2005. I wonder why that could be?

The simulation was put together by Gavin Schmidt and Kate Marvell of GISS, using GISS Model E2, a climate simulator with a relatively low TCR of 1.5 but a rather strong aerosol forcing of -1.65 Wm^-2. However, the IPCC's best estimate of aerosol forcing is only -0.9 Wm^-2 and the recent Bjorn Stevens paper put the figure at just -0.5 Wm^-2. What this means is that had the GISS model had an aerosol forcing in line with recent best estimates, it would have warmed much too quickly. The resulting embarrassment would have been greater still had the model data not ended ten years ago. I really would like to know why this is.

Still, it's a pretty graph.

Update on Jun 26, 2015 by Bishop Hill

Barry Woods points out a tweet by the Met Office's Peter Thorne, who says that the GISS Model E2 simulations stop in 2005 and were not extended by most groups.

I wonder why.

Update on Jun 26, 2015 by Bishop Hill

Nic Lewis emails to say that the GISS webpage is wrong. The aerosol forcing behind the Bloomberg page was in line with the AR5 best estimate, although still much stronger than the Bjorn Stevens estimate. However, the TCR was also even lower, at only 1.4, similar to the Lewis estimate (1.35) based on the AR5 aerosol figure. 

So we have a model that is not very sensitive to carbon dioxide, and which appears to reproduce past temperature history. But if Stevens' aerosol estimate is correct, then it's still too sensitive.

Texas models

There has been a bit of flooding in Texas and, with weary inevitability, the activist-inclined press are wondering about connections to climate change. The Conversation US has invited Texas state climatologist John Nielson-Gammon to explain and to be fair he makes a reasonable fist of it, but there is still the usual tendency to discuss climate model outputs in their current state of disarray as if they were meaningful. Take this for example:

Studies have shown the odds of very intense rainfall in this part of the country have gone up substantially over last century. The cause and effect with climate change and surface temperature is fairly direct. There’s definitely a connection there.

No there isn't. Climate models have little ability to predict rainfall, and none at all at local levels. Even the IPCC describes their abilities in this area as "modest". If there is "definitely" a connection, if the thermodynamics are so simple, why do climate models do so badly?

Why do people believe stupid things?

Jose Duarte continues to mine a productive seam on the shameful behaviour of, on the one hand John Cook and his team, and on the other Stephan Lewandowsky. His post a couple of days ago was on the subject of the true value of the climate consensus and he puts the proportion of climate scientists who think that most warming is caused by carbon dioxide at 80%. I had previously thought that the true figure was around the 75% mark, so we are in the same ballpark.

But as Judith Curry points out in an update to Jose's post, this is all slightly beside the point. Many or even most of the the people who call themselves climate scientists are not actually working on anything relevant to the question at hand - they are specialists in impacts and responses and the like. They only believe that most warming is caused by carbon dioxide because their colleagues specialising in the atmospheric sciences tell them so.

Click to read more ...

Slow news day

It's a slow news day so far today, so I'll go with a Guardian-talking-drivel-on-climate story, which is a bit like a Pope-is-Roman-Catholic story, but can occasionally provide some light relief. Today's headline from the fount of foolishness is 

Extreme weather already on increase due to climate change, study finds.

Unfortunately for the Guardian, the study in question, by Fischer and Knutti, is actually nothing to do with observations of extreme weather at all. Instead it is about their attribution to humankind. You have to wonder whether the headline writers even read the paper.

And if you look at the study, it turns out to be just an extension of the use-shonky-GCMs-to-blame-humankind approach adopted by others in the past.  I'm hugely amused by its suggestion that GCMs, which have precisely zero ability to predict precipitation, can be used to show that "18% of moderate daily precipitation extremes over land are attributable to the observed temperature increase since preindustrial times". Particularly since in the IPCC's view it's hard to find any evidence of changes in extreme weather anyway.

It's like...magic.

The Iris Hypothesis from the archives

Today, most mainstream researchers consider Dr. Lindzen’s theory discredited.

Justin Gillis in the New York Times

...the basis of Lindzen’s argument, which itself is the basis of all remaining relatively credible climate contrarianism, is entirely false...

Dana Nuccitelli

You have people who keep propping [the discredited theory] up,...Lindzen may still hold to it, but no one would still be listening to him. He wouldn't be given a platform.

Prof Joel Norris of Scripps

Refuted by four peer-reviewed studies within a year of the publication of Lindzen's hypothesis.

Nuccitelli again

Iris hypothesis bridges model-observation gap

Some months ago I picked up wind of a new paper that was going to provide some support for Richard Lindzen's Iris Hypothesis - the idea that in a warming planet there would be reduced levels of cirrus cloud, which would allow the extra heat to escape from Earth.

The paper in question seems to be this one, published in Nature Geoscience. The authors are Bjorn Stevens and Thorsten Mauritzen, the former the author of a much-discussed paper on aerosols and the latter best known for his paper on the subject of GCM tuning.

Here's the abstract:

Missing iris effect as a possible cause of muted hydrological change and high climate sensitivity in models

Equilibrium climate sensitivity to a doubling of CO₂ falls between 2.0 and 4.6 K in current climate models, and they suggest a weak increase in global mean precipitation. Inferences from the observational record, however, place climate sensitivity near the lower end of this range and indicate that models underestimate some of the changes in the hydrological cycle. These discrepancies raise the possibility that important feedbacks are missing from the models. A controversial hypothesis suggests that the dry and clear regions of the tropical atmosphere expand in a warming climate and thereby allow more infrared radiation to escape to space. This so-called iris effect could constitute a negative feedback that is not included in climate models. We find that inclusion of such an effect in a climate model moves the simulated responses of both temperature and the hydrological cycle to rising atmospheric greenhouse gas concentrations closer to observations. Alternative suggestions for shortcomings of models — such as aerosol cooling, volcanic eruptions or insufficient ocean heat uptake — may explain a slow observed transient warming relative to models, but not the observed enhancement of the hydrological cycle. We propose that, if precipitating convective clouds are more likely to cluster into larger clouds as temperatures rise, this process could constitute a plausible physical mechanism for an iris effect.

Important paper alert

Judith Curry is discussing a new paper by Stephens et al, published in Reviews of Geophysics. As one commenter below the thread put it, his "this is an important paper" alarm was triggered, and having read it myself I agree.

Here's the abstract:

The fraction of the incoming solar energy scattered by Earth back to space is referred to as the planetary albedo. This reflected energy is a fundamental component of the Earth’s energy balance, and the processes that govern its magnitude, distribution, and variability shape Earth’s climate and climate change. We review our understanding of Earth’s albedo as it has progressed to the current time and provide a global perspective of our understanding of the processes that define it. Joint analyses of surface solar flux data that are a complicated mix of measurements and model calculations with top-of-atmosphere (TOA) flux measurements from current orbiting satellites yield a number of surprising results including (i) the Northern and Southern Hemispheres (NH, SH) reflect the same amount of sunlight within ~ 0.2Wm2. This symmetry is achieved by increased reflection from SH clouds offsetting precisely the greater reflection from the NH land masses. (ii) The albedo of Earth appears to be highly buffered on hemispheric and global scales as highlighted by both the hemispheric symmetry and a remarkably small interannual variability of reflected solar flux (~0.2% of the annual mean flux). We show how clouds provide the necessary degrees of freedom to modulate the Earth’s albedo setting the hemispheric symmetry. We also show that current climate models lack this same degree of hemispheric symmetry and regulation by clouds. The relevance of this hemispheric symmetry to the heat transport across the equator is discussed.

The idea that the albedo is buffered in some way seems important to me and it goes without saying that the inability of climate models to reproduce the buffering represents a critical failing. Changes in albedo are supposed to be an important part of the enhanced greenhouse effect that is supposed to produce rapid warming but hasn't. To some extent therefore, it may be that albedo buffering is a factor in the models' ever-increasing divergence from reality.

Pielke Sr calls the paper a landmark. I don't think he's wrong.

The full paper is available here.

Climate Change by Numbers

Updated on Mar 3, 2015 by Bishop Hill

I almost gave up on Climate Change by Numbers last night. By ten o'clock I was flagging fast and not really getting a lot from it which is a pity because it could have been brilliant.

The presentation was really well done. I thought the decision to have three different presenters paid off in spades and the producers did well to come up with three such engaging people - Norman Fenton, Hannah Fry and David Spiegelhalter - to front the show. I liked the style of having them completely separate and avoiding the cheesy infills that TV people seem to like so much. The decision to get just a little bit closer to the maths was a good one and the radical step of showing equations on screen seemed like a bit of a breakthrough.

Click to read more ...