Archive for the ‘Skeptics’ Category

A warm 2015 and model –data comparisons

August 7, 2015

Guest post by Jos Hagelaars. Dutch version is here.

Discussions on the Internet regarding climate change are sometimes about scientific details, sometimes about the climate sensitivity regarding the equilibrium situation hundreds of years from now, but the most prevalent discussion topic is probably: the global average temperature. Will it get warmer or colder, is there a temporary slowdown or acceleration in the rise in temperature, are the models correct or not, will the eventual warming of our earth in the future be large or small? New numbers are released on a monthly basis and every month megabytes of text are generated about them. My forecast is that 2015 again will lead to a discussion-spike.

The graph above shows the evolution of the global surface temperature anomaly for three datasets, where the average of the period 1981-2010 is defined as 0. For the year 2015 only data are presented up to and including June. So far 2015 exceeds all other years and the evolving El Niño makes it likely that 2015 will set a new world record.
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Climate researcher Bart Strengers wins wager with climate sceptic Hans Labohm

January 23, 2015

Guestpost by Bart Strengers. Originally appeared as a news item on the PBL website.

Late 2009, in the run-up to the international climate conference in Copenhagen, PBL climate researcher Bart Strengers had an online discussion with climate sceptic Hans Labohm on the website of the Dutch news station NOS (in Dutch). This discussion, which was later also published as a PBL report, ended in a wager. Strengers wagered that the mean global temperature over the 2010–2014 period would be higher than the mean over 2000 to 2009. Hans Labohm believed there would be no warming and perhaps even a cooling; for example due to reduced solar activity.

At the request of Labohm, it was decided to use the UAH satellite temperature data set on the lower troposphere (TLT) (roughly the lowest 5 km of the atmosphere). These data sets are compiled by the University of Alabama in Huntsville. Satellites are used to measure radiation in the atmosphere, after which the temperature of the various layers of the atmosphere is derived using a complex algorithm.

According to the UAH today, temperatures appear to have been an average 0.1 °C warmer over the past five years than over the 10 years before that. Thus, Strengers has won the wager. The stakes: a good bottle of wine.

PBL temp comp Eng - 0040_001g_adhoc
The UAH temperature series since 1979 (no satellites were available for the period before then). The green lines represent the mean over periods of 10 years. The purple line on the far right is the mean over the 2010–2014 period.
UAH satellite data series shows the greatest warming

Precisely these UAH data, incidentally, show by far the most warming. The 4 other main global temperature series also show warming over the last 5 years, but one that is markedly lower (between 0.03 and 0.05 °C).

What causes the differences between the data series?

The table below shows the global warming, in °C, over the past 5 years, compared to the 10 years before that, for the five main global temperature series: the satellite series of the University of Alabama in Huntsville (UAH) and of the Remote Sensing Systems (RSS), and the surface temperature series of NASA, Climate Research Unit (CRU) and the National Climatic Data Centre (NCDC). CRU’s series are based on surface temperature measurements up to and including November 2014, as data on December were not yet available.

The large difference (by more than a factor of 3!) between the UAH and RSS satellite series is remarkable (also see the graph below). According to the UAH team, in which two well-known climate sceptics are involved, the difference is mainly caused by the fact that RSS partly bases its series on an old satellite (NOAA-15) with an increasingly lower orbit around the earth. This causes an error in measurements that is insufficiently corrected by RSS. All in all, it is a technical and complex issue, which possibly causes the differences, but it mainly shows how complicated the procedure is for determining global temperatures on the basis of satellite measurements. The three surface measurement series provide a much more consistent image of between 0.04 °C and 0.05 °C warming.

Satellite temperature measurements difficult to compare with surface measurements

In addition, it is important to note that satellite and surface measurements are difficult to compare. This is due to the fact that satellite series are based on the temperature of the entire lower troposphere (the lowest 5 km of the atmosphere). The temperature of this atmospheric layer is, for example, much more sensitive to El Niños than surface temperatures are. This is illustrated in the graph below by the relatively high peak for the two satellite series at the time of the super El Niño in 1997–1998 and the less strong El Niño of 2010. The reverse is the case for La Niñas, such as the strong one of 2008; here, satellite series typically show a lower temperature.

PBL - temp comp - 0040_002g_adhoc
Temperatures according to 2 satellite series (UAH and RSS). The purple line indicates the mean of the three surface temperature series. The satellite series show peaks in 1998 and 2010, as a result of El Niño, which are greater than those in the surface temperature series. The low satellite value for 2008 coincides with the opposite of an El Niño: La Niña. Note how the last 4 years in the RSS series are far below those in the other series. According to the surface temperature measurements, 2014 was the warmest year on record!

The graph shows that the last years in the RSS series clearly deviate from the other temperature series, with lower values of over 0.1 °C. This suggests that RSS rather than UAH is too low (as also claimed by the UAH team). The outcome of this discussion may lead to adjustments to one or both satellite series, as has been done in the past, particularly to the UAH series, on numerous occasions.

The surface temperature series further indicate that 2014 was the warmest year on record, even without an El Niño!

Contribution by cooling and warming influences.

Strengers indicated at the time that ‘in light of the scientific uncertainties, I may lose, but this is not likely to happen’. He gave four reasons why a possible reduction in warming, or even a cooling could occur. Bold indicates that the related reason more or less became a reality over the past 5 years.

  • a continued (relatively) low solar activity;
  • a relatively high heat absorption by the (deep) oceans;
  • a period of cooling due to incidental variations in the climate;
  • lower climate sensitivity than expected.

In addition, Strengers gave three reasons why he nevertheless expected to win:

  • a further increase in greenhouse gas concentrations in the atmosphere;
  • the ‘best-estimate’ by the IPCC is that of a warming of 0.2 °C per decade;
  • the chances of overestimating climate sensitivity are smaller than those of underestimation.

The sum of all factors, thus, has led to continued warming. Below each of these factors is explained in more detail.

Continued (relatively) low solar activity

Over the past 5 years, the reduced solar activity has continued and, thus, likely also has slightly reduced global warming over that period. In the discussion at the time, Strengers wrote: ‘astrophysics […] cannot rule out the possibility of a long period of relatively low activity. This could lead to a reduction in warming of up to 0.4 °C (although 0.2 °C is more likely) over the coming 20 to 30 years.’ The past 5 years, therefore, are in keeping with the idea that such a period of relatively low activity is a fact, but the degree to which this reduction will actually continue over the coming years, or for how long it will go on, is still very uncertain.

Relatively high heat absorption by the (deep) oceans

Over 90% of the heat that is added to the climate system, particularly caused by the increase in greenhouse gases, ends up in the oceans. Only a few per cent is stored in the atmosphere. The remainder is absorbed by the land surface and ice sheets (which are therefore steadily melting). Variations in heat absorption can have a large impact on surface temperatures. According to a recent study by England et al., published in December 2013 in Nature, there has been increased heat absorption by the oceans since 2001, which since then has reduced warming by 0.1 to 0.2 °C. The added heat seem to be concentrated largely around the equator in the western part of the Pacific Ocean, at a depth of around 125 to 200 metres, which means it remains ‘hidden’ from the atmosphere. England and his team do not expect this heat storage effect to continue in this way and they project that, at a certain moment, temperatures at the surface level will begin to increase more rapidly. This could happen, for example, due to an El Niño with large amounts of heat being released suddenly, possibly causing temperatures to jump, as happened in 1997–1998 during the so-called super El Niño. Over the past months, a new El Niño seems to be developing. If this continues into 2015, this year may end up being even warmer than the record year of 2014.

A period of cooling due to incidental variations in the climate

The climate knows random variations. Strengers wrote that these may lead to longer periods of no warming or even cooling, even under a steady increase in greenhouse gas concentrations in the atmosphere. During the discussions, Strengers pointed to a study which shows on the basis of climate models that periods of up to 16 years of random cooling or non-warming may occur, even in an overall warming climate. Recent research shows that a combination of random factors likely has led to a reduction in temperature increases over the past 15 years (see the section below, ‘IPCC’s ‘best-estimate’ is that of a warming of 0.2 °C per decade’, for more details). However, this reduction in warming was not high enough for the past 5 years to be cooler than the decade before that.

Lower climate sensitivity than expected

The IPCC – the scientific body that inventories all knowledge on climate change every 5 to 7 years –stated in 2007 in its fourth assessment report (AR4) that climate sensitivity was likely (i.e. with a likelihood of 66%) between 2.0 and 4.5 °C, with a ‘best estimate’ of 3 °C. The fifth assessment report (2013) stated a range of 1.5 to 4.5 °C without giving a ‘best estimate’. The reason for the downward adjustment of the lower limit to 1.5 °C (at which it had been estimated since 1990) originated from a number of studies that pointed to the possibility of a low climate sensitivity. The ‘best estimate’ was not provided “because of a lack of agreement on values across assessed lines of evidence and studies” (i.e. based on all studies up to and including July 2012). All this, however, does not mean that climate sensitivity was ‘less than expected’. In fact, the only thing that can be concluded is that the value of climate sensitivity has become more uncertain.

Further increase in greenhouse gas concentrations in the atmosphere

Greenhouse gas concentrations in the atmosphere have steadily increased over the past 5 years. By late 2014, CO2 concentrations were at 399 ppm (399 molecules of CO2 per million molecules of air). Five years ago this level was 388 ppm. The increase is a direct result from an ever faster increase in CO2 emissions, particularly in countries such as India and China.

IPCC’s ‘best-estimate’ is that of a warming of around 0.2 °C per decade

At the time of IPCC’s fourth assessment report, in 2007, a global warming of 0.2 °C was assumed for the current decade (2010–2019), particularly on the basis of climate model results. As discussed above, the degree of warming according to the UAH series, which is based on satellite measurements, was 0.1 °C over the last 5 years, compared to the mean of the 10 years before that. If this trend continues over the coming 5 years, our current decade will register a warming of around 0.15 °C – slightly less than the ‘best estimate’, but well within the projected range by the IPCC. However, all surface temperature series show a lower degree of warming, between 0.04 and 0.05 °C, over the past 5 years (see the section on ‘What causes the differences between the data series?’). Extrapolation over the 2010–2019 decade shows a total maximum warming of 0.08 °C [typo fixed]. This is in line with the discussion on the ´hiatus´ or the finding that the rate of warming over the past 15 years has been lower than in the 20 years before that, and also lower than the average outcome of many climate models. Note though that there is no significant change in trend from 1998. If climate model calculations take into account the ´random factors´ that cannot be predicted, such as the occurrence of El Niños, solar activity, and volcano eruptions, then models and observations seem much more in agreement.

The chances of overestimating climate sensitivity are smaller than those of underestimation

The IPPC’s fifth assessment report (2013) states that climate sensitivity is likely (66% probability) to be between 1.5 and 4.5 °C. It subsequently states that it is extremely unlikely (less than 5% probability) to be smaller than 1, and very unlikely (less than 10% probability) to be higher than 6.  In other words, very low values are less likely than very high values, which substantiates the above statement.

[Note: hyperlinks added by Bart Verheggen]

Survey confirms scientific consensus on human-caused global warming

August 11, 2014
  • A survey among more than 1800 climate scientists confirms that there is widespread agreement that global warming is predominantly caused by human greenhouse gases.
  • This consensus strengthens with increased expertise, as defined by the number of self-reported articles in the peer-reviewed literature.
  • The main attribution statement in IPCC AR4 may lead to an underestimate of the greenhouse gas contribution to warming, because it implicitly includes the lesser known masking effect of cooling aerosols.
  • Self-reported media exposure is higher for those who are skeptical of a significant human influence on climate.

In 2012, while temporarily based at the Netherlands Environmental Assessment Agency (PBL), my colleagues and I conducted a detailed survey about climate science. More than 1800 international scientists studying various aspects of climate change, including e.g. climate physics, climate impacts and mitigation, responded to the questionnaire. The main results of the survey have now been published in Environmental Science and Technology (doi: 10.1021/es501998e).

Level of consensus regarding attribution

The answers to the survey showed a wide variety of opinions, but it was clear that a large majority of climate scientists agree that anthropogenic greenhouse gases are the dominant cause of global warming. Consistent with other research, we found that the consensus is strongest for scientists with more relevant expertise and for scientists with more peer-reviewed publications. 90% of respondents with more than 10 climate-related peer-reviewed publications (about half of all respondents), agreed that anthropogenic greenhouse gases (GHG) are the dominant driver of recent global warming. This is based on two different questions, of which one was phrased in similar terms as the quintessential attribution statement in IPCC AR4 (stating that more than half of the observed warming since the 1950s is very likely caused by GHG).

Verheggen et al - Figure 1 - GHG contribution to global warming


Figure 1. The more publications the respondents report to have written, the more important they consider the contribution of greenhouse gases to global warming. Responses are shown as a percentage of the number of respondents (N) in each subgroup, segregated according to self-reported number of peer-reviewed publications.

Literature analyses (e.g. Cook et al., 2013; Oreskes et al., 2004) generally find a stronger consensus than opinion surveys such as ours. This is related to the stronger consensus among highly published – and arguably the most expert – climate scientists. The strength of literature surveys lies in the fact that they sample the prime locus of scientific evidence and thus they provide the most direct measure of the consilience of evidence. On the other hand, opinion surveys such as ours can achieve much more specificity about what exactly is agreed upon and where the disagreement lies. As such, these two methods for quantifying scientific consensus are complementary. Our questions possibly set a higher bar for what’s considered the consensus position than some other studies. Furthermore, contrarian viewpoints were likely overrepresented in our study compared with others.

No matter how you slice it, scientists overwhelmingly agree that recent global warming is to a great extent human caused.

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John Christy, Richard McNider and Roy Spencer trying to overturn mainstream science by rewriting history and re-baselining graphs

February 22, 2014

Who are the Flat Earthers?

Before the advent of modern climatology, common wisdom had it that we tiny humans couldn’t possibly influence climate. Modern science shows we can. Yet John Christy and Richard McNider claim the exact opposite in a recent WSJ op-ed, in which they claim that their outdated views on climate somehow make them modern-day Galileo’s (or in their words: Why they are the ones declaring that the earth is round while the vast majority of the climate scientists persist in thinking the earth is flat). They couldn’t be more wrong.

Back then, scientific evidence slowly overturned the religious-cultural notion that the Earth was the centre of the universe. This resulted in a scientific consensus that the Earth revolves around the sun. More recently scientific evidence has started overturning the notion that humans can’t possibly influence something as gigantic as the Earth’s climate. This too has resulted in a scientific consensus  (though a public consensus is still lagging behind). In both cases, the pre-scientific notion was mostly culture-based, as opposed to being evidence-based.

As Jeff Nesbit tweeted: “Being the last scientist to accept established climate science doesn’t make you Galileo.” Quite the opposite indeed.

The Galileo-complex also suggests a rather simplistic view of how science progresses. Rather than a lone skeptic overthrowing a scientific (rather than a cultural) consensus, scientific progress is a usually a gradual process. New evidence has to be reconciled with the existing mountain of evidence; it doesn’t simply replace it. Observing a bird in the air doesn’t disprove gravity. “Skeptics” and their supporters often bring up Galileo as an example of that the scientific consensus can also be wrong, and has been wrong in the past. True enough, though as Carl Sagan said: “they laughed at Galileo, but they also laughed at Bozo the clown”.

Hot spot

Besides their entirely misplaced Galileo-framing, Christy and McNider also make a range of unsupported and/or incorrect statements. One argument deals with the so-called tropical tropospheric hot spot. This refers to the expected stronger warming of the tropical troposphere as compared to the surface. This “hot spot” is independent of the cause of the warming. But what do Christy and McNider write in the WSJ:

(the warming of the deep atmosphere is) the fundamental sign of carbon-dioxide-caused climate change, which is supposedly behind these natural phenomena

But hang on, didn’t Christy admit to the basic science that this hot spot is not specific to a greenhouse effect? Yes, he did (at the ClimateDialogue discussion in which he participated):

“Yes, the hot spot is expected via the traditional view that the lapse rate feedback operates on both short and long time scales. (…) it [the hot spot] is broader than just the enhanced greenhouse effect because any thermal forcing should elicit a response such as the “expected” hot spot.”

So why is he claiming something in the WSJ that he knows to be untrue?

Model-observation comparison

It almost goes without saying that any climate model-observation mismatch can have multiple (non-exclusive) causes (as succinctly summarized at RC):

  1. The observations are in error
  2. The models are in error
  3. The comparison is flawed

But rather than doing a careful analysis of various potential explanations, McNider and Christy, as well as their colleague Roy Spencer, prefer to draw far reaching conclusions based on a particularly flawed comparison: They shift the modelled temperature anomaly upwards to increase the discrepancy with observations by around 50%. Using this tactic, Roy Spencer showed the following figure on his blog recently:

Roy Spencer misleading figure - CMIP5-90-models-global-Tsfc-vs-obs-thru-2013

So what did he do? Jos Hagelaars tried to reproduce the different steps involved. A comparison of annual data, using a 1986-2005 baseline, would look as follows:

Jos Hagelaars - comparison_cmip5_hadcrut4_uah

Spencer used a 5 year running mean instead of annual values, which would (should) look as follows:

Jos Hagelaars - spencers-graph-reconstructed-part-1

The next step is re-baselining the figure to maximize the visual appearance of a discrepancy: Let’s baseline everything to the 1979-1983 average (way too short of a period and chosen very tactically it seems):

Jos Hagelaars - spencers-graph-reconstructed-part-2

Which looks surprisingly similar to Spencer’s trickery-graph. But critiquing Roy Spencer comes at a risk: He may call you a “global warming Nazi”. Those nasty CO2 molecules, that’ll teach them!

Many thanks to Jos Hagelaars for the data analysis and figures.

Is Climate Science falsifiable?

February 17, 2014

Guest post by Hans Custers. Nederlandse versie hier.

A very, ehhrmm… interesting piece on
Variable Variability, Victor Venema’s blog: Interesting what the interesting Judith Curry finds interesting. And I don’t mean interesting in a rhetoric, suggestive way; I mean it is a well-written and well-reasoned article, worth reading.

Victor writes about the meme regularly used by the anti climate science campaign, often supported by some straw man arguments, that the science of human impacts on climate would not be falsifiable. He shows it’s nonsense, by giving some examples of how it could be falsified. Or, more likely, already would have been falsified, if the science would be wrong. Victor’s post inspired me to think of more options to falsify generally accepted viewpoints in climate science. If there are any ‘climate change skeptics’ who want to contribute to real science, they might see this as a challenge. Maybe they can come up with a research proposal, based on one of the options for falsification. Like proper scientists would do.

First, a few more things about falsifiability in general. Bart wrote a concise post about the subject four years ago, explaining that a bird in the sky does not disprove gravity. What looks like a refutation at first, might on second thoughts be based on partial or total misunderstanding of the hypothesis. Natural climate forcings and variations do not exclude human impacts. Therefore, the existence of these natural factors in itself, cannot falsify anthropogenic climate change. A real skeptic is cautious about both scientific evidence and refutations. ‘Climate change skeptics’ like to mention the single black swan, that disproves the hypothesis that all swans are white. Of course that is true, unless that single black swan appears to be found near some oil spill.

Some of the falsifications that I mention later on might be somewhat cheap, or far-fetched. It is not very easy to find options to falsify the science of human impacts on climate. Not because climate scientists don’t respect philosophical principles of science, but simply because there’s such a huge amount of evidence. There are not a lot of findings that would disprove all the evidence at once. A scientific revolution of this magnitude only happens very rarely. Whoever thinks differently, doesn’t understand how science works. (more…)

BBC interview: global warming pause, climate sceptics, long timescales

September 27, 2013

I was interviewed by Matt McGrath from the BBC last week, as were several other Dutch climate spokespeople (including PBL’s senior scientist Arthur Petersen and skeptical science writer/journalist Marcel Crok). Short parts of these interviews have appeared on the web  and on Radio 4 (“The World Tonight”, 26-09). Below I try to provide a bit of context to my quotes.

Both pieces are centred, as is fashionable these days, on the apparent smaller rate of surface warming in the past 15 years. The web piece is entitled “Climate sceptics claim warming pause backs their view”. Of course they claim it does. What sceptics did achieve –credit where credit is due- is to put this so-called “pause” on the agenda of mainstream media, until it got so fashionable that they all feel forced to use it as an anchor for any reporting on climate. But, as Gavin Schmidt is quoted as saying:

focus on a global warming pause over the past 15 years is a “misplaced” distraction that misses the big picture. He said, “The IPCC and the issue of climate change is not about the weather next year or the next five years; it’s about the long-term climate change that we are engendering.”

See also this useful figure from Stefan Rahmstorf, underscoring the silliness of drawing all too strong conclusions from 15-year trends.

giss2012c - Rahmstorf - Global temp with two silly trendlines

Figure showing NASA GISS global average temperatures with trendlines from 1992-2006 (light blue) and 1998-2012 (green) as well as the most recent 30-year trend in red. Naturally, starting in a very cold volcano-influenced or very warm El Nino influenced year will inflate or deflate the trend. (source: Stefan Rahmstorf)

I am quoted in the BBC piece as follows:

Bart Verheggen is an atmospheric scientist and blogger who supports the mainstream view of global warming. He said that sceptics have discouraged an open scientific debate.

“When scientists start to notice that their science is being distorted in public by these people who say they are the champions of the scientific method, that could make mainstream researchers more defensive.

“Scientists probably think twice now about writing things down. They probably think twice about how this could be twisted by contrarians.”

The discussion was about to what extent climate science isn’t open/transparent enough, as contrarians routinely claim. Matt also asked to what extent skeptics actually play a positive role in making science more open/transparent and more self-critical. I said ideally they would. People who are critical usually have a good influence that way. But many climate contrarians don’t just stop at raising partly valid criticism, but go on to distort the science. That has the opposite influence, as scientists noticing this behavior become more careful and more defensive, and(have to) think ahead how their words might get twisted by contrarians. So they may become less open and less frank, and more careful in how they chose their words.

That is the opposite of what contrarians claim they want to achieve, so it’s quite ironic (though entirely logical) that this is the more likely effect of their behavior. It shows quite a lack of self-awareness on their part that they don’t see how their actions and their behavior affect the dynamics of the public debate. For the worse, in most –though not all- cases.

There may also be some lack of self-awareness among the mainstream that they respond in a way that’s not conducive to a long-term open and frank dialogue with society. From an older comment of mine:

If the valid criticisms wouldn’t be packaged in such conspiratorial/accusative/exaggerated (c/a/e) ways, they would be welcomed much more than they currently are. The art that mainstream scientists and their defenders must learn is to take the valid parts of the criticisms and deal with/respond to them, and leave the c/a/e packaging for what it is. That is increasingly difficult because the critics and their supporters will try to keep the c/a/e in (presumably because this packaging is what is most effective at decreasing the scientists’ credibility and sowing doubt). That dynamic needs to be broken. It needs effort from both sides, as difficult and unfair as it sounds.

As I wrote in my earliest (and still rather positive) reflection on the Curry-turn:

There is a tendency of ‘circling the wagons’ within the scientific community, in response to the continuous attacks on the science. Attacks that are mostly based on smear and insinuation rather than solid arguments. (…) I think the ’us-versus-them’ feeling amongst many scientists and their supporters is understandable (as a reaction to the contrarian c/a/e attacks on the science), but counterproductive in the long run.

In the Radio 4 show (at ~33:50 min in; earlier in the downloadable mp3 version), I am saying a few things about the timescale of the problem and of the solution. I brought this up when the discussion was about whether we now have more time to respond to climate change. This is a vastly underappreciated point in the climate discussion:  The climate system will take much longer to cool down than it did to warm up. This is a consequence of how the carbon cycle works. In this context, I said the following:

We’re going somewhere, and if we don’t like where we’re going, we have to turn that wheel in time.  As when you’re on a giant supertanker on the ocean, you can’t say “oh, I’ll wait until I can feel the iceberg with my pinkie and then I’ll turn the wheel”. Then you’re a bit late, so you have to start doing that in time. That’s the other side of the coin. But if you keep banging the drum saying “it’s five to twelve! It’s five to twelve!” doesn’t work either. And that could be counter-effective to engage those who are a bit more skeptical.

Global warming is a problem in slow-motion, hence the “five to twelve” line is not the most useful one to get people on their feet, because if it remains five to twelve for too long, they will tune you out. That’s what happened in the aftermath of COP15 in Copenhagen for example (where the 5-to-12 line was used a lot, and not much has changed in the years since). The supertanker analogy is more appropriate I find, since that makes clear that even though the problematic situation that’s on your path isn’t in close proximity yet, it is necessary to change course, if you wish to avoid it.

Supertanker

Comment on EER interview with Fritz Vahrenholt

June 11, 2012

Also published in European Energy Review (EER).

Greenhouse gases are responsible for warming, not the sun

Scientists working on climate on a daily basis must have been rather astonished by the interview with Professor Fritz Vahrenholt (European Energy Review, May 2, free registration required). Vahrenholt, chief of RWE Innogy, self-proclaimed climate expert and author of the book Die Kalte Sonne (The Cold Sun), claims that “the contribution of CO2 to global warming is being exaggerated”. These claims, however, do not stand up to scientific scrutiny. We assess his ideas in the light of the scientific literature on the role of the sun versus other climate forcing factors. The dominant influence of greenhouse gases follows not only from their basic physical properties, but also from their “fingerprint” in the observed warming. The sun, in contrast, has not exhibited any warming trend over the past 50 years. The sun is thus not responsible for the warming seen during this period. Greenhouse gases in all likelihood are.

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Confusing the net cloud effect with a cloud feedback: Very different beasts

September 20, 2011

I stumbled upon a new post at WUWT today:

New peer reviewed paper: clouds have large negative-feedback cooling effect on Earth’s radiation budget

Note that Anthony has since changed the title to leave out the word “feedback”, which was the source of his confusion. It starts out as follows:

Oh dear, now we have three peer reviewed papers (Lindzen and Choi, Spencer and Braswell, and now Richard P. Allan) based on observations that show a net negative feedback for clouds, and a strong one at that. (…) The key paragraph from the new paper:

…the cloud radiative cooling effect through reflection of short wave radiation is found to dominate over the long wave heating effect, resulting in a net cooling of the climate system of −21 Wm−2.

The attentive reader will immediately spot the problem here. Watts is confusing two issues:

– the net radiative effect of clouds on climate (i.e. in comparison with having no clouds at all)

– the net feedback of clouds in response to a change in climate

The paper addresses the first, whereas Anthony interpreted it as if it addresses the second.

These are two distinctly different issues. The latter (clouds as feedback) is about how cloud cover and properties might change in response to a warming or cooling of the climate: Will the net cloud radiative effect (i.e. the former) become more or less negative.

The net radiative effect of clouds on Earth’ climate has long been known to be negative (i.e. cooling). See e.g this quote from the paper:

The overall global net cloud radiative effect is one of cooling as documented previously (Ramanathan et al., 1989).

That can be verified in any textbook on the subject and most introductions of papers on this topic. Or in my introductory post on aerosols, clouds and climate.

I pointed this error out in the thread, as did more than a few others after me (including Roy Spencer). Only after the author of the paper, Richard Allan, came in to say that this post mis-interpreted the paper, did Anthony change the title and added an update. The mistaken interpretations are still in the body of the text though.

Richard Allan wrote to me in email (reproduced with permission):

I was surprised that this paper was linked to cloud feedback since, as you mention, it attempts to quantify the well known influence of cloud on Earth’s radiation budget (at the top of the atmosphere, at the surface and within the atmosphere and also during day and night) and does not attempt to diagnose cloud feedback.

Watts goes on to say (bold in original):

The cooling effect is found to be -21 Watts per meter squared, more than 17 times the posited warming effect from a doubling of CO2 concentrations which is calculated to be ~ 1.2 Watts per meter squared.

He’s comparing apples and oranges. The 21 W/m2 is the top of the atmosphere (TOA) cloud forcing in reference to having no clouds at all (see table 1 in the paper); the 1.2 W/m2 is the surface forcing due to a doubling in CO2 concentrations. The TOA forcing of a doubling in CO2 is closer to 4 W/m2. But that’s not the “zero” point. The total greenhouse effect (due to water vapor, clouds, CO2 and other GHG) is about 150 W/m2.                                                                                                                   

In other words, this paper falls squarely within the mainstream; it further quantifies a (previously known) net cooling effect of clouds on the Earth’ climate; it does not quantify how clouds may change in response to warmer climate (cloud feedback), though it does provide a carrot stick in saying that these types of analyses are important “in assessing cloud climate feedbacks which contribute substantially to uncertainty in climate prediction.”. That may very well be, but it hasn’t been done in this paper (as confirmed by its author). 

Judging by the comments, many at WUWT took this, in combination with the whopping -21 W/m2, to mean that they discovered a gigantic negative feedback. Nope.

Tallbloke (from Lisbon fame) still insists that

if [cloud forcing] becomes slightly less negative, it’s still very negative, and overwhelms the effect of changes in co2.

… being very confused. Comments vary over a very wide range though. Many are confused (e.g. stating that as specific humidity goes up in a warmer world, so should cloud cover, whereas cloud formation depends on relative humidity rather than on specific humidity), there’s lots of laughing-at-the-scientists going on, but there are also sensible comments that either offer insight or good questions.

Mosher makes the following observation:

it is also fascinating because of what we dont see. usually you will see a whole crew of commeters pounce on the word “model”. This time they didnt.

They didnt because they thought the paper supported spencer. But it was on an entirely different topic. That misunderstanding kinda silenced the usual “models are bad” crew.

Spencer and Braswell fundamentally flawed, journal editor resigns

September 2, 2011

Wolfgang Wagner, editor-in-chief of the journal Remote Sensing, resigns over the publication of a fundamentally flawed paper:

[peer review is] supposed to be able to identify fundamental methodological errors or false claims. (…) the paper by Spencer and Braswell that was recently published in Remote Sensing is most likely problematic in both aspects and should therefore not have been published.

Peter Gleick has a good rundown of the story.

Wagner points out that minority views are and should be welcomed in the scientific literature. But he adds that that does not mean that long refuted arguments should be able to keep being published:

The problem is that comparable studies published by other authors have already been refuted in open discussions and to some extend also in the literature, a fact which was ignored by Spencer and Braswell in their paper and, unfortunately, not picked up by the reviewers. In other words, the problem I see with the paper by Spencer and Braswell is not that it declared a minority view (which was later unfortunately much exaggerated by the public media) but that it essentially ignored the scientific arguments of its opponents. This latter point was missed in the review process, explaining why I perceive this paper to be fundamentally flawed and therefore wrongly accepted by the journal.

What Stoat reads this to mean is that

Yes, novel and interesting challenges to the established view should be published – perhaps even get given a slightly easier ride, if they are novel. But No: just saying the same old thing again isn’t any good.

Quite predictably, Roy “Conspiracy” Spencer is complaining about the IPCC gatekeepers trying to silence dissenting geniuses like him.

Update: Dan Satterfield observes that

They [“skeptical” papers such as Spencer’s] are not published to further the science, but as a piece of meat to those who find the science very incompatible with their world view.

Dutch translation of this post on my NL klimaatblog.

Update 2: Robert Grumbine reminds us of how Spencer sees his own role:

“I view my job a little like a legislator, supported by the taxpayer, to protect the interests of the taxpayer and to minimize the role of government.”

In the comments, Bob Brand makes several astute observations on the course of events and on Wagner’s apology to Trenberth (and the role of cultural differences therein). Re the apology, I see Wagner’s resignation as an apology to the scientific community and don’t find personal apologies to Trenberth necessary, though BB provides some rationale for this.

William Connolley provides some insights:

people are using short-cuts to try to evaluate who is correct. This is inevitable; if we restricted discussion to those who understood the issues, there would be far less debate.

(…) the obvious explanation for Wagner’s explanation, the one he actually gave: personal morality. He doesn’t want to be associated with this paper, and has used the only means available to free himself.

I would sum up Wagner’s reasons for resigning as follows:

  • the lack of considering (previously published) contradictory evidence.
  • the (in Wagner’s words) problematic issues w.r.t. “fundamental methodological errors or false claims.”
  • Spencer’s exaggerations and over-interpretations of his results (which made Wagner feel that he had been taken for a ride).

Scott Denning’s smashing presentation at Heartland climate conference ICCC6

August 13, 2011

Listen to Scott Denning’s sharp and to-the-point presentation, which he gave at Heartland’s climate conference, here. It’s worth the full 16 minutes of it. He rocks. Alternatively, read this little recap:

Denning attended the Heartland conference for the second year in a row and it seems like he’s outdone himself by giving an even better and sharper presentation than last years (which was excellent as well).

He emphasized some very important things:

– The big picture is what matters; details do not (at least in terms of policy relevance; for science nerds of course it’s different)

– Part of that big picture is that, whatever the sensitivity, a 400% increase in CO2 is going to make a big difference to the climate, because of the simple fact that adding heat warms things up.

– He offered a big challenge to the (strongly contrarian and libertarian) audience: Propose and advocate for effective solutions, otherwise others will. Policy will be enacted anyway. His challenge got particularly strong when he said “do you want Greenpeace to dictate the policy? (…) Are you cowards?”

(more…)


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