John Cook, proprietor of the grossly mis-named website, SkepticalScience, published a study in which Cook claims, “A new survey of over 12,000 peer-reviewed climate science papers by our citizen science team at Skeptical Science has found a 97% consensus among papers taking a position on the cause of global warming in the peer-reviewed literature that humans are responsible.”  That’s the headline picked up by the gullible press.

Unlike what would be implied by the name, SkepticalScience is a proponent of catastrophic anthropogenic global warming (AGW).

The study involved reading the abstracts from 11,944 papers which contained the words “global warming” or “global climate change” published in the period 1991-2011.  The “team” rated these papers according to seven criteria judging their support for AGW, see definitions of the categories in table 2 of Cook’s published paper here.

The actual findings of the survey, in Cook’s own words: “We find that 66.4% of abstracts expressed no position on AGW, 32.6% endorsed AGW, 0.7% rejected AGW and 0.3% were uncertain about the cause of global warming.”  So how do you get a 97% consensus out of that?

That question has been discussed on many blogs.  The best explanation I’ve found is one by Dutch researcher Marcel Crok, “Cook’s survey not only meaningless but also misleading.“

Here are some excerpts [I made minor edits of spelling]:

Cook et al. selected around 12,000 scientific abstracts that contained the words “global warming” or “global climate change” published in the period 1991-2011. With a large group of volunteers they then rated the papers using 7 categories. Around 8000 of the abstracts (2/3) take no clear position on Anthropogenic Global Warming (AGW). Of the remaining ~4000 abstracts more than 97% “endorse AGW” according to the paper. Only a tiny amount (78 papers) “reject AGW”. Hence they claim again that there is a consensus, that the debate is over and also that there is a gap between scientists and the public.

Now here comes the misleading part. If an abstract/paper “endorses AGW”…[this means that] change is real, man-made and dangerous.

To the credit of the researchers they made all their results available in a searchable database. Their rating system is online as well. There are 7 levels of endorsement, going from quantified endorsement of AGW all the way down to a quantified rejection of AGW. Seems fair enough. But here  is the issue. Only the first category can be regarded as a real or strong endorsement of AGW. Here is the description of category 1:

1. Explicit Endorsement of AGW with quantification

1.1 Mention that human activity is a dominant influence or has caused most of recent climate change (>50%).

1.2 Endorsing the IPCC without explicitly quantifying doesn’t count as explicit endorsement – that would be implicit.

Now specifically look at 1.1. This comes close to the iconic statement from the IPCC AR4 report which said that “Most of the observed increase in global average temperatures since the mid-20th century is very likely due to the observed increase in anthropogenic greenhouse gas concentrations.” Now if 97% of the abstracts would repeat in slightly varying terms this major conclusion, then at least the conclusion of the survey would be more or less fair. However the survey doesn’t come even close.

Brandon Shollenberger, who is guest blogger at The Blackboard, was the first who reported that actually only 65 papers have been rated “category 1.” Yes that’s right, only 65 abstracts clearly “mention that human activity is a dominant influence or has caused most of recent climate change (>50%);” 65 on a total of 12,000 is 0.5%. So a completely fair conclusion from their survey is that only 1 in 200 abstracts explicitly mentioned that humans are dominating climate. If you ignore the 8000 papers that were labeled category 4 (neutral, meaning having no position on AGW) the 65 would be 1.6%.  The paper reported that only 78 papers (1.9% if you ignore the 8000 neutral abstracts) rejected AGW.

Now where is the 97% endorsement of AGW coming from? What the authors did is to add up the numbers of categories 1 to 3 and of the categories 5 to 7 which I show below:

Category 1: 65 [Explicit endorsement with quantification]

Category 2: 934 [Explicit endorsement without quantification]

Category 3: 2933 [Implicit endorsement]

Category 4: 8261 [No position or uncertain]

Category 5: 53 [Implicit rejection]

Category 6: 15 [Explicit rejection without quantification]

Category 7: 10 [Explicit rejection with quantification]

Total:         12271

As you can see the 78 “rejection of AGW” abstracts are the added number of categories 5-7. Categories 1-3 together add up to 3932 papers. This 3932 divided by 4010 (the total of categories 1-3 + 5-7) gives their impressive 97% …However of these 3932 abstracts 2933 (75%) fall in category 3. Now how strong is the endorsement of AGW in this category? Here is the description:

3. Implicit Endorsement of AGW

3.1 Mitigation papers that examine GHG emission reduction or carbon sequestration, linking it to climate change.

3.2 Climate modeling papers that talks about emission scenarios and subsequent warming or other climate impacts from increased CO2 in the abstract implicitly endorse that GHGs cause warming.

3.3 Paleoclimate papers that link CO2 to climate change.

3.4 Papers about climate policy (specifically mitigation of GHG emissions) unless they restrict their focus to non-GHG issues like CFC emissions in which case neutral.

3.5 Modeling of increased CO2 effect on regional temperature – not explicitly saying global warming but implying warming from CO2.

3.6 Endorsement of IPCC findings is usually an implicit endorsement.

I like 3.2: “endorse that GHG’s cause warming.” I also strongly agree with this part of 3.5: “implying warming from CO2?. The meaningless result of their whole exercise is that 75% of the abstracts that say something about AGW at all “link CO2 to climate change” or “imply warming from CO2. [This does not necessarily mean endorsement or consensus.]

If we just say “Humans cause some global warming,” we could be supporting a value 20% or 90%. Despite being able to support either position, we’d land in the top categories. That means the results will automatically be skewed toward the top.

Australian science reporter Jo Nova has some other choice comments in her post, “Cook’s fallacy ‘97% consensus’ study is a marketing ploy some journalists will fall for.”

“What does a study of 20 years of abstracts tell us about the global climate? Nothing. But it says quite a lot about the way government funding influences the scientific process.”

Jo Nova cuts to the chase with the following points (which are further explained in her post):

1. Thousands of papers support man-made climate change, but not one found the evidence that matters.

2. Cook’s study shows 66% of papers didn’t endorse man-made global warming. Cook calls this “an overwhelming consensus”.

3. Cook’s method is a logical fallacy: Argument from Authority. This is not science, it’s PR.

4. The number of papers is a proxy for funding.

5. Most of these consensus papers assume the theory is correct but never checked. They are irrelevant.

Read her post for seven more points.

All of this is about consensus, as if consensus is equated with truth, but it isn’t, see my post “On Consensus in Science.”  In that post I show the origins of previous claims of consensus and show several examples of famous errors of consensus.

“It does not matter who you are, or how smart you are, or what title you have, or how many of you there are, and certainly not how many papers your side has published, if your prediction is wrong then your hypothesis is wrong. Period.” -Richard Feynman

“I regard consensus science as an extremely pernicious development that ought to be stopped cold in its tracks. Historically, the claim of consensus has been the first refuge of scoundrels; it is a way to avoid debate by claiming that the matter is already settled. Whenever you hear the consensus of scientists agrees on something or other, reach for your wallet, because you’re being had.” -Michael Crichton.

UPDATE: Cook’s 97% consensus study falsely classifies scientists’ papers according to the scientists that published them.

Atmospheric concentration of carbon dioxide temporarily topped the 400ppm mark for a few hours at the Mauna Loa observatory in Hawaii precipitating a media frenzy. Typical of the hype is this story from the New York Times which begins: “The level of the most important heat-trapping gas in the atmosphere, carbon dioxide, has passed a long-feared milestone, scientists reported Friday, reaching a concentration not seen on the earth for millions of years.” There are two errors of fact in that sentence: 1) water vapor is the most important heat-trapping gas, and 2) CO₂ concentrations above 400ppm were reported from the 1820s and from the 1940s.

Here is the graph showing the “monumental” event from Mauna Loa:

And here is a graph showing analyses from previous research on atmospheric carbon dioxide:

Note that both the modern measurements at Mauna Loa and the older measurements are measuring point sources which may or may not reflect global concentrations. The older chemical methods reported by Beck used a chemical analysis of air captured in flasks. Lest you think that’s too old fashioned, note that NOAA still uses that method to check the Mauna Loa data. “NOAA’s Earth Science Research Laboratory program also measures CO₂ in weekly flask samples taken at over 60 remote locations around the world.” (See link below)

The Mauna Loa observatory sits on the flank of an active volcano which “emits variable amounts of carbon dioxide (CO₂) and sulfur dioxide (SO₂) from fissures at the summit.” NASA explains how scientists attempt to distinguish between carbon dioxide from volcanic emissions and overall atmospheric concentration here.

There is another fly in the ointment reported by Scripps Institution of Oceanography:

“Starting around May 1, we began experiencing intermittent difficulties with the computer used to control the Scripps CO₂ analyzer at the Mauna Loa Observatory. This led to delays in providing daily values and also some data gaps. Although such difficulties are not uncommon and rarely lead to significant long-term data loss, we have decided to switch over to reporting daily values from second Scripps instrument, operated in parallel at Mauna Loa…”

Whether or not the atmospheric carbon dioxide concentration has topped a “long-feared milestone” is irrelevant. Carbon dioxide rises as a result of increasing temperature which causes carbon dioxide to exsolve from the oceans and also rises from our increasing use of fossil fuels. For most of Earth’s history carbon dioxide has been well above 1,000ppm and Earth not only survived but life was robust and verdant.

Instead of fearing this artificial milestone, we should celebrate it and try to increase the atmospheric carbon dioxide concentration. For the reason see: A Modest Proposal: Triple Your Carbon Footprint.

See also:

Which comes first, rise in global CO₂ or rise in global temperature?

The Eocene climatic optimum and paradise lost

A new paper by Dr. Nicola Scafetta of Duke University examines the relationship of natural, solar-driven ocean oscillations such as the Pacific Decadal Oscillation (PDO), Atlantic Multidecadal Oscillation (AMO), and the North Atlantic Oscillation (NAO) to the changes in rate of sea level rise. He finds no correlation with atmospheric carbon dioxide or temperature.

Before I get into the Scafetta paper, here is some background.

Measuring sea level is more complicated than pounding a stake into a beach. Ideally, global sea level would be a rotating oblate ellipsoid of polar radius of 6365.752 km and equatorial radius of 6378.137 km in absence of any other forces. Gravity distorts this ideal shape to make it lumpy.

There are daily and seasonal variations, and storm surges in addition to the oscillations mentioned above. There are tectonic events: is the ocean rising or is the land sinking? Also, extraction of groundwater near coasts may cause the land to sink and present an apparent rise in sea level. All these confounding factors can produce a local rate of sea level change very different from global rate of change.

Since the end of the last glacial epoch, sea level has risen 120 meters (393 feet), about one meter per century. Sea level is still rising at the rate of 1- to 3mm per year, according to NOAA, about the thickness of one or two pennies.

As you can see from the figure, the rate of sea level rise has changed on broad time scales. Scafetta has found patterns of acceleration and deceleration of rise at much smaller time scales.

Scafetta studied six long-term tidal gauge records sited to represent all of the world’s oceans. He found the rate of sea level rise “…to be characterized by significant oscillations at the decadal and multidecadal scales up to about 110-year intervals. Within these scales both positive and negative accelerations are found if a record is sufficiently long. This result suggests that acceleration patterns in tide gauge records are mostly driven by the natural oscillations of the climate system. The volatility of the acceleration increases drastically at smaller scales such as at the bi-decadal ones.”

“Tide gauge accelerations oscillate significantly from positive to negative values mostly following the PDO, AMO and NAO oscillations. In particular, the influence of a large quasi 60–70 year natural oscillation is clearly demonstrated in these records.”

A conclusion from this paper has implications for climate model predictions: “at scales shorter than 100-years, the measured tide gauge accelerations are strongly driven by the natural oscillations of the climate system (e.g. PDO, AMO and NAO). At the smaller scales (e.g. at the decadal and bi-decadal scale) they are characterized by a large volatility due to significant decadal and bi-decadal climatic oscillations. Therefore, accelerations, as well as linear rates evaluated using a few decades of data (e.g. during the last 20-60 years) cannot be used for constructing reliable long-range projections of sea-level for the twenty first century.”

The cyclical nature of the rate of sea level rise, and its quite variable accelerations and decelerations at different time scales may explain why different researchers get different rate values. So, scary stories saying we are doomed because of acceleration in the rate of sea level rise, such as the ‘science fiction” stories linked below, should be taken with a grain of salt.

Reference: Scafetta, N., 2013, Multi-scale dynamical analysis (MSDA) of sea level records versus PDO, AMO, and NAO indexes, Climate Dynamics, DOI 10.1007/s00382-013-1771-3.

See the full paper here.

See also:

Science Fiction from the University of Arizona?

More science fiction from the University of Arizona

University of Arizona dances with sea level

Sea Level Rising?

Sea Level Rise in the South Pacific: None

Sea Level Rise Declining says EU

Obama parts the waters, sea level drops

Size matters in sea level studies

Sea level rising fast along American East Coast – or not