A Worry of Climate Change Scientists

A friend of mine, JP, started all of this when writing:

If you were to ask me 2 years ago what my key understandings were about climate change, I would have said the following:

Sea ice is rapidly shrinking (summer arctic sea ice to be gone by 2015)

Sea levels are rising and accelerating

Polar bear populations are under stress (have increased in the last 20 years)

The levels of glacial retreat around the world are unprecedented (similar retreats have been seen in the last century)

97% of scientists agree that global warming is real and an urgent problem

Any scientist who is skeptical about the claims made about climate change is a "denier" and is funded by oil/resource companies

We are seeing an increase in extreme weather events (they are actually getting less common)

Climate models are accurate in their predictions 

Every one of those things is either totally false, or a largely exaggerated claim.

This is the fifth in a series based on my response, which itself was split over a few emails.  The first was Ice Extent Challenge (in which I provided a little more context about JP) and was followed by Sea Levels Rising, Polar Bears and Climate Change and Glacial Retreat.  Some of the issues may also be touched on in a series of articles on the nature of climate denialism.  Please also note the caveat.

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JP’s Claim: The statement “97% of scientists agree that global warming is real and an urgent problem” is either totally false or largely exaggerated

First, I should point out that the title of this post is quite misleading.  By “worry” in this context, I am introducing a new collective noun (like a “murder” of crows, or a “parliament” of owls, or an “embarrassment of climate deniers”), when you get sufficiently many climate change scientists grouped together and agreeing on something, then you have a “worry”.  I suggest that 97% sounds like a nice round number.

Second, it is well known that 98.23% of ridiculously precise statistics are made up (more on that here).  JP seems to have taken the 97% figure from NASA, who got their figure from Environmental Research Letters (albeit via an intermediate paper, also at Environmental Research Letters).  It should be noted that this is specifically related to publishing climatologists.  If one includes non-publishing climatologists, the figures drop markedly – although there is a notable increase in certainty over time even on the part of non-publishing climatologists over time – 66% in 1991 (Gallup – AMS/AGU members) and 87% in 2015 (Pew – AAAS members).  There’s an interesting chart that relates:

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The 97% figure is of great interest to denialists such as Joanne Nova who called for the paper to be retracted (and it’s quite enlightening to read her commenters).  What she seems to have overlooked is that the paper (by John Cook among others) clearly indicates that the work was “conceived as a 'citizen science' project by volunteers contributing to the Skeptical Science website”.  There’s no hiding the weaknesses of the methodology and it’s hardly their fault that media may have picked up the conclusions and presented them as if they represented stone cold fact rather than a rough indication of where the consensus lies.

She ignores that an NAS research article in 2010 resulted in very similar findings.  She also ignores that around 200 scientific organisations world-wide concur with the consensus on anthropogenic climate change (198 are listed, but it’s unlikely that this list put together by the Californian Governor’s Office of Planning and Research is entirely comprehensive).

While we can quibble about the precise figure, it is clear that a large percentage of scientific organisations and scientists, particularly those working in related areas, agree that there is an element of human influence in climate change.  But even if the figure of 97% was adjusted down to say 80% or 70%, this would not change the fact of climate change.  Scientists who argue the anthropogenic climate change case do not rely on authority or numbers of people who agree with them.  They use evidence, both in the form of measurements over many decades and in the form of modelling which relies on physical understanding of the climate (more on that in a later post).

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In this instance, JP’s position – as stated – is correct.  It is an exaggeration to say that “97% of scientists agree that global warming is real and an urgent problem”, but both the primary source (Quantifying the consensus on anthropogenic global warming in the scientific literature) and secondary sources (Environmental Research Letters and NASA's page Scientific Consensus: Earth's Climate is Warming) make it clear that this figure refers to “actively publishing climate scientists”, not scientists in general.  Additionally, the consensus in question is with respect to the notion that “humans are causing global warming”, not that “global warming is real and an urgent problem”.  As far as I can tell, there simply isn’t any data on the latter.

Is JP’s position relevant though?  Not really, on-going rebuttals of the 97% figure by denialists are little more than a distraction.

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This issue is explored in far greater detail at Skeptical Science.

Glacial Addition

This is a follow on to Glacial Retreat, as I stumbled on another glacier related email while trying to find a response from JP.  For context, JP had effectively claimed that glaciers around the globe aren’t retreating at an unprecedented rate.  I responded, and he responded with this (tidied up a little):

In the past perhaps going back to the early 1980s, climate scientists in North America (NASA and NOAA) were publishing charts of global temperatures.  These showed rapid warming in the early part of the century perhaps to 1940 followed by rapid cooling perhaps to about 1975.  These published charts were accompanied by press articles at the time that talked about massive changes in glacial and arctic ice. These press reports were consistent with the reported NASA and NOAA data.  Glaciers were catastrophically melting and then advancing. Arctic ice was massively retreating, then advancing. The cooling from 1945 to 1975 was so marked and the glacial and arctic ice advance so significant that leading climate scientists at the time were speculating about a coming ice age. 

What follows is edited from my response to the highlighted claim.  Before I get into it however, a few clarifying comments regarding the surrounding text.

NOAA was founded in October 1970.  Glaciers have been monitored in a coordinated fashion by the US since 1957 when the World Data Center for Glaciology (WDC) was established.  The WDC was transferred from the US Geological Survey to NOAA in 1976.  NSIDC was created as a separate entity in 1982, and was eventually supported by not only NOAA but also NASA from the 1990s.  NASA is more interested in sea ice than glaciers per se, but even so there was no continuous monitoring of sea ice until 1979.  There was some imagery taken prior to that, by satellites that were not dedicated to the task.  The point here is that there are serious issues associated with claiming anything related to NASA and NOAA records of sea ice and glaciers prior to 1975.

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The Quaternary Science Reviews article  Glacier fluctuations during the past 2000 years  is packed with interesting data and also some telling figures (although they are occasionally quite difficult to read).  Here are two that stand out for me, both from page 16:

The rubric below says:

Fig. 4. Glacial extent: yellow – glacier(s) smaller than now (end of 20th-early 21st centuries); pale yellow – glacier(s) smaller than maximum extent, but size is generally not well known (included here only if this status is clearly indicated in the original publications, mostly based on the ages of wood incorporated into till or overrun by glaciers); light green – glaciers present in the watersheds (only for lake-sediment records); light blue – glacier(s) advancing or expanded; dark blue – glacier(s) close to or at their maximum extent of the past 2 ka. Although a few glaciers experienced small-scale, intermittent advances during recent decades they were too minor to represent on this summary diagram. The empty cells indicate the absence of information on the glacier status. The descriptions of all series are listed in SM Table 1. The sequence of the series corresponds to the sequence of the records in the SM Table 1. Temperature reconstructions gridded at 50 years (50 year mean) (PAGES 2k Consortium, 2013).

and

From these people at least there is no evidence of glaciers “catastrophic melting and then advancing”.  Admittedly the time scale is not the most useful for looking at the last century, but what seems to be happening is that in the first half of the last century, either glaciers were close to (or at) their maximum extent or they were advancing and the number of advances has plummeted since the beginning of the 1900s which was already a decrease on where things were at the beginning of the 1800s – but it’s not zero unless, possibly, you were to exclude Canada and the USA.

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My apologies to anyone who thought that “glacial addition” meant something like “glacial advance”.