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Wednesday, 3 May 2017

Online trolls and climate science: The latest attempted lie by Anthony Watts



I posted on Twitter last night that Kevin Grandia in 2009 had referred to the folks posting on Watts Up With That as a 'bunch of online trolls with precious little science'. Well, that isn't the remark but it's pretty close. Grandia was posting in The Huffington Post and he was absolutely right about them in my view, judging from my own experience.

I could carry on countering the comments on Willis Eschenbach's piece, but it's actually pretty monotonous really, so time to move on. Well, in a fashion.

The comments, or some of them, are fairly good examples of the standard myths put out by deniers, so its worth countering them in a way, but really only as 'case studies' and opportunities to present the truth of what's going on with climate change. On a wider scale, it's worth watching WUWT generally, as more blogs appear on there every day, and of course these lies have to be countered. However, there are other things to do as well. For that reason, it's probably best, now, to focus on the headline blogs on WUWT and other stuff that makes it out of the comment zone and into the wider online discussion arena.

The latest WUWT lie by Anthony Watts states that NOAA tide gauge data shows no sea level rise acceleration. It mentions the IPCC AR5 WG1 (the IPCC 5th Assessment Report 2013), and it is worth taking a look at that first. The Summary for Policymakers for AR5 is here. Some of the conclusions it draws are as follows:
  • The atmosphere and ocean have warmed, the amounts of snow and ice have diminished, sea level has risen and the concentrations of greenhouse gases have increased.
  • The globally averaged combined land and ocean surface temperature data, as calculated by a linear trend, show a warmong of 0.85 (0.65 degrees C to 1.06 degrees C) over the period 1880 to 2012, when multiple independent produced datasets exist. The total increase between the average of the 1850-1900 period and the 2003-2012 period is 0.78 (0.72 to 0.85 degrees C), based on the single longest dataset available.
  • It is virtually certain that the troposphere has warmed since the mid-20th century.
  • It is very likely that the number of cold days and nights has decreased and the number of warm days and nights has increased on the global scale since 1950.
  • On a global scale, the ocean warming is largest near the surface, and the upper 75 metres warmed by 0.11 (0.09 to 0.13 degrees C) per decade over the period 1971 to 2010. 
  • Proxy and instrumental sea level data indicate a transition in the late 19th to the early 20th century from relatively low mean rates of rise over the previous two millennia to higher rates of rise (high confidence). It is likely that the rate of global mean sea level rise has continued to increase since the early 20th century.
The WUWT blog piece cites one of the AR5 comments:

"It is very likely that there is a substantial anthropogenic contribution to the global mean sea level rise since the 1970s. This is based on the high confidence in an anthropogenic influence on the two largest contributions to sea level rise, that is thermal expansion and glacier mass loss"

Here's the WUWT cruncher:

"NOAA tide gauge coastal sea level rise data measurements encompassing the 46 year period from 1970 through 2016 do not support and in fact clearly contradict the UN IPCC AR5 WG1 conclusion regarding supposed man made contributions to increasing rates of sea level rise since the early 1970s."

There is no explanation of this statement at all, and I suspect it's based on cherrypicking of the data. Meanwhile, we should turn to this NOAA sea level rising fact sheet:

"Yes, there is strong evidence that global sea level gradually rose in the 20th century and is currently rising at an increased rate, after a period of little change between AD 0 and AD 1900. Sea level is projected to rise at an even greater rate in this century. The two major causes of global sea level rise are thermal expansion of the oceans (water expands as it warms) and the loss of land-based ice due to increased melting"


The NOAA fact sheet doesn't actually say that the cause of the expansion of the oceans from warming and the increased melting is due to human activity. However, the mention of increased melting of ice, along with the other NOAA data correlates with the data available elsewhere suggesting that it is human activity that is causing the warming. This means that Watts needs to support its statement that NOAA data does not support man-made warming. He doesn't.

Elsewhere, the NOAA site features a paper by Bruce B. Parker Marine Technology Society Journal, Vol. 25, No. 4, 1992. This is fairly dated now but it states that:

"The present temperature and salinity profile data base appears to be inadequate to produce reliable, long series of steric heights to look at this question"

So does NOAA believe that sea level rise is due to man-made climate change?

Yes. There is a video on this NOAA Ocean Service website, produced by NASA and NOAA, that explains this perfectly.

What Anthony Watts is doing is that he's taking advantage of the NOAA's apparent reluctance to link data concerning sea level rise with man-made global warming to drive doubt into the discussion.

Next, Watts goes on to talk about semi-empirical models (SEMs), citing a passage in AR5:

"Many semi-empirical model projections of global mean sea level rise are higher than process-based model projections (up to about twice as large), but there is no consensus in the scientific community about their reliability and there is thus low confidence in their projections"

Watts uses this problem with SEMs to cast doubt on a report by the California Ocean Science Trust, reported by The Mercury News, which suggests that sea level rise off California could rise by 10 feet over sea level rise.

On this discussion of sea level rise, NASA says this:

"Projections of global sea level rise by 2100, the year upon which climate modelers typically focus, vary widely depending on modeling methods and on assumptions—the rate of increase in greenhouse gas emissions, for example, and especially how ice sheets will respond to warming air and ocean water."

And:

"SEMs [Rahmstorf et al., 2012 and references therein] take a simple approach—a kind of shortcut—to simulating future sea level rise. Instead of trying to model the processes underlying sea level change, these models rely on sea-level changes observed in previous decades and their relationship to global temperature. Then they apply that same relationship to the century to come. The resulting projections tend to be significantly higher than those derived from process-based modeling."

And:

"An illustrative example can be found in a recent study contrasting the projections of process-based and semi-empirical models [Perrette et al., 2013]. Global mean sea level rise from major sources—thermal expansion, glaciers, and the Greenland and Antarctic ice sheets—total 0.42 meters by 2100 in the process based RCP 6.0 model, considered a mid-range, standard-type emission scenario. But updated with the semi-empirical approach, the same model yields a total of 0.86 meters, more than twice the process-based value." 

A paper by John C. Moore et al (2015) says this in its abstract:

"We review the two main approaches to estimating sea level rise over the coming century: physically plausible models of reduced complexity that exploit statistical relationships between sea level and climate forcing, and more complex physics-based models of the separate elements of the sea level budget. Previously, estimates of future sea level rise from semiempirical models were considerably larger than those from process-based models. However, we show that the most recent estimates of sea level rise by 2100 using both methods have converged..."

Stefan Rahmstorf (2007) in Science explains the situation thus:

"...our capability for calculating future sea-level changes in response to a given surface warming scenario with present physics-based models is very limited, and models are not able to fully reproduce the sea-level rise of recent decades. Rates of sea-level rise calculated with climate and ice sheet models are generally lower than observed rates. Since 1990, observed sea level has followed the uppermost uncertainty limit of the Intergovernmental Panel on Climate Change (IPCC) Third Assessment Report (TAR), which was constructed by assuming the highest emission scenario combined with the highest climate sensitivity and adding an ad hoc amount of sea-level rise for “ice sheet uncertainty

While process-based physical models of sea-level rise are not yet mature, semi-empirical models can provide a pragmatic alternative to estimate the sea-level response. This is also the approach taken for predicting tides along coasts (for example, the well-known tide tables), where the driver (tidal forces) is known, but the calculation of the sea-level response from first principles is so complex that semi-empirical relationships perform better. Likewise, with current and future sea-level rise, the driver is known [global warming (1)], but the computation of the link between the driver and the response from first principles remains elusive. "

So, Watts is using the uncertainty among scientists regarding whether or not SEMs can be relied upon to predict future sea-level rise to cast doubt on scientific reports focusing on sea level rise and their inevitable coverage by the media.

However, Rahmsdorf makes it clear that this is basically detail, that the issue is "computation of the link between the driver and the response". The larger, overriding, conclusion that global warming is causing sea level rise is already known and accepted.

Except by climate change deniers that is....



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