Getting rid of the spurious blips - another look at global sea surface temperatures

Kevin Cowtan | Source: U York

Once again, Kevin Cowtan has brought his skills to climate science, working with Robert Rohde and Zeke Hausfather. They decided to explore those pesky ups and downs in the temperature record, which a lot of people (scientists mostly) have expressed concerns about. This new paper is largely addressing bucket bias in sea surface temperature and is very detailed. Taken with his other work on temperature records, this has to cement Kevin Cowtan's place among the "serious climate nerds" (h/t ykw!)

A hybrid check on sea surface temperature bias corrections

The authors analysed sea surface temperature, the main source of the temperature blips, from a new perspective. Their analysis can be seen mainly as a check of the bias corrections used in other sea surface temperature records. Instead of reanalysing data from ships and buoys, they compared weather stations on the coast and on islands with the measurements taken on ships when they passed close to the coast. They subjected this to further analysis and called the result a hybrid SST (sea surface temperature).

I can only imagine how much work this must have entailed. There are hints in the paper. Not only did they get the temperature records from land and nearby sea, they made adjustments in their analysis to compensate for the fact that with global warming, the land surface is warming faster than the sea surface, plus more.

They used their results to assess the bias correction that needs to be made when the sources for sea surface temperature changed, such as from buckets to engine intake, and to buoys (see below). The end result was a different check on sea surface temperatures and additional evidence that:

• Some of the odd blips in the temperature records were not what actually happened - particularly the upward WWII blip and the drop down around 1910
• The NOAA sea surface temperature record from 1997 onwards is probably closest to reality. On the other hand, the Cowtan17 analysis indicates ERSST v4 is too warm in the earliest years (1860 to 1900 or so) and too cool in the early 20th century (1910 to late 1930s).
• Climate models reflect reality even more closely than previous records suggest. 

There's an excellent article on Kevin Cowtan's website which explains the research, and accompanying provisos. The paper and supporting information contain a lot more detail, including all the ifs and buts and maybes. Co-author Zeke Hausfather has a  Twitter thread about the paper, too.

Challenges in the historical record of sea surface temperature

The authors begin by pointing out that getting a record of sea surface temperature is more challenging in many ways than putting together land temperature records. The difficulty with sea surface temperature is that information sources change much more than those on land.

On the land, apart from getting as many records together as possible (thank you CRU and other early collectors, and more recently ISTI), the main issues to contend with are adjusting for changes in instrument design and location. Location changes can be identified from station records or inferred from abrupt changes in the record compared with neighbouring records. Technological change hasn't happened all that often in the past 150 years or so. The main ones include the introduction of the Stevenson screen way back, and the more recent shift to automatic weather stations with resistance probes replacing mercury thermometers.

On the sea, the problems include the different sources for temperature readings: buckets of differing materials being dipped into the sea, engine room intakes, sensors on the ships hull and, more recently, drifting buoys and satellites. Within all that, scientists have to account for things like changes in the height of ship decks, interruptions to the consistency of records caused by world wars (where the data source changed from predominately merchant ships to predominately naval vessels), and more. The marvel is that researchers have worked through all these difficulties and developed records of sea surface temperature going back many decades.

Questionable peaks and troughs in the SST records - WWII and all that

One period about which most scientists who've worked on the subject have had most issue with are the years of the second world war (WWII). Some data sets show a peak in temperature that has not been easily explained by weather or climate change phenomena. In addition, previous records show a drop in the temperature around 1910 that looks a bit odd. In this paper, the authors did not find the spike that exists in ERSST v5 and to a lesser extend in HadSST3. Neither did they find the drop in temperature in the early 1900s.

In the top chart below, the hybrid record is shown in blue. The different series are a bit hard to distinguish so you might want to click on the image to enlarge it.

Figure 1 | Comparison of the coastal hybrid temperature reconstruction (using all coastal stations and fitting the global mean of the coastal temperature differences only) to co-located data from HadSST3 and ERSSTv5 for the period 1850-2016. Spatial coverage is that of HadSST3 for all of the records, with coastal cells weighted by ocean fraction.The shaded region is the 95% confidence region for the HadSST3 anomalies including combined bias adjustment and measurement and sampling errors. The lower panel shows the adjustment applied to the raw data in the HadSST3 and coastal hybrid records. A comparison with the ERSSTv4 ensemble is shown in Figure S7. Source: Cowtan 17 Figure 12.

To help see the difference, the chart below compares the Cowtan17 hybrid record with NOAA's ERSST v4 record. As discussed, the two are very similar in the most recent decades, but differ much more in the period prior to the early 1940s.

Figure 2 | Comparison of coastal hybrid temperature reconstruction to the ERSSTv4 ensemble. The dotted line is the ensemble median, while the shaded region is the 95% range of the ERSSTv4 1000 member ensemble from Huang et al (2016). DOI: 10.1175/JCLI-D-15-0430.1 . Source: Cowtan17 supporting information Figure S7

The table below highlights further that the Cowtan17 analysis is closer to the NOAA data set for the period after WWII since 1997 than it is to the Hadley record (HadSST3). The trend of HadSST3 is lower than that found in Cowtan17 and ERSST v4.

Table 1: Trend in sea surface temperature since 1997. Source: Cowtan17 Supporting Information Table S2.

The analysis supports the CMIP5 models

Another thing the analysis suggests is that there is less of a difference between observations and the blended mean from CMIP5 model runs. This is shown in the chart below, from Kevin Cowtan's briefing paper, where the green line is the CMIP5 blended mean.

Figure 3 | Comparison of global temperature records based on either the UK Met Office sea surface temperature record (HadSST3), or our coastal hybrid record. The smoothed records are compared to the average of climate model simulations from the CMIP5 project. The lower panel shows the differences between each set of observations and the models. Source: Kevin Cowtan's blog article.

Constraints and provisos

The authors of Cowtan17 show a lot of restraint and go into quite a bit of discussion of uncertainties and provisos. They present their findings not as the be all and end all of temperature reconstruction, but as a suggestion of where to investigate further. Kevin Cowtan wrote in his briefing:

However we do not necessarily trust our new record, because of the assumptions we had to make in constructing it. The most important result of our work may therefore be to identify places where extra attention should be given to addressing problems in the existing sea surface temperature records. A secondary result is that caution is required when trying to draw conclusions about any differences between the models and the observations, whether it be to identify internal cycles of the climate system or problems in the models, because the differences that we do see are mostly within the range of uncertainty of the observations.

Just the same, this paper has a lot of merit, looks at the data differently, and shows that the spurious peaks and troughs from years gone by may indeed be out of whack. It also supports the records in recent times, which seems to me to add weight to their findings.

What deniers are saying about Cowtan17

Nothing. At least nothing at WUWT or anywhere else that I've seen. Either they all missed the paper because it came out in the holidays, or they haven't figured out what to say about it.

References and further reading

Cowtan, K., Robert Rohde, and Zeke Hausfather. "Evaluating biases in Sea Surface Temperature records using coastal weather stations." Quarterly Journal of the Royal Meteorological Society (2017). DOI: 10.1002/qj.3235 (pdf here)

• Evaluating biases in Sea Surface Temperature records using coastal weather stations - overview, briefing document, links to methods and data and more from Kevin Cowtan
• Twitter thread from Zeke Hausfather

Happy holidays and all that

Wishing everyone greetings of the season, whatever the season is for you - winter, summer, Christmas, new year or  just an excuse for a holiday if you are fortunate enough.

If you've noticed I've been a bit distant this past few months, I'll be back in the new year and may even sneak in a couple of blog articles before then.

Thanks for all your support this past year, and best wishes for 2018.

Confirmation bias affects visual perception at WUWT - on carbon trading in China and the LA Times

Anthony Watts has posted an article by a bloke called Larry Hamlin, which is a stark example of how confirmation bias affects visual perception. Larry is a climate science denying conspiracy theorist who has the occasional "essay" at WUWT.

He wrote about something he read in the LA Times. It was a recent announcement from the Chinese government that it is preparing to set up what will eventually be a nationwide carbon trading program. The article was by Jonathan Kaiman reporting, from Beijing, a news conference of the National Development and Reform Commission in China.

The article set out the timetable, which stated that it would be three years before transactions begin (my emphasis):

China’s carbon market will initially apply only to the power-generation industry but will later expand to cover seven other sectors, including petrochemicals, chemicals, building materials, and iron and steel.

The Chinese government will spend a year building a nationwide registration system covering all companies participating in the market, the state-run China Daily reported. It will spend another year testing the system, and actual transactions will begin in about three years.

Has Anthony Watts just claimed he's on Scott Pruitt's #climate science denying "Red Team"?

Scott Pruitt
Gage Skidmore/Flickr (CC BY-SA 2.0)

You may have heard that the EPA Secretary, Scott Pruitt, keeps promising to put together a "Red Team" to support him in his rejection of climate science. He's getting names from various unsavoury organisations, I gather. I doubt any of those organisations have suggested WUWT owner and promoter of "climate hoax" conspiracy theories, Anthony Watts. However, it looks as if Anthony is hinting he's on the team.

I stumbled across something at WUWT this morning that suggests this. It was in among a lot of self promotion as an AGU member "in good standing", some misogyny, and various other rantings from Anthony. (What are the criteria for good vs bad standing among AGU membership? If it ever decided to draw a line Anthony would never appear on the "good" side.)

Here's what Anthony wrote, implying that he is already on Scott Pruitt's "Red Team". He was writing how he dislikes New Orleans and doesn't think he'd get enough money from his fans to go this year, so he won't try (or something like that :D). (AGU17 is at New Orleans.) Then he wrote how it's not a bad thing he won't be going, saying:

Polar bears, sexism and climate science denial

Adult polar bear on the look-out.
Source: Ian Sterling

When a science paper about polar bears generates multiple articles on denier blogs you can see it has hit a nerve. This happened recently when a paper was published, with a classic illustration of how deniers reference each other to make out there is dispute about climate change impacts.

The paper was by Jeffrey A Harvey and a bunch of other leading scientists. When I say a bunch, there were fourteen scientists listed as authors, comprising rising stars and heavyweights in the climate science world.

It's fortunate I wasn't able to write about this paper when it was first released because it allowed time to see the numerous articles about it on denier blogs. However, before looking at deniers' various reactions, how about a quick summary of the paper. It's open access and is easy to read. It may help if you understand the analytical techniques used, though that's not essential.

Funny peculiar: #Climate "guru" Anthony Watts' doesn't know the oceans accumulate energy

Two days ago Anthony Watts, who runs a climate conspiracy blog WUWT, posted what he called "Friday Funny – Climate Central’s scare graph excuse: ‘The oceans ate the warming’".

It is funny, as in odd, peculiar, that Anthony Watts doesn't know that more than 90% of the extra energy we've been adding is stored in the ocean. I mean, Anthony makes himself out to be an expert on climate change, more expert than the experts who research the subject. He's been blogging about climate for about ten years now. To think that he doesn't know one of the most basic facts about global warming is very strange indeed.

Second hottest October on record, just above October 2016

Summary: October 2017 was the second hottest October on record. The 12 month period to October 2017 was the second hottest November to October period on record.

According to GISS NASA, the average global surface temperature anomaly for October was 0.90 °C, which is 0.18 °C less than the October 2015. October 2017 was just 0.01 °C hotter than the next hottest October in 2016.

Below is a chart of the average of 12 months to October each year. The 12 months to October 2017 averaged 0.90 °C above the 1951-1980 mean, which was 0.13 °C cooler than the 12 months to October 2016.

This makes it the second hottest September to October 12 month period on record.

"Climate hoax" conspiracy theorists don't value logic or evidence - who knew :)

In a copy and paste at WUWT, Anthony Watts highlights a paper with research suggesting why WUWT-ers are so willing to adopt their "climate hoax" conspiracy theories. The researchers, Tomas Ståhl and Jan-Willem van Prooijen argue that people holding irrational beliefs (such as Anthony Watts and his ragtag mob of climate hoax conspiracy theorists) lack analytical skills and/or don't value logic or evidence.

Even if one or two WUWT deniers were endowed with reasonably high cognitive skills, evidence suggests they wouldn't value these skills and therefore don't use them. When it comes to climate science, they discard those skills in favour of one of the myriad conspiracies Anthony touts.

In the abstract of the paper itself, the authors write about how both analytical skills and motivation to be rational are required if one is to avoid adopting silly and unfounded beliefs:

We propose that part of the reason why unfounded beliefs are so widespread is because skepticism requires both sufficient analytic skills, and the motivation to form beliefs on rational grounds. 

It's immediately obvious to anyone who reads the articles and comments at WUWT that the bulk of Anthony's commenters lack a lot more than the motivation to be rational. Most of them lack analytical skills. Oh, there are still a few WUWT fans who can string words together to form whole sentences, but they are few and far between.

Give us your climate predictions, Andy May

Every so often WUWT publishes what it describes as "failed climate predictions". It is often timed to distract from more bad climate news, such as the fact that last year there was a record increase in the annual rise in atmospheric CO2.

The list published today, from Andy May at WUWT, follows the normal pattern. It takes a bunch of statements that were published at various times, including several from 27 years ago, and claims they are failed predictions. This includes statements that refer to things that may happen by 2100.

Yep, science deniers tend to oscillate between living in the past and living way ahead in the future. Tim Ball, one of Anthony's pet conspiracy theorists, rarely manages to emerge beyond 1970. Andy May (and Anthony Watts) both implicitly claim they have a time machine that has taken them into the future.

There are two other points worth making before I give you some examples of the low regard they (rightly) hold for WUWT fans. (They know they are a the dullest of the dim-witted.)

Anthony Watts is already crowing it hasn't warmed since 2016 (last year), with a La Niña watch

If you've been missing HotWhopper's take downs of deniers, you haven't been missing a lot. Wattsupwiththat is just repeating common denier memes over and over again.

In the last day Anthony Watts has even managed - it hasn't warmed since 2016 (therefore global warming is a hoax)! If you can believe that. (It's mostly true, though he only blew on the dog whistle and didn't spell out that last bit.)

He's a bit late to the party. The latest ENSO wrap-up from Australia's Bureau of Meteorology was an announcement of a La Niña watch, and that was last Tuesday. Here's an excerpt (my emphasis), which may disappoint the global cooling believers:

Seven of the eight international climate models surveyed by the Bureau suggest that sea surface temperatures will reach or exceed La Niña thresholds by November 2017. However, indicators need to remain at La Niña levels for at least three months to be considered an event. This is forecast by six of the eight models. If a La Niña does occur this year it is likely to be short and weak, as sea surface temperatures are forecast to warm again in early 2018, as the austral autumn is the time when La Niña events normally decay.