Thursday, March 2, 2017

Fyfe 2016, Global Warming Hiatus? Nope. Not even!

I've been spending the past couple days digesting Fyfe 2016 on account of John Bates, and his ClimateEtc hit-piece, which uses it to imply the global warming ‘hiatus’ was a real thing >>> Mind you “hiatus" = "A pause or gap in a sequence, series, or process.”:
J. Bates writes: "The most serious example of a climate scientist not archiving or documenting a critical climate dataset was the study of Tom Karl et al. 2015 (hereafter referred to as the Karl study or K15), purporting to show no ‘hiatus’ in global warming in the 2000s (Federal scientists say there never was any global warming “pause”). The study drew criticism from other climate scientists, who disagreed with K15’s conclusion about the ‘hiatus.’ (Making sense of the early-2000s warming slowdown)" 
Link to a readable Fyfe et al. 2016:
When I read Fyfe 2016 I was stunned and appalled by how it was worded.  Yet, it’s co-authored by some of the foremost climate scientists in the world.  A couple having endured vicious and vile attacks fabricated out of pure lies at the hands of the Republican PR campaign of climate science deception.  Scientists whom I consider genuine heroes.  I am under no illusion.  I cannot dispute their facts, but it's the way their facts were presented that seems to me a prime example of the “Seepage” suffered by well meaning, but extremely conservative and cautious scientists, playing right into the Contrarian’s Script, rather than clarifying how our global heat and moisture distribution engine operates in a manner were it can “click” with non-sciencie citizens.

Before I post my critique, which is far from finished, I want to share what Sou at HotWhopper has to say.  She was trained as a scientist so approaches this paper differently than I do, from my own street-level perspective, that of a high school grad (‘73) lay-person, albeit one that’s spent a lifetime paying attention to developing Earth Sciences and the evolving insights they’ve offered into Earth’s fantastical pageant and our place in that pageant.
Therefore I think it appropriate to first REPOST her article of February 25th.  She explains the scientific perspective in a way I never could.  I’m going to begin with her closing paragraph because that’s exactly what I’m struggling with.  I also a thank you Sou, for allowing me to repost your work.

Global surface warming continues without pause contrary to denier claims
Sou | Feb 25, 2016

I want to start with Sou's closing paragraph since it echoes the thing that got under my skin and that my review is struggling to articulate.
This is a useful paper from a scientific perspective. 
From the perspective of informing the public, I would have preferred the authors were more constructive rather than making it appear there are disputes in scientific circles when there aren't.  
Deniers aren't going to read the paper. They aren't going to care that there was no change in the long term trend. They aren't going to care that the models differed from observations because the estimated forcings were wrong. All they are going to do is point to the paper falsely claiming it is "evidence" that scientists disagree, when on these issues there would be very little disagreement (if any) among climate scientists.  
Or they'll do as Anthony Watts {and also John Bates}  did, and point to the paper claiming there was a "hiatus" or stopping of global warming, when there isn't and hasn't been. 

There's another new paper out in Nature Climate Change today that discusses the recent trends on global surface temperature. It's by a rash of notable authors: John C. Fyfe, Gerald A. Meehl, Matthew H. England, Michael E. Mann, Benjamin D. Santer, Gregory M. Flato, Ed Hawkins, Nathan P. Gillett, Shang-Ping Xie, Yu Kosaka, Neil C. Swart. Anthony Watts heralded the paper (archived here), which is unusual because he normally scoffs at the findings of most of these authors. He referred to an article in the Examiner newspaper, which claims that this paper contradicted "another study last June" that stated that the "the hiatus was just an artifact that “vanishes when biases in temperature data are corrected.”

Well it doesn't contradict it. Needless to say Anthony and the Examiner was comparing apples and oranges.

The new paper, Fyfe16, discussed the reality of the slowdown. There was no "hiatus" or stopping of global warming, contrary to Anthony Watts' headline. The rise in global surface temperatures slowed down earlier this century compared to the rate of rise from the mid-1970s to the late 1990s. As Jeff Tollefson of Nature wrote about the lead author: "Fyfe uses the term “slowdown” rather than “hiatus” and stresses that it does not in any way undermine global-warming theory."

I'll point out that other papers that have looked at change points in the longer term trend detected no change since the beginning of the 1970s. So the slowdown in the early 21st century wasn't enough to change the longer term trend.

The paper begins by stating:

A large body of scientific evidence — amassed before and since the Fifth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC AR5)1 — indicates that the so-called surface warming slowdown, also sometimes referred to in the literature as the hiatus, was due to the combined effects of internal decadal variability and natural forcing (volcanic and solar) superimposed on human-caused warming2. Given the intense political and public scrutiny that global climate change now receives, it has been imperative for scientists to provide a timely explanation of the warming slowdown, and to place it in the context of ongoing anthropogenic warming. Despite recently voiced concerns, we believe this has largely been accomplished.

From where I sit, there's no conflict between the scientific papers on the subject, whether it's Karl15, Trenberth15 or Fyfe16. It's being presented as a controversy by some of the authors and journals, but the evidence presented by all of them is consistent. All that's happened is that some authors are emphasising the fact that global warming hasn't stopped, while others are emphasising the fact that there was a relatively short period recently when global surface temperatures didn't go up as quickly as they did in the late twentieth century. For example this new paper opens with the provocative statement:

It has been claimed that the early-2000s global warming slowdown or hiatus, characterized by a reduced rate of global surface warming, has been overstated, lacks sound scientific basis, or is unsupported by observations. The evidence presented here contradicts these claims.

It's a tempest in a teacup. All this sort of silly posturing does is confuse the public. It also gives science deniers an opportunity to gloat and show their inconsistent cherry-picking approach to climate science.

FWIW, I disagree with the authors of Fyfe16 when they talk of "overstated". There have been a number of people who have overstated the slowdown in warming, almost all of whom have been science deniers. Many of these "overstaters" have falsely claimed (and continue to claim) that global warming has stopped. If that's not "overstating" then I don't know what is. 

As for there being a "sound scientific basis", unless the authors of Fyfe16 are talking about science deniers, then I'm not aware of anyone who disputes the fact there was a short term slowdown in surface warming, or the scientific explanations. As the authors of Fyfe16 show in their paper, the recent "slowdown" (which now seems to have stopped) looks different depending on when you pick the start and end dates, and on what period you compare it to.

To elucidate, there are a number of main points relating to recent global surface temperatures:
Global warming continues. It has not stopped or paused or hiatused.
The global mean surface temperature didn't rise as quickly early this century, compared to the rate of rise from the 1970s to the late 1990s.
There was a wider than expected gap between climate model projections and global mean surface temperature from the time that the forcings were estimated (2006 onwards) to around 2013). Climate models underestimated the negative forcing from volcanic aerosols and overestimated the positive forcing from solar radiation.
When climate models are populated with the observed forcings, then models match observations
Science deniers beat up the slowdown and paint it as "global warming stopped", when it didn't and hasn't, aka seeps and scams.
There is no observed slowing or stopping of the heat being accumulated in the oceans, where about 93% of the heat is going.

Here is the Rahmstorf chart (again) updated from Mann15, showing how there's no difference to speak of between models and observations once the correct forcings are plugged into the models:


Figure 1 | Global mean surface temperature and CMIP5. The CMIP5 multi-model mean has been updated with recent forcings and GISTemp data includes 2015 observations. Source: Stefan Rahmstorf, updated from Mann15 article in Nature's Scientific Reports.
So what does this new paper add to the understanding of global warming? Well, apart from reviewing some of the literature, the authors did something similar to what Risbey et al did in 2014. They ran a moving window over the global mean surface temperatures and compared it to models. Below is how I portrayed what Risbey2014 showed. As I said at the time, the graphic isn't meant to be accurate, it's indicative of their method:

Figure 2 | Conceptual visualiation of the sliding 15-year "window" in Risbey15. 
Source: HotWhopper July 2014

In the case of Fyfe16, the authors wrote how they used different sized windows:

To illustrate such issues, and to place the slowdown in the context of longer term trends and variability, we compute overlapping trends using 15-year, 30-year and 50-year windows starting in 1900. Using overlapping windows to characterize the slowdown is preferable to the practise of defining the slowdown based on arbitrary start and end dates (for example, refs 4, 8 and 9). Figure 2a–d compares observed overlapping trends against a measure of model uncertainty in simulated overlapping 15-year trends.

In all three observational datasets the most recent 15-year trend (ending in 2014) is lower than both the latest 30-year and 50-year trends. This divergence occurs at a time of rapid increase in greenhouse gases (GHGs)1. A warming slowdown is thus clear in observations; it is also clear that it has been a ‘slowdown’, not a ‘stop’. The slowdown was more pronounced in earlier observational datasets, and in studies based on them. Note also that the most recent observed 15-year trend is lower than the majority of simulated trends; common peaks in the modelled and observed overlapping trends centred around 2000 reflect similar recovery from the Pinatubo eruption in 1991. 

The  Fyfe16 authors also showed how internal variability was responsible for some of the slowdown. In particular, this was a time when the Interdecadal Pacific Oscillation (IPO) was in a cool phase. The IPO is similar to the PDO (Pacific Decadal Oscillation), but covers a bigger area of the Pacific. When it's in its cool phase, "cool" La Ninas are more pronounced than El Ninos. The authors wrote:

A different perspective on the role of internal variability is obtained through the analysis of the individual models and realizations comprising the MME. In 10 out of 262 ensemble members, the simulations and observations had the same negative phase of the IPO during the slowdown period — that is, there was a fortuitous ‘lining up’ of internal decadal variability in the observed climate system and the 10 simulations15,16. These 10 ensemble members captured the muted early-twenty-first-century warming, thus illustrating the role of internal variability in the slowdown. 

Again, this is not dissimilar to the findings in Risbey2014, in which the authors compared models where ENSO events lined up with the timing of ENSO events in the real world. Also the perspective piece by Kevin Trenberth that I wrote about some time ago.

In another part of the Fyfe16 paper, the authors refer to the main "hiatus" period in global warming, which occurred from the 1950s to the 1970s. They wrote:

During this period, increased cooling from anthropogenic sulfate aerosols roughly offset the warming from increasing GHGs (which were markedly lower than today). This offsetting contributed to an approximately constant GMST. Ice-core sulfate data from Greenland support this interpretation of GMST behaviour in the 1950s to 1970s, and provide compelling evidence of large temporal increases in atmospheric loadings of anthropogenic sulfate aerosols. The IPO was another contributory factor to the big hiatus13.

In Cahill15, the change point analysis paper, the authors found trend changes illustrated in the chart below. You can see where the only "hiatus" was since 1920. The most recent "slowdown" doesn't make the cut:
Figure 3 | Overlaid on the raw data are the mean curves predicted by the three CP model. The grey time intervals display the total range of the 95% confidence limits for each CP. The average rates of rise per decade for the three latter periods are 0.13 ± 0.04 °C, −0.03 ± 0.04 °C and 0.17 ± 0.03 °C for HadCRUT, 0.14 ± 0.03 °C, −0.01 ± 0.04 °C and 0.15 ± 0.02 °C for NOAA, 0.15 ± 0.05 °C, −0.03 ± 0.04 °C and 0.18 ± 0.03 °C for Cowtan and Way and 0.14 ± 0.04 °C, −0.01 ± 0.04 °C and 0.16 ± 0.02 °C for GISTEMP. Source: Cahill15
There were a few other points made in the new paper. I'll just comment on one more of them. The authors wrote:

The last notable decadal slowdown during the modern era occurred during the big hiatus. The recent decadal slowdown, on the other hand, is unique in having occurred during a time of strongly increasing anthropogenic radiative forcing of the climate system. 

It might have been "unique" so far, but that's probably because it's only in recent decades that there has been a "time of strongly increasing anthropogenic radiative forcing". It's probably going to happen again when the IPO is in a cool phase again in the future.

Look, I think this is a useful paper from a scientific perspective. From the perspective of informing the public, I would have preferred the authors were more constructive rather than making it appear there are disputes in scientific circles when there aren't. 

Deniers aren't going to read the paper. They aren't going to care that there was no change in the long term trend. They aren't going to care that the models differed from observations because the estimated forcings were wrong. All they are going to do is point to the paper falsely claiming it is "evidence" that scientists disagree, when on these issues there would be very little disagreement (if any) among climate scientists. Or they'll do as Anthony Watts did, and point to the paper claiming there was a "hiatus" or stopping of global warming, when there isn't and hasn't been.

One selected comment from WUWT

gymnosperm picked up on the fine print too, though he or she doesn't like it:

“researchers have found that climate models underestimated the cooling effect of volcanic eruption and overestimated the heating from solar radiation at the beginning of the twenty-first century. Other researchers are investigating variability in the Pacific Ocean”
Still floundering around looking for excuses. When will they get their thick heads around the reality that CO2 radiative functions need to be knocked back at least 50% in the models? When will they graduate from their high school conception of CO2 physics? 

This is the paranoid world view, they are all out to get ya, can't trust anyone but one's own self-certain biases.  Seems to me, there are plenty of modern marvels that depend on the scientists having gotten it right - even if I, or you, can't comprehend the details of the technology.

CO2 (physics) - Why We Can Be Sure.

Archive, Hanscom AFB Atmospheric Studies, 

Cambridge Research Lab

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