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.
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.
|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.|
|Figure 2 | Conceptual visualiation of the sliding 15-year "window" in Risbey15. Source: HotWhopper July 2014.|
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.
From the WUWT comments
Francisco did at least read the fine print:
February 24, 2016 at 9:29 am
I find it interesting that the caveat/excuse/party line is always given and cannot just refute the scam: “Fyfe uses the term “slowdown” rather than “hiatus” and stresses that it does not in any way undermine global-warming theory.”
gymnosperm picked up on the fine print too, though he or she doesn't like it:
February 24, 2016 at 9:35 am
” 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 century4. 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?
On the other hand, Tom Halla wrongly thinks that Karl15 is "wrong". It's not wrong;
February 24, 2016 at 9:37 am
So Karl et al is wrong even after altering buoy’s to match ship cooling water intakes? I would think the real probem is reconciling Karl with RSS and UAH.
I think that Flaxdoctor is the first to notice Professor Mann among the authors:
February 24, 2016 at 9:56 am
Check out the list of authors. It includes one Michael E (Piltdown) Mann. Has he abandoned ‘The Cause’, or is he up to something devious yet again?
Jpatrick thinks there is some sort of disconnect. There's not. January was the hottest January on record. 2015 was the hottest year on record.
February 24, 2016 at 9:59 am
A couple days ago I just finished reading how January 2016 was the hottest EVER! The disconnect just amazes me. Meanwhile, I wonder if Lake Superior is getting ready to freeze over again.
Robert Doyle doesn't know that there was no slowdown in ocean heating, and water expands when it gets hot. (Ice melts in the heat, too.)
February 24, 2016 at 9:59 am
So, Climate Central took the opportunity to go “wall to wall” reporting dramatic sea level rise. It was picked up everywhere! New York City and Washington, DC were again under water. Oh, the humanity.
Tell us, the unwashed how the acceleration happened during the “pause”? Maybe, could it be that, sea levels are not correlated to CO2?
A couple more people were befuddled by the authors, and undoubtedly befuddled by the paper. mpcraig wrote:
February 24, 2016 at 10:00 am
I just looked at the authors of that study. Say what??
February 24, 2016 at 10:20 am
That really is a riddle to me. 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
dbstealey doesn't care what this or any scientific paper says. He doesn't care that 2005, 2010, 2014 and 2015 were all the hottest years on record at the time. He'll continue his disinformation campaign claiming global warming has stopped and accuse all the world's climate scientists of belonging to a cult.
February 24, 2016 at 11:09 am
This is hair-splitting: ‘Pause’, ‘hiatus’, ‘plateau’, etc., etc.
Fact: global warming stopped many years ago. Thus, the endless parsing, hair-splitting, and refusal to face reality by the climate alarmist cult.
jjs claims that Obama (and every US President since at least Lyndon Johnson) wants to have to deal with the biggest problem facing humanity, and falsely accused NOAA scientists of fraud:
February 24, 2016 at 11:02 am
Thomas Karl, director of NOAA’s National Centers for Environmental Information – this man did not get to the level of director without towing the company line, no matter the truth. He provided the customer with what they want. NOAA’s company line is determined by who their biggest customer/boss is and that be the Obama administration.
Only a fool would believe anything that comes out of government at the Federal level. Sad but true at this point in our nation.
References and further reading
Mann, Michael E., Stefan Rahmstorf, Byron A. Steinman, Martin Tingley, and Sonya K. Miller. "The Likelihood of Recent Record Warmth." Scientific reports 6 (2016). doi: 10.1038/srep19831 (open access)
Trenberth, Kevin E. "Has there been a hiatus?", Science 14 August 2015: Vol. 349 no. 6249 pp. 691-692 DOI: 10.1126/science.aac9225
Karl, Thomas R., Anthony Arguez, Boyin Huang, Jay H. Lawrimore, James R. McMahon, Matthew J. Menne, Thomas C. Peterson, Russell S. Vose, and Huai-Min Zhang. "Possible artifacts of data biases in the recent global surface warming hiatus." Science 348, no. 6242 (2015): 1469-1472. DOI: 10.1126/science.aaa5632
Niamh Cahill, Stefan Rahmstorf and Andrew C Parnell. "Change points of global temperature". 2015 Environ. Res. Lett. 10 084002. doi:10.1088/1748-9326/10/8/084002 (open access)
Grant Foster and John Abraham. "Lack of evidence for a slowdown in global temperature." US CLIVAR Variations • Summer 2015 • Vol. 13, No. 3 (open access)
Fyfe, John C., Nathan P. Gillett, and Francis W. Zwiers. "Overestimated global warming over the past 20 years." Nature Climate Change 3, no. 9 (2013): 767-769. doi:10.1038/nclimate1972 (pdf here)
From the HotWhopper archives
- On Seeps and SCAMS Part I: Lessons for Climate Scientists - May 2015
- James Risbey and co: Another perspective on surface temperature observations and climate models - July 2014
- NOAA: No pause in the global surface temperature - June 2015
- Global Warming and the Pacific: Kevin Trenberth's Perspective - August 2015
- Global sea surface temperature and model projections, with Bob Tisdale - February 2016