“There is this mismatch between what the climate models are producing and what the observations are showing,” says lead author John Fyfe, a climate modeller at the Canadian Centre for Climate Modelling and Analysis in Victoria, British Columbia. “We can’t ignore it.” Susan Solomon, a climatologist at the Massachusetts Institute of Technology in Cambridge, says that Fyfe’s framework helps to put twenty-first-century trends into perspective, and clearly indicates that the rate of warming slowed down at a time when greenhouse-gas emissions were rising dramatically.

– Jeff Tollefson, “Global Warming ‘Hiatus’ Debate Flares Up Again.” Nature, February 24, 2016.

It was officially noted in early 2016 with the above article in Nature, which was subtitled “Researchers now argue that slowdown in warming was real.”

I was reminded of this upon reading Pierre Gosselin’s recent post at NoTricksZone, “Global Temperature Rise Some 75% Lower Than Models Projected!” (July 18). His piece prompted vigorous debate where one commenter in particular presented a number of peer-reviewed articles affirming both the slowdown and global lukewarming as a vibrant position in the climate debate.

Some quotations follow:

“A millennial climatic oscillation would suggest that a significant percentage of the warming observed since 1850 could simply be a recovery from the Little Ice Age of the 14th – 18th centuries and that throughout the 20th century the climate naturally returned to a warm phase as it happened during the Roman and the Medieval warm periods.”

“We critically analyze the year 2015-2016, which has been famed as the hottest year on record. We show that this anomaly is simply due to a strong El-Niño event that has induced a sudden increase of the global surface temperature by 0.6 °C. This event is unrelated to anthropogenic emissions.”

“Herein, the authors have studied the post 2000 standstill global temperature records. It has been shown that once the ENSO signature is removed from the data, the serious divergence between the observations and the CMIP5 GCM projections becomes evident.”

“Since 2000 there has been a systematic tendency to find lower climate sensitivity values. The most recent studies suggest a transient climate response (TCR) of about 1.0 °C, an ECS less than 2.0 °C and an effective climate sensitivity (EfCS) in the neighborhood of 1.0 °C. …Thus, all evidences suggest that the IPCC GCMs at least increase twofold or even triple the real anthropogenic warming. The GHG theory might even require a deep re-examination.”

– Nicola Scafetta, , Aberto Mirandola, and Antonio Bianchini, “Natural climate variability, part 2: Interpretation of the post 2000, International Journal of Heat and Technology (2017).

“Ongoing scientific investigations continue to seek alternative explanations to account for the divergence of simulated and observed climate change in the early 21st century, which IPCC termed a ‘global warming hiatus.’ Understanding and communicating the causes of climate change in the next 20 years may be equally challenging.”

“Predictions of the modulation of projected anthropogenic warming by natural processes have limited skill. The rapid warming at the end of 2015, for example, is not a resumption of anthropogenic warming but rather an amplification of ongoing warming by El Niño.”

” … emerging feedbacks and tipping points precipitated by, for example, melting summer Arctic sea ice may alter Earth’s global temperature in ways that even the most sophisticated physical climate models do not yet replicate.”

– Judith Lean, “Observation‐based detection and attribution of 21st century climate change.” Climate Change. February 22, 2018.

“Land surface air temperature (Ta) is one of the fundamental variables in weather and climatic observations, modeling, and applications. Despite the ongoing increase in atmospheric greenhouse gases, the global mean surface temperature (GMST) has remained rather steady and has even decreased in the central and eastern Pacific since 1998. This cooling trend is referred to as the global ‘warming hiatus’.”

– Chunlue Zhou and Kaicun Wang, 2017, Spatiotemporal Divergence of the Warming Hiatus over Land Based on Different Definitions of Mean Temperature. Nature, 2017.

“During the first decade of the twenty-first century, the Earth’s surface warmed more slowly than climate models simulated.… Budgeting with existing observations cannot constrain the origin of the recent hiatus, because the uncertainty in observations dwarfs the small flux deviations that could cause a hiatus. The sensitivity of these flux deviations to the observational dataset and to energy budget choices helps explain why previous studies conflict, and suggests that the origin of the recent hiatus may never be identified.”

– Christoper Hedemann et al., 2017 “The subtle origins of surface-warming hiatuses.” Nature Climate Change 7 (2017)

“Despite continually increasing concentrations of greenhouse gas, there has been a hiatus in rising global temperatures during the 21st century.”

– Tao Xian and Yunfel Fu, “A Hiatus in the Tropopause Layer Change.” International Journal of Climatology, June 1, 2017

“Linear trends for three quasi-stable periods 1950-1987, 1988-1997 and 1998-2014 are near zero with nearly all warming occurring during two step-like shifts in the years 1987/1988 and 1997/1998. A notable consequence of the staircase dynamics of recent warming is that observed temperature anomalies (HadCRUT4.5) from 1950 till 2014 could be almost reproduced as the linear sum of only two factors(!) : ENSO variability and the staircase function.”

– P. V. Belohpetsky et al., “A staircase signal in the warming of the mid-20th century.” 15th International Conference on Environmental Science and Technology, September 2, 2017.

“[S]ince the mid-20th century, most observed warming has taken place in four events: in 1979/80 and 1997/98 at the global scale, 1988/89 in the Northern Hemisphere and 1968–70 in the Southern Hemisphere. Temperature is more step-like than trend-like on a regional basis. Satellite temperature is more step-like than surface temperature. … [S]tep-like changes are also present in tide gauge observations, rainfall, ocean heat content and related variables. [A]cross a selection of tests, a simple stepladder model better represents the internal structures of warming than a simple trend, providing strong evidence that the climate system is exhibiting complex system behaviour on decadal timescales. This model indicates that in situ warming of the atmosphere does not occur; instead, a store-and-release mechanism from the ocean to the atmosphere is proposed. It is physically plausible and theoretically sound.”

– Roger Jones and James Ricketts, “Reconciling the signal and noise of atmospheric warming on decadal timescales.” Earth System Dynamics, March 16, 2017.

More quotations, and the full comment debate, can be found here.