Summary: Today we look at one of the many interesting graphics from the leaked draft of the IPCC’s Fifth Assessment Report (AR5), this one showing the pause in global warming. And the various responses of scientists to this data. This is the latest in a series about the “pause” in global warming; see section 6 for more information).



Other posts in this series about second order draft (SOD) of the Fifth Assessment Report (AR5) by the Intergovernmental Panel on Climate Change (IPCC):

Contents

A powerful graphic A brief comment about the pause Three responses to this data Significance of the pause to non-scientists The warmistas’ response to the pause Other posts about the “pause” For More information

References omitted in excerpts from the IPCC report; red emphasis added.

(1) A powerful graphic

Alex Rawls leaked the draft of the IPCC’s Fifth Assessment Report (AR5). Figure 1.4 shows the actual temperature vs. the forecasts of the IPCC’s various models:

Caption to this graphic:

Estimated changes in the observed globally and annually averaged surface temperature (in °C) since 1990 compared with the range of projections from the previous IPCC assessments. Values are aligned to match the average observed value at 1990. Observed global annual temperature change, relative to 1961–1990, is shown as black squares.

Whiskers indicate the 90% uncertainty range of the Morice et al (2012) dataset from measurement and sampling, bias and coverage.

The coloured shading shows the projected range of global annual mean near surface temperature change from 1990 to 2015 for models used in {FAR, TAR, and AR4}.

The 90% uncertainty estimate due to observational uncertainty and internal variability based on the HadCRUT4 temperature data for 1951-1980 is depicted by the grey shading.

The IPCC models shown are:

FAR: 1990, the IPCC’s First Assessment Report

SAR: 1995, the IPCC’s Second Assessment Report

TAR: 2001, IPCC’s Third Assessment Report

AR4: 2007, the IPCC”s Fourth Assessment Report

(2) Update: A brief comment about the pause



From Chapter 10 – Detection and Attribution of Climate Change:

While the trend in global mean temperature since 1998 is not significantly different from zero, it is also consistent with natural variability superposed on the long-term anthropogenic warming trends projected by climate models.

See the (c) in the next section for more from AR5.

(3) Three responses to this data

The response of scientists associated with the IPCC to this divergence takes various forms, such as these three.

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(a) The models are getting better

In AR5, the new models are described as superior to the models used in past IPCC forecasts. But the older models were also presented originally as providing a reliable basis for massive public policy measures.

(b) An infamous defense

Often used, most clearly stated by Kevin E. Trenberth (Senior Scientist, Climate Analysis Section at the National Center for Atmospheric Research), “Predictions of climate“, Nature, 4 June 2007 — Excerpt:

In fact there are no predictions by IPCC at all. And there never have been. The IPCC instead proffers “what if” projections of future climate that correspond to certain emissions scenarios. There are a number of assumptions that go into these emissions scenarios. They are intended to cover a range of possible self consistent “story lines” that then provide decision makers with information about which paths might be more desirable. But they do not consider many things like the recovery of the ozone layer, for instance, or observed trends in forcing agents. There is no estimate, even probabilistically, as to the likelihood of any emissions scenario and no best guess.

Despite Trenberth’s assertion, the IPCC reports are littered with descriptions of the model outputs as “forecasts”. And their outputs are presented to the public and policy-makers as forecasts, the basis for large-scale public policy action.

(c) The pause is “consistent with” the models

While analytically accurate, statements that such a wide range of outcomes is “consistent with” the models shows that today they provide a weak basis for large-scale public policy action. See these excerpts from the draft AR5.

Chapter 2: Observations: Atmosphere and Surface

Much interest has focussed on differences in the period since 1998 and an apparent flattening in HadCRUT3 trends. … all products now show a warming trend since 1998 HadCRUT: 0.055 °C per decade ;

; MLOST: 0.042 °C per decade ;

; GISS: 0.093 °C per decade . None of these are statistically significant.

Chapter 10: Detection and Attribution of Climate Change

Global mean surface temperatures have not increased strongly since 1998, a period over which the multi model mean simulated temperature increased in response to steadily increasing greenhouse gas concentrations and constant or declining aerosol forcing. A key question, therefore, is whether the recent apparent slowdown in the rate of observed global warming is consistent with internal variability superposed on a steady anthropogenic warming trend (for example, as represented by the spread of model trends over the same time), or whether it has been driven by changes in radiative forcing. It is found that global temperature trends since 1998 are consistent with internal variability overlying the forced trends seen in climate model projections … Liebmann et al. (2010) conclude that observed HadCRUT3 global mean temperature trends of 2–10 years ending in 2009 are not unusual in the context of the record since 1850. After removal of ENSO influence, Knight et al. (2009) concluded that observed global mean temperature changes over a range of periods to 2008 are within the 90% range of simulated temperature changes in HadCM3. Over the period 1999–2008, ENSO contributed a warming influence, so the lack of warming seen in the global mean temperature over this period cannot be attributed to ENSO.

(4) Significance of the pause to non-scientists

The pause in global warming, now roughly 15 years long, is clearly seen in the major climate data sets. It has been acknowledged by many prominent climate scientists. It has been the subject of much study in peer-reviewed publications. We look at examples of all three in these two posts.

The pause should not surprise anyone familiar with the current state of climate science. The relative importance of the many causes of the two century-long warming remain uncertain (only since 1950 has anthropogenic CO2 been the largest driver). There are many factors at work: natural cycles, volcanoes, solar cycles, emissions of CO2 and aerosols, land use changes — and feedbacks (eg, warming on atmospheric humidity). Some of these are poorly understood. This makes reliable forecasts difficult, especially to the degree required before re-shaping the world economy.

That’s the import of the pause. The long warming will resume, continue, or end. Climate scientists will analyze its causes and continue to improve their models. But the for today the warming pause should make us pause for thought before taking drastic action. The standard of proof required for public policy must be higher than that for academic study. The unexpected nature of the pause (appearing in the literature only after its appearance in the data), suggests that climate science models might not yet provide a reasonable basis for large-scale public policy action.

(5) A common reaction to the pause from non-scientists

But we see something far different from the chorus of the lay global warming cheerleaders. For example, the comments to these posts, and others mentioning this subject, are largely demonstrations of the first rule of warmistas:

Scientists are authorities, until they challenge global warming dogma. They they’re clowns and charlatans.

Warmistas tend to avoid real science like vampires do holy water. This is the Left’s equivalent to the anti-rationalism that has come to dominate the far Right, both of which prime components of America’s broken Observation-Orientation-Decision-Action loop. We cannot see the world clearly through our thick ideological filters. So our responses don’t work.

Please post your solutions to this in the comments.

(6) Other Posts about the “pause”

(7) For More Information

Posts describing new science research, and statements by scientists:

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