Summary: One of the major themes of the FM website is that The End of The World Will Not Occur as Scheduled. Publication of the new IPCC report sparked yet another round of doomsterism, quite unrelated to its contents. Today we look at the IPCC’s description of the climate science consensus. They warn about the future, but not of an imminent apocalypse. Sometimes the news media explain this well; sometimes they feature doomsters without mentioning the consensus. Here we look at the IPCC report for guidance. It’s quite clear. The consequences of failure to convert to non-carbon-based energy sources will be severe for the second half of the 21st century; but we have time if we start now (which we should do anyway, for sound environmental and economic reasons).
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Contents
- Excerpts from the Summary: the bottom line
- Expressing confidence and probabilities in AR5
- How much warming during the next two decades?
- About the “pause” or “hiatus”
- Important things to remember about global warming!
- For More Information
(1) Excerpts from the Summary: the bottom line
This posts discusses the report of Working Group I, part of the IPCC’s Fifth Assessment Report: The Physical Science Basis: Chapter 11: Near-term Climate Change: Projections and Predictability. This is a draft, because the IPCC adjusts the scientists’ work to conform to the politicians’ desires (political logical always overrides scientific evidence).
This chapter assesses the scientific literature describing expectations for near-term climate (present through mid-century). Unless otherwise stated, “near-term” change and the projected changes below are for the period 2016–2035 relative to the reference period 198 6–2005. …
The projected change in global mean surface air temperature will likely be in the range 0.3–0.7°C (medium confidence). …
It is more likely than not that the mean global mean surface air temperature for the period 2016–2035 will be more than 1°C (1.8°F) above the mean for 1850–1900, and very unlikely that it will be more than 1.5°C (2.7°F) above the 1850-1900 mean (medium confidence).
(2) Expressing confidence and probabilities in AR5
What makes the IPCC’s work science, not religion or organized ignorance, is that they state their conclusions in terms of uncertainty (comments to the climate posts on the FM website show how discovering this freaks out activists). From footnotes 1 and 2:
The level of confidence is expressed using five qualifiers: very low, low, medium, high, and very high.
In this Report the following terms have been used to indicate the assessed likelihood of an outcome or a result:
- Virtually certain 99–100% probability,
- Extremely likely: 95–100%,
- Very likely 90–100%,
- Likely 66–100%,
- About as likely as not 33–66%,
- Unlikely 0–33%,
- Very unlikely 0–10%
- Exceptionally unlikely 0–1%,
- More likely than not >50–100%, and
- Extremely unlikely 0–5%)
(3) How much warming can we expect to see during the next two decades?
Overall, in the absence of major volcanic eruptions and, assuming no significant future long term changes in solar irradiance, it is likely (>66% probability) that the GMST {global mean surface temperature} anomaly for the period 2016–2035, relative to the reference period of 1986–2005 will be in the range 0.3°C – 0.7°C {0.5°F – 1.3°F} (expert assessment, to one significant figure; medium confidence).
However, the implied rates of warming over the period from 1986–2005 to 2016–2035 are lower as a result of the hiatus: 0.10°C–0.23°C per decade, suggesting the AR4 assessment was near the upper end of current expectations for this specific time interval.
See Figure 11.9 — not the apocalypse. The lower end of this forecast sees almost no warming during the next 22 years. The upper end of the range requires a large acceleration from the trend of the past decade or two.
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(4) About the “pause” or “hiatus”
Whether from ignorance or mendacity, climate activists continue to ignore climate scientists’ work about the pause in warming since roughly 1998. For a prime example see “Who Created the Global Warming ‘Pause’?“, Chris Mooney, Mother Jones, 7 October 2013 — “How climate skeptics and the media — with a little inadvertent help from scientists themselves — forged a misleading narrative.” Not only did Mooney ignore the large literature describing the pause, he mocked the IPCC’s summary:
If the “pause” was just the result of statistical selectivity rather than a robust trend, why wasn’t the IPCC saying so? Instead, the scientists’ own words seemed to suggest that there really was a global warming slowdown, and that the scientific community didn’t really understand it.
It does not occur to Mooney that the IPCC said this because that’s what the literature says. Here’s one of the many similar passages from AR5 about the pause, from Chapter 11:
6) Over the last two decades the observed rate of increase in GMST {global mean surface temperature} has been at the lower end of rates simulated by CMIP5 models (Figure11.25a). This hiatus in GMST rise is discussed in detail in Box 9.2 (Chapter 9), where it is concluded that the hiatus is attributable, in roughly equal measure, to a decline in the rate of increase in effective radiative forcing (ERF) and a cooling contribution from internal variability (expert judgment, medium confidence).
Today’s models suggest that the pause might continue for two decades. If that happens, the activists crying “wolf” (e.g., attributing any severe weather to global warming, even when scientists and history say otherwise) might discredit not just themselves but climate science — and perhaps even science.
(5) A few important things to remember about global warming
While cheering for their faction of scientists, laypeople often lose sight of the big picture — the key elements for making public policy about this important issue.
(a) The work of the IPCC and the major science institutes are the best guides for information about these issues.
- The Elusive Absolute Surface Air Temperature (SAT), 18 August 2013
(b) The world has been warming during the past two centuries, in a succession of warming, cooling, and pauses. Since roughly 1950 anthropogenic causes have been the largest driver. Warming paused sometime in 1998-2000.
- When did we start global warming? See the surprising answer., 18 October 2012
- Still good news: global temperatures remain stable, at least for now., 14 October 2012 — Scientists analysis of the pause
- The IPCC sees the pause in global warming!, 18 December 2012
(c) There is a debate about the attribution (causes) of past warming — which probably varied over time — between natural drivers (e.g., rebound from the Little Ice Age, solar influences) and anthropogenic drivers (eg, CO2, aerosols, land use changes). Other that that stated in #3, the IPCC’s reports make few claims about attribution of climate activity, as this remains actively debated in the literature.
(d) There is an even larger debate about climate forecasts, both the extent of future CO2 emissions and the net effects of the various natural and anthropogenic drivers.
- One of the most important questions we face: when will the pause in global warming end?, 25 August 2013
- Possible political effects of the pause in global warming, 26 August 2013
(e) For the past five years my recommendations have been the same:
- More funding for climate sciences. Many key aspects (eg, global temperature data collection and analysis) are grossly underfunded.
- Wider involvement of relevant experts in this debate. For example, geologists, statisticians and software engineers have been largely excluded — although their fields of knowledge are deeply involved.
(f) Posts about preparing for climate change:
- How can we save the world from climate change?, 2 January 2013
- Preparing for the future: should we be precautionary or proactionary?, 22 August 2013
(6) For More Information
(a) Reference Pages about climate on the FM sites:
(b) Other posts in this series about global warming:
- Lessons about global warming from Alaska, 9 January 2013
- Secrets about global warming that you must not know, least they ruin the narrative, 22 January 2013
- Hidden news about our weather in July: experts tell us what even well-informed people do not know., 8 August 2013
(c) Posts about the larger aspects of the debate about global warming:
- Experts now run the world using their theories. What if they fail, and we lose confidence in them?, 21 June 2013
- Tell noble lies for America’s salvation!, 31 July 2013
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