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  1. #35001
    Iarmuid Iarmuid is offline
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    Reblogged from Judith Curry

    IPCC AR5 weakens the case for AGW | Climate Etc.

    IPCC AR5 weakens the case for AGW




    by Judith Curry

    Evidence reported by the IPCC AR5 weakens the case for anthropogenic factors dominating climate change in the 20th and early 21st centuries.



    The IPCC assessment reports have expressed increasingly confident consensus views of the importance of anthropogenic influence on the global climate over the past 60 years, as reflected by these statements from the Summary for Policy Makers (SPM):
    ◾AR4 (2007): “Most of the observed increase in global average temperatures since the mid-20th century is very likely (>90% confidence) due to the observed increase in anthropogenic greenhouse gases.” (SPM AR4)
    ◾AR5 (2013) SPM: “It is extremely likely (>95% confidence) that human influence has been the dominant cause of the observed warming since the mid-20th century .” (SPM AR5)

    This increase in confidence in the main conclusions in the AR5 SPM seems unwarranted based on the text, figures and analyses in the main WG1 Report, and also in comparison with the conclusions from the AR4. Several key elements of the report point to a weakening of the case for attributing the warming of human influences:

    ◾Lack of warming since 1998 and growing discrepancies with climate model projections


    Recent hiatus in surface warming and discrepancies with climate models

    The IPCC AR5 notes the lack of warming since 1998:

    [T]he rate of warming over the past 15 years (1998–2012) [is] 0.05 [–0.05 to +0.15] C per decade)which is smaller than the rate calculated since 1951 (1951–2012) [of] 0.12 [0.08 to 0.14] C per decade.

    The significance of this hiatus in warming since 1998 is in context of comparison with climate model projections. The IPCC AR4 stated:

    For the next two decades, a warming of about 0.2C per decade is projected for a range of SRES emission scenarios. (AR4 SPM)

    For the IPCC AR5, CMIP5 has produced a multi-model dataset that includes long-term simulations of twentieth-century climate and projections for the twenty-first century and beyond. The IPCC summarizes near-term projections of global mean surface temperature anomalies in Figure 1. Figure 1 shows that observations particularly since 2005 are on the low end of the envelope that contains 90% of the climate model simulations. Observations in 2011-2012 are below the 5-95% envelope of the CMIP5 simulations. The trend in the model simulations is substantially larger than the observed trend over the past 15 years.

    ...................................

    -After expecting an increase of 0.2oC per decade in the early decades of the 21st century from the AR4 statements, the rate of warming over the past 15 years is only ~0.05C.
    - The IPCC AR5 bases its projection for the period 2016-2036 of 0.10 to 0.23oC per decade on expert judgment, rather than on the climate model results
    - The IPCC does not have a convincing or confident explanation for the hiatus in warming.

    ...............................

    ◾Evidence of decreased climate sensitivity to increases in CO2
    ◾Evidence that sea level rise in 1920-1950 is of the same magnitude as in 1993-2012
    ◾Increasing Antarctic sea ice extent
    ◾Low confidence in attributing extreme weather events to anthropogenic global warming


    JC Summary



    If you read the fine print (not just the SPM) and compare the AR5 with statements made in the AR5, the IPCC AR5 WGI Report makes a weaker case for AGW than did the AR4. Of course there is nothing in the AR5 SPM that directly suggests weakening.
    Last edited by Iarmuid; 7th January 2014 at 11:23 AM.
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  2. #35002
    kront999 kront999 is offline
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    Quote Originally Posted by SirCharles View Post
    Just another day...


    Extreme Events: 06 January 2014

    Australia
    Severe thunderstorms hit southeast Queensland
    Indonesia
    Cloud of destruction: 20,000 evacuated as Mount Sinabung volcano erupts in Indonesia
    Indonesia extends volcano danger zone after Mount Sinabung eruptions
    Kenya
    Strong Winds Leave 1,500 Homeless
    South Africa
    ‘Worst drought in more than 80 years’
    Tonga
    Tropical Cyclone Ian approaching Tonga
    UK
    UK storms: Giant waves hit amid fresh flooding fears
    Wales weather: 250 people are evacuated as storms hit
    Storms: UK Braced For More Flooding And Chaos
    US and Canada
    North America weather: Polar vortex brings record temperatures
    US and Canada braced for more snow storms
    Heavy snowfall snarls travel in US north-east as temperatures plummet

    Other information of interest
    What is Polar Vortex? All About the Arctic Cyclone that Threatens US
    'Highly significant' heatwave smashes Australian records
    From Super Cyclone to Cyclone Phailin: Towards Odisha's Greater Investment in Disaster Risk Reduction
    What a warmer Australia means
    Publications
    Power Outages, Extreme Events and Health: a Systematic Review of the Literature from 2011-2012
    Impact of drought on vector-borne diseases – how does one manage the risk?
    This bulletin provides a summary of extreme event reports from public sources. Public Health England is not responsible for the content from external sites.
    Extreme Events and Health Protection Website
    Sent on behalf of:
    EXTREME EVENTS
    Extreme Events and Health Protection
    Wellington House
    133-155 Waterloo Road
    London SE1 8UG
    Tel No: +44 (0) 207 811 7143
    Fax No: +44 (0) 207 811 7759
    Email: ExtremeEvents@phe.gov.uk
    This service is provided to you at no charge by the Extreme Events and Health Protection Section,
    These guys need to talk to the MET services


    Climate models provide a broad range of projections about changes in storm track and frequency of storms. While there’s currently no evidence to suggest that the UK is increasing in storminess, this is an active area of research under the national climate capability.

    UK Weather: How stormy has it been and why? | Met Office News Blog
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  3. #35003
    Earthling Earthling is offline
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    They'll be giving them away before too long:

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  4. #35004
    owedtojoy owedtojoy is offline
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    Quote Originally Posted by Iarmuid View Post
    Dr Curry is entitled to her singular opinion, just as you are entitled to accept it uncritically if you want to.

    How she deduces that a move from ">90% confidence/ very likely" to "95% confidence/ highly likely" of human-dominated warming is "weaker" is unfathomable to me. It suggest a personal lop-sided view that is just wishful thinking.

    All her other points are just short-term, hopeful thinking that her stand of the past few years will be vindicated eventually. Antarctic ice and the mythical "pause" have been readily explained within the global warming paradigm. In other cases, it is easy to play around with short term trends - deniers do it all the time.

    It is good to see you and at last agree that the IPCC is being correctly cautious and not unduly alarmist.

    And then there is Professor Michael Mann arguing that the IPCC has been too conservative in its conclusions, especially in regard to the melting of ice:

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  5. #35005
    Earthling Earthling is offline
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    Quote Originally Posted by Steve Case View Post
    Are you really trying to tell me that the current cold snap in my
    neck of the woods these last two days is due to "Climate Change"?

    How dumb do you think I am?

    If you wanted to argue that the mild winters we've had here these
    last 25 years or so was due to a general climate warm-up with CO2
    as a significant part of that, I'd agree with you. But the cause of the
    current two day dip in temperature? No, you guys never know when
    to stop beating your drum. You have no credibility.
    Sidspamalot never has.
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  6. #35006
    owedtojoy owedtojoy is offline
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    Quote Originally Posted by kront999 View Post
    These guys need to talk to the MET services



    UK Weather: How stormy has it been and why? | Met Office News Blog
    Re-read the post.

    The Met Office statement is concerned with the UK only, the post with the planet as a whole.

    And there are an increasing output of papers that are connecting storms with global warming. As the Met Office said, it is a very active research area ...

    Increasing destructiveness of tropical cyclones over the past 30[thinsp]years : Abstract : Nature
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  7. #35007
    Earthling Earthling is offline
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    Quote Originally Posted by kront999 View Post
    Sources?

    How much of this ice loss is due CO2 induced warming!
    Sid would like you to believe that all ice loss is due to anthropogenic CO2 induced warming.
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  8. #35008
    Trainwreck Trainwreck is offline

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    Quote Originally Posted by Iarmuid View Post
    Thanks.

    Also add the wave of empiracally based (as opposed to model based) estimates of climate sensitivity are coming in lower and lower and the science is looking weaker and weaker.
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  9. #35009
    Iarmuid Iarmuid is offline
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    Quote Originally Posted by Trainwreck View Post
    Thanks.

    Also add the wave of empiracally based (as opposed to model based) estimates of climate sensitivity are coming in lower and lower and the science is looking weaker and weaker.
    Your welcome

    FYI from written submissions to UK Parliamentary inquiry into IPPC AR5, and congruent to your appendum.


    Submission

    N H Lewis submission to ECCC inquiry into AR5



    Introduction and summary
    The terms of reference for this inquiry ask various questions. I address the following questions; my related conclusions are italicised.
    How robust are the conclusions in the AR5 Physical Science Basis report (AR5-WG1)?

    In the central area of climate sensitivity, they are misleading. The substantial divergence between sensitivity estimates from, on the one hand, satisfactory studies based on instrumental observations over an extended period and, on the other hand, from flawed studies and from computer models was not brought out.

    Does the AR5 address the reliability of climate models?

    Not adequately. Shorter-term warming projections by climate models have been scaled down by 40% in AR5, recognising that they are unrealistically high. But, inconsistently, no reduction has been made in longer term projections.

    Do the AR5 Physical Science Basis report’s conclusions strengthen or weaken the economic case for action to prevent dangerous climate change?

    Although the conclusions fail to say so, the evidence in AR5-WG1 weakens the case since it indicates the climate system is less sensitive to greenhouse gases than previously thought.
    Climate sensitivity
    Climate sensitivity is a measure of how much the climate system warms each time the concentration of carbon dioxide in the atmosphere doubles. There are two principal measures used. Equilibrium climate sensitivity (ECS) is the amount of warming once the world ocean has fully warmed up, a process that takes more than a thousand years. ECS is believed to be a fairly stable property of the climate system, but is difficult to estimate accurately. Transient climate response (TCR) measures how much warming will take place over a 70-year period during which the carbon dioxide concentration doubles. TCR is easier to estimate than ECS, but may be less stable, and although more relevant to warming towards the end of the century is less useful than ECS when projecting over a wide range of timescales.
    Climate sensitivity is of direct policy relevance since it, and the level of uncertainty as to its value, is a key input into the economic models which drive cost-benefit analyses.
    Estimates of climate sensitivity have traditionally come from very complex computer models (GCMs) that simulate the global climate system. Attempts have also been made to calculate estimates based on paleoclimate data. However, in recent years it has become possible to calculate more robust values from instrumental observations of the climate, including surface and ocean temperature records and satellite data.[1]
    The IPCC considers all observational ECS estimates in AR5 WG1. It concludes that estimates based on
    paleoclimate data reflecting different past climate states
    climate response to volcanic eruptions or solar changes
    satellite measurements of short-term changes in heat radiation

    are unreliable and/or unable to provide usefully well-constrained estimates. I agree with this conclusion. That leaves in essence only estimates based on observations of warming over multi-decadal periods. Useful surface temperature records extend back approximately 150 years (the ‘instrumental period’). However, global warming ‘in the pipeline’ is predominantly reflected in ocean heat uptake, calculated from changes in sub-surface temperatures, records of which extend back only 50 years.

    There are two principal issues with the IPCC’s handling of the climate sensitivity area. Firstly the inclusion of sensitivity estimates from flawed observational studies that used unsuitable data, were poorly designed and/or employed inappropriate statistical methodology. That obscured what should have been a key message from AR5 – that the best observational evidence now points to the climate system being substantially less sensitive to greenhouse gases than previously thought. Secondly, the elevation of computer models over observational evidence. Virtually all the projections of future climate change in AR5 are based on simulations by GCMs despite these being out of line with the best observational evidence.
    In particular, between since the Fourth Assessment Report of 2007 (AR4) and AR5, there has been a major reduction in the IPCC’s best estimate of how strong the effect – the ‘forcing’ – of atmospheric pollution (aerosols) is. This reduction results from improved understanding and incorporation of observations from satellite-based instruments; in AR4 the estimate was based primarily on GCMs. The reduction necessarily means that estimates of climate sensitivity should be lower too
    .
    Last edited by Iarmuid; 7th January 2014 at 12:38 PM.
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  10. #35010
    Iarmuid Iarmuid is offline
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    For anyone wondering why Climate prediction is so difficult and the uncertainties so large. From Professor Ted Shepherd, Grantham Chair in Climate Science at University of Reading. Happy new year to all btw.

    Last edited by Iarmuid; 7th January 2014 at 12:59 PM.
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