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The year Trump was elected was so hot, it was one-in-a-million

Posted on 11 August 2017 by dana1981

20142015, and 2016 each broke the global temperature record. A new study led by climate scientist Michael Mann just published in Geophysical Research Letters used climate model simulations to examine the odds that these records would have been set in a world with and without human-caused global warming. In model simulations without a human climate influence, the authors concluded:

  • There’s a one-in-a-million chance that 2014, 2015, and 2016 would each have been as hot as they were if only natural factors were at play.
  • There’s a one-in-10,000 chance that 2014, 2015, and 2016 would all have been record-breaking hot years.
  • There’s a less than 0.5% chance of three consecutive record-breaking years happening at any time since 2000.
  • There’s a 0.1%–0.2% chance of 2016 being the hottest on record.

To put those numbers in perspective, you have about a one-in-3,000 (0.03%) chance of being struck by lightning in your lifetime. You have about as much chance of being struck by lightning this year as 2014, 2015, and 2016 each being as hot as they were due solely to natural effects. That means denying human-caused global warming is like planning to be struck by lightning three years in a row. Perhaps a tinfoil hat will help.

On the other hand, in model simulations accounting for human-caused global warming, the odds of these events goes up substantially:

  • There’s a 1–3% chance that 2014, 2015, and 2016 would each have been record-breaking hot years.
  • There’s a 6–12% chance that 2014, 2015, and 2016 would be the three hottest years on record.
  • There’s a 30–50% chance of three consecutive record-breaking years happening at any time since 2000.
  • There’s a 20–27% chance of 2016 being the hottest on record.

It’s unusual to have three consecutive record-breaking years even with the aid of global warming, but without the human climate influence, it simply wouldn’t happen.

Denial from the Trump admin and UK allies

These findings tie in to the “leaked” the National Climate Assessment report, which climate scientists sent to the New York Times for fear that the Trump administration would censor or suppress the document. Previous drafts of the report were available to the public, although few take notice before the final version is published. Climate scientists worried that the administration would tamper with that final version. Among the report’s conclusions:

Many lines of evidence demonstrate that it is extremely likely [95%–100% confidence] that human influence has been the dominant cause of the observed warming since the mid-20th century … the likely range of the human contribution to the global mean temperature increase over the period 1951–2000 is … 92%–123%.

This conclusion is consistent with the latest IPCC report, which likewise concluded that humans are responsible for all of the global warming since 1951. These conclusions are denied by many members of the Trump administration. For example, Trump’s EPA administrator Scott Pruitt said earlier this year:

I would not agree that [CO2] is a primary contributor to the global warming that we see.

Similarly, when Trump’s Department of Energy secretary Rick Perry was confronted with the 100% human contribution to global warming since 1951, he responded by saying “I don’t believe that ... don’t buy it.”

And of course the president himself has called global warming a Chinese hoax, and didn’t mention science once in his shameful speech declaring his intent to withdraw America from the Paris international climate agreement

Across the pond, serial climate misinformer Nigel Lawson recently went on BBC Radio 4 and claimed that global temperatures have declined during the past 10 years. That, of course, is patently absurd considering the record-breaking temperatures we’ve experienced over the past 3+ years. In fact, the short-term warming trend over the past 10 years is higher than the long-term trend.

Scientists were rightly appalled that the BBC once again made the “ignorant and irresponsible” decision to host a climate science denier.

Censorship isn’t the problem – denial is

It’s understandable that climate scientists would worry about the possibility that the Trump administration would censor their findings. Not only has the administration denied this politically-inconvenient science, but the Republican Party has a history of censoring climate science research. That’s what the George W Bush administration did just a decade ago. And the Trump administration has been telling government scientists not to use the phrase “climate change” and deleting climate science information from government websites.

At the American Geophysical Union conference (the largest annual meeting of climate scientists) last December, climate scientists expressed fears about this type of censorship. Many took to the streets to stand up for science. The scientists pledged to have learned the lessons of the Bush administration censorship, and not to allow the Trump administration to do the same. That’s why the National Climate Assessment report was sent to the New York Times. This time, climate scientists are fighting back against censorship of their science.

Unfortunately, scientific censorship is no longer our main concern.

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Comments 1 to 4:

  1. "Unfortunately, scientific censorship is no longer our main concern."

    Agreed, I would suggest general apathy and passivity among the leftie liberal types, and a faith-based determination not to hear a thing or learn a dang thing among the angry right wingers - our our main problem.

    It even seems that SkS comments are not near as active and vibrant as they were not too long ago.  Burn out and preoccupation with one's own life - does not bode well for our future.  I cry for our children.

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  2. I would rephrase this statement:

    "There’s a 0.1%–0.2% chance of 2016 being the hottest on record."

    to clarify that the likelihood or probability that the year was the hottest on record could occur as a result of extremes in natural variation is very low, i.e., 1- or 2-in-1000 or 0.1 or 0.2X%.  Otherwise, the statement reads like there is only a low percentage that 2016 was the hottest year on record.

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  3. If the climate models are rerun with the nonlinear forcing function for carbon dioxide with the centennial resonance obtained by the harmonic sensitivity analysis of climate model output, do the individual probabilities that 2014, 2015 and 2016 would be the hottest on record increase or decrease?  ... those three years consecutively?

    "Slow climate mode reconciles historical and model-based estimates of climate sensitivity

    Cristian Proistosescu* and Peter J. Huybers
    Science Advances 05 Jul 2017:
    Vol. 3, no. 7, e1602821


    The latest Intergovernmental Panel on Climate Change Assessment Report widened the equilibrium climate sensitivity (ECS) range from 2° to 4.5°C to an updated range of 1.5° to 4.5°C in order to account for the lack of consensus between estimates based on models and historical observations. The historical ECS estimates range from 1.5° to 3°C and are derived assuming a linear radiative response to warming. A Bayesian methodology applied to 24 models, however, documents curvature in the radiative response to warming from an evolving contribution of interannual to centennial modes of radiative response. Centennial modes display stronger amplifying feedbacks and ultimately contribute 28 to 68% (90% credible interval) of equilibrium warming, yet they comprise only 1 to 7% of current warming. Accounting for these unresolved centennial contributions brings historical records into agreement with model-derived ECS estimates."

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    Moderator Response:

    [PS] See a realclimate write up here.

  4. citizenschallenge@1,

    I blame the ease of impressing people who are tempted to like to hear support for their desired beliefs regarding the actions they want to personally benefit from.

    And I think that people who call 'other people who govern themselves by rational consideration of how their actions may negatively impact others, and try to get others to also be more sensibly reason-based considerate people' lefty-liberals are a part of the problem, part of the groups of people that need to have their minds changed or be disappointed by being kept from believeing what they want and doing as they please (and the history of action by groups claiming to be Uniting the Right or Conservatives are clearly more unhelpful than the Left or Liberal groups - the many actions of the current winners of leadership in the USA regarding assistance to the least fortunate and action to reduce the harm done to future generations by climate change caused by allowing careless-carefree people to believe and do as they please are more than ample proof of that.)

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