Climate

Must-See Video: Has Global Warming Caused A Quantum Jump In Extreme Weather?

“The climate has shifted to a new state capable of delivering rare & unprecedented weather events,” explained Weather Underground director of meteorology and former hurricane hunter, Dr. Jeff Masters.

Increasingly, scientists and meteorologists are asking whether global warming is driving a quantum jump — a non-linear shift — in our extreme weather.

We now have enough observations and analyses that a scientific literature on this subject has begun to emerge:

This is not your father’s climate, as Stu Ostro, senior director of weather communications at the Weather Channel has documented at great length (see this big PDF)

Peter Sinclair has put together an excellent video for the Yale Forum on why even the modest 1°C warming we’ve seen over the past century can cause a disproportionally large shift in our weather systems:

RealClimate ran an excellent, semi-technical explanation by Stefan Rahmstorf and Dim Coumou of Germany’s Potsdam Institute for Climate Impact Research. They explained how global warming sharply increases the likelihood of ‘outlandish’ heat waves (see charts below) and concluded:

So in summary: even in the most simple, linear case of a shift in the normal distribution, the probability for “outlandish” heat records increases greatly due to global warming. But the more outlandish a record is, the more would we suspect that non-linear feedbacks are at play – which could increase their likelihood even more.

Since this is an emerging field, it’s no surprise that not every climate scientist agrees. Martin Hoerling, who heads the “Climate Scene Investigators” at the National Oceanic and Atmospheric Administration, emailed blogger Andy Revkin a statement that included this truly remarkable sentence:

After all, the irony of extreme events is that the larger the magnitude the smaller the fractional contribution by human climate change.

This is the linear view of things: The modest amount of warming that we have had to date can have no more than a modest impact on any extreme event, large or small.

The emerging literature says otherwise. I asked for a comment by two leading climatologists, Michael Mann and Kevin Trenberth.  Here is Mann, director of the Earth System Science Center at Penn State:

Hoerling’s statement hopelessly confuses two very different things, modest shifts in the average, and the dramatic impact those shifts can have on the incidence of extreme events. The anomalous recent U.S. heat is a manifestation of the latter. It is a demonstration of that we have loaded the random weather dice toward producing far more “sixes” than we would expect from chance alone.

UPDATE: Dr. Mann emailed me to clarify that he was using the word hopelessly “simply to indicate that I thought there was no possible justification for the connection that Hoerling was making.” If you read Hoerling’s email slamming Rahmstorf and Coumou, it’s clear that Mann’s statement is very mild in comparison.

And here is Trenberth, former head of the Climate Analysis Section at the US National Center for Atmospheric Research:

When climate changes, the percentage changes in frequency are always greatest for some extremes (what are referred to as the tails of the distribution).  No matter how much climate changes, there is always weather and natural variability such as El Nino, and this can be beguiling. Extremes are inherently rare events but natural variability can break records all by itself.  But when the climate has changed, and we know it has, the odds of a particular extreme can easily be magnified many fold: what would be in an unchanging climate a 1 in 1000 or even 1 in 1,000,000 or more event becomes a 1 in 100 year event, as has been documented in some cases.  What were 500 year storms become 50 year storms: still not common but with much amplified odds. So while natural variability plays a key role, the effects are amplified by climate change: when natural variability is moving in the same direction as climate change, we not only break records, we smash them.   And this is what we have seen especially in the past 2 years.

The above are largely statistical statements and climate research is also involved in understanding how these actually come about.  While harder to prove, nonlinear effects often come into play to compound the issues as the accumulated effects of global warming set the stage for amplified responses.  For example the extra heat from global warming dries the land and removes evaporative cooling as an option for the subsequent heat wave.  Or extra moisture triggers instabilities in storms that make them much more severe than otherwise expected.  Yet the phenomena that cause the extremes — thunderstorms, tornadoes, hurricanes, drought, blocking anticyclones — are familiar and it is easy to be led astray and say they are natural. Their effects and impacts are not.

Again, Rahmstorf and Coumou put this well in charts at the end of their post:


IPCC (2001) graph illustrating how a shift and/or widening of a probability distribution of temperatures affects the probability of extremes.

For illustration, let’s take the most simple case of a normal distribution that is shifted towards the warm end by a given amount – say one standard deviation. Then, a moderately extreme temperature that is 2 standard deviations above the mean becomes 4.5 times more likely (see graph below). But a seriously extreme temperature, that is 5 standard deviations above the mean, becomes 90 times more likely! Thus: the same amount of global warming boosts the probability of really extreme events, like the recent US heat wave, far more than it boosts more moderate events.

This is exactly the opposite of the claim that “the greater the extreme, the less global warming has to do with it.” The same is also true if the probability distribution is not shifted but widened by a constant factor. This is easy to show analytically for our math-minded readers.


Graph illustrating how the ratio of the probability of extremes (warmed climate divided by unchanged climate – this increased likelihood factor is shown as a dashed line, scale on right) depends on the value of the extreme.

As Coumou and Rahmstorf concluded in a Nature Climate Change piece,A decade of weather extremes” (subs. req’d):

It is very likely that several of the unprecedented extremes of the past decade would not have occurred without anthropogenic global warming…. The evidence is strong that anthropogenic, unprecedented heat and rainfall extremes are here — and are causing intense human suffering

The really worrisome part is we’ve warmed only about a degree and a half Fahrenheit in the past century. We are on track to warm more than five times times that or more this century (see M.I.T. doubles its 2095 warming projection to 10°F — with 866 ppm and Arctic warming of 20°F ).

In short, Mother Nature is just getting warmed up!

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16 Responses to Must-See Video: Has Global Warming Caused A Quantum Jump In Extreme Weather?

  1. Pangolin says:

    When we look at climate records from Greenland and Antarctic ice cores we see very rapid transitions from one climate state to another. This would imply that the earths climate has stable states but once those states are disrupted the climate can change very rapidly to a hotter or cooler phase.

    Or if it happened quickly before it can happen again.

  2. Mulga Mumblebrain says:

    I seem to recollect James Lovelock or some other worthy saying that, in their opinion, the climate would go through a period of intense instability before jumping to a new, and hotter, steady-state. I assumed that the scenario was one where emissions had peaked, otherwise the process would be repeated over and over. No sign of a reduction in emissions-in fact I can only see the signs of a frantic determination to burn every gram of recoverable hydrocarbons on the planet.

  3. John Tucker says:

    That picture of the house with the extensive earthen works freaks me out. Incidentally I wonder if you left that up after the flood, added a few solar/wind pumps, shade tress, etc.., if you could create a micro climate much cooler in summer than your surroundings.

    Indeed the way its going leaving it up, at least partially might be a good idea as you may need it for the next flood sooner than you would think.

  4. John Tucker says:

    The mean and variance graphs are very helpful as a visual explanation.

    Sobering :

    “the odds of a particular extreme can easily be magnified many fold: what would be in an unchanging climate a 1 in 1000 or even 1 in 1,000,000 or more event becomes a 1 in 100 year event, as has been documented in some cases. What were 500 year storms become 50 year storms: still not common but with much amplified odds.”

  5. Raul M. says:

    Great video, so much said in a few minutes, and such changes in two years.

  6. Mike Roddy says:

    I would like to see this exercise: instead of someone insisting that scientists prove that a weather event is caused by global warming, we should ask someone to model this global weather as natural variability. I wonder what the probability of that is? Low single digits, I would guess.

  7. Or, as a denialist would say, if it happened before, then it can’t be anthropogenic now.

  8. Mulga Mumblebrain says:

    Ask the denialists to produce real science!?? You are asking for a miracle.

  9. Spike says:

    The one positive effect of this statistical quirk is that the substantial increase in extreme events will finally make the penny drop about the reality of the emergency amongst the population at large, provided they occur in the richer parts of the world. There is after all a tendency to ignore climate tragedies visited upon the poor in the third world.

  10. Spike says:

    The Revkin article on this was fairly typical sadly – a long and rather rambling discourse in search of a false balance or middle course. I am reminded of a politician in the UK who described an opponent as “going around the country stirring up apathy”. No wonder Heartland are impressed.

  11. Lionel A says:

    I missed this one from Geoff’s Wunder Blog (due largely to internet going down for hours on end every day), watch the video of a train being derailed – section eight below the wrecked school bus image .

  12. Raul M. says:

    Considering that it is not my fathers weather anymore, are not changer in store for the education of weather and climate? And how long should it Thai for the instructors, teachers and professors to catch up to the changes shown as of this year? And how are they to keep up with the changes as it progresses? Certainly, they won’t like just having a course of “this sure is strange weather”.
    Just asking.

  13. Raul M. says:

    Sorry, should be changes and take for the corrections.

  14. BillM says:

    A visual comes to mind when talking about increasing CO2 in the atmosphere – and therefore heat energy – and its effect on the weather.

    What I imagine is a complete opposite set of conditions. That is, the CO2 is represented by a slope of a constantly increasing angle downward. The weather, a boulder started rolling down it. If the slope were to simply remain on a consistent angle the boulder would still pick up energy and would eventually be bounding wildly.

    But if the slope constantly increases then the boulder picks up energy that much faster and bounds that much more wildly and with that much more force.

    As the boulder bounds, more and more people will be forced to get out of its way. Emigration is the new Noah’s Ark sans the compassion for our fellow creatures.

  15. Mad Max says:

    It’s only going to get worse while we sit here blabbering. We don’t have to live like this.

    Read “Common Sense 3.1” at (http://www.revolution2.osixs.org )
    FIGHT THE CAUSE – NOT THE SYMPTOM

  16. The Oracle says:

    Pangolin said: “This would imply that the earths climate has stable states but once those states are disrupted the climate can change very rapidly to a hotter or cooler phase.

    Or if it happened quickly before it can happen again.”

    About 15 years ago I saw a 1-hour program on Nova or TLC that reported the findings of an international team of scientists who had drilled for ice core samples in the Antarctic, checking on atmospheric conditions dating back before the beginning of the last Great Ice Age and thousands of years earlier.

    They were surprised after checking these Antarctic ice core samples. Before the last Great Ice Age began, there was an atmospheric heat spike (maybe like we’re seeing now, no matter what the reason for the heat spike back then). But what really surprised them was that between when this heat spike occurred and the ice age began, it only took Thirty Years.

    I thought I’d post this because it supports your statement. Of course, scientists in the intervening 15 years or so have done much more research and analysis of ice core samples and other “dating” substances, so I don’t know if this initial study and conclusion from 15 years ago still stands, but it sure got me to thinking back these about how rising atmospheric temperatures might just lead to a surprise, with first the earth heating up and then for some reason the polar ice and glaciers coming back with a vengeance (one theory was that global ocean currents were disrupted between the heat spike of thousands of years ago and the beginning of the Great Ice Age 30 years later). Whatever, we will all have a front row seat.