Sunday, July 29, 2012

Climate Extremists

On March 11, 2011 a wall of water, reaching 130 ft high in places, struck the Japanese coast causing extraordinary devastation, including nd extensive damage to the Fukashima nuclear power plant.

Should we blame this disaster on global warming? 

Certainly, the warming of the earth, caused by both natural and greenhouse gas forcing, has caused sea level to rise, with increases of about 10 cm (4 inches) since 1970, roughly when human greenhouse gas forcing became significant.


The answer to the question above is clear: human-caused greenhouse warming may have added a few inches to the height of the water surface, but the great tsunami was caused by an extraordinary natural phenomenon (the Tohoku earthquake), and the impact of sea level rise was really in the noise level.

The reason I mention this example, is that a number of folks are twisting essentially the same situation, but in the atmosphere, to make the case that global warming is making the weather more extreme.  They cite the latest weather/climate disasters as proof:  the current heat wave/drought in the Midwest, the Russian Heat Wave of 2010, the Hurricane Katrina in 2005, the list is endless.  And headline-thirsty media are happy to amplify this message, to the detriment of their readership.


So what is causing the big weather events we are experiencing?   The most frequent reason is an amplification and locking of the upper level flow pattern that controls the weather.  Most of you know about the jet stream, the current of strong winds in the upper troposphere, a feature associated with storms in the midlatitudes.  The jet stream and upper level flow generally has undulations, with troughs  (when the jet stream moves south) associated with cool, wet weather and ridges (when the jet stream moves northward) associated with warm dry weather.  In fact, there are two jet streams:  one in the midlatitudes and one in the subtropics (see picture)

We often show the upper-level flow patterns by displaying the height of pressure surfaces in the atmosphere, often 500 hPa (see below).  You can see the troughs and ridges on this chart (trough lines indicated by dashes).  Now much of the time the troughs and ridges move through (generally from the west to the east) and we get "normal" weather... sunny days interuupted by cloudy, rainy ones (or snowy in winter).  The figure show such a situation.


But sometimes the atmosphere "locks up", with a ridges or troughs staying in one location and increasing in amplitude.  This  locking up is often termed blocking.  Blocking is not well understood, sometimes we can figure out why it is happening, but often we are clueless.  In fact, blocking can happen quite naturally as part of the non-linear, complex physics of the atmosphere.

Many of the extreme weather situations are associated with such locking of the atmosphere.  Why has the middle of the U.S. experienced apersistent heat/drought and the West Coast has been cool and wet?   You guessed it--the upper flow pattern has been locked in a configuration of a ridge over the central U.S. and troughs along the coasts. Here is a sample of the pattern from late June.


Take a look at the departure of the average temperatures from normal for June and the last two weeks when this configuration has been in place.  You see that some of the differences from normal (the anomalies) exceed 9F!.



These are very large anomalies, and FAR exceed that signal that  thescientific community believes might be associated with human-caused global warming over the past 50 years (perhaps 1 F).

You see how this is like the Japan tsunami?  Sure, global warming might be making things a bit warmer, but these major weather/climate events are clearly associated with natural variability.   Global warming...and particularly warming caused by humans...plays a VERY minor role.   This conclusion, for the current heat wve and other events like the Russian heat wave,  is supported by a number of scientific reports, including some very well known scientists at NOAA (an example here).

Now, some of you may ask, could global warming due to human greenhouse gas emission be increasing the amplitude and "locking"  of the upper waves?  There is absolutely no evidence of this.   Some climate model studies, suggest the opposite....that blocking and weather anomalies might DECLINE as the earth warms (see article here that discusses this issue).  So the weather might get LESS extreme.  Other models indicate a slight increase in blocking.  

There is little doubt the earth is warming from a combination of natural and human-induced effects and that the number of high temperature records are being broken as a result (and as result of urbanizaton and poor instrument siting).  But the evidence suggests that  the big weather/climate events have little to do with global warming.

Reading the media and scanning the press releases of environmental advocacy groups, you would not come to these conclusions.   Some organizations, like Climate Central and extremists like Bill McGibben,  hype every major weather anomaly as proof of the profound effects of human-induced global warming.  They ask you to "connect the dots"  but are playing a very unhealthy role in this issue by providing false information.  The trouble is that the media feeds upon this stuff...and my local paper..the Seattle Times....is one of the worst.  Even more embarrassing, national pundits with little climate or meteorological knowledge...like Paul Krugman...are parroting these unproven ideas.

I really appreciate Paul Krugman, but this is really embarrassing for him
The psychology of those hyping extremes is worthy of study and analysis...but I suspect the reasons are clear.  Many are convinced, as they should be, that mankind will have a large impact on the climate of the planet by the end of the century because of our enhancement of greenhouse gases.  Plus, acidification of the oceans.  They believe by hyping the relatively small impacts during the past few decades that they can motivate people to act.  A lie for a good cause.    And yes there is the human side--folks love attention and feeling important...and the media is happy to provide this for those telling tall tales of huge current impacts.
          
I know that a few will jump on me about not mentioning the deceptions of the "other side."  And they are legion.  There is whole climate change denial lobby... funded by energy firms, the Koch brothers, and others... and supported by large group of folks that believe that conservatism and conservation are not compatible, saying that greenhouse gas impacts are an unproven theory, and that natural variability is the only game in town.  They are wrong.   The science is clear: human-induced warming will be a profoundly serious issue for our civilisation by the end of the century.  And the polititicizaiton of this scientifc issue has become very unproductive.

If you believe in the seriousness of global warming in the future, it is essential to stick to the truth.  Over-the-top claims--which are easily provable to be false or which will fail to materialize in the near future-- simply undermine the credibility of the science. Mankind can only make the right decisions if they know the truth...and the uncertainties, and there are two groups in this conversation that are doing much to prevent the public from understanding the nature of this serious problem. 


41 comments:

Fetlock said...

Dr. Mass, I believe that you're right that global warming doesn't justify hyped stories and all of that, but I have to wonder what will happen due to the repeated drumbeat of "we can't predict, we don't know, those who are preaching doomsday are all just out to get attention..." from respected scientists.

Krugman does have a point about we are notoriously inept at seeing past our immediate experience. Very few of us have had the kind of rigorous instruction that you have had in statistics and science. That's why we look to you for guidance.

Ignoring scary articles might be the right thing to do, but what ELSE do you think is the right thing to do? I think a person who is as gifted as you are at public relations does bear some responsibility here. People will look to you for answers. What do you believe we SHOULD we be doing besides ignoring the hype?

chrisale said...

Fetlock:

I couldn't have said it better.

Yes. We must avoid sensationalism but facts are facts. There will be higher temperatures in the future. There will be an unknown effect on both 'the weather' and 'the climate'. The sea levels will increase. The Arctic ice cap will disappear in summer.

We know that there is a time-lag. Stuff we burn/put into the atmosphere today will affect us in the future.

So how do we get that message out there?

I must take issue with this statement though:

"There is little doubt the earth is warming from a combination of natural and human-induced effects and that the number of high temperature records are being broken as a result (and as result of urbanizaton and poor instrument siting)."

If you look at the Berkeley Earth Study, urbanization and poor instrument siting do Not negate the overall signal of a warming planet. They say not only can we be absolutely sure the last 50 years of warming is human caused, but now the last 150 before then too. Do you disagree? (I know you likely have not seen the data yet since it has not yet been published)

"But the evidence suggests that the big weather/climate events have little to do with global warming."

I think that is a poor choice of words.

I would say that the evidence suggests that global warming is currently adding a small part to the big weather/climate events occuring today but that that addition is not only expected to grow but accelerate with business as usual.

Cliff Mass Weather Blog said...

Fetlock and Chrisale,
There are many ways we act now. A few that come to mind:

1. Support research into economic technologies for producing renewable energy.

2. Support climate research to secure a better idea of what will happen.

3. Secure a carbon tax that will push the economy in the right direction.

4. Put more emphasis on economically reasonable conservation (better insulation, etc).

5. Improve the fuel economy of our cars.

and much more. The nice thing is that we should be doing the right thing for many reasons...not just global warming issues.

Keith said...

You can't say "But the evidence suggests that the big weather/climate events have little to do with global warming." You can say "we don't have the evidence to point to whether these events are due to natural variability or whether they are effected by climate change". But you can't discount (or support) any factor which is real when looking a small number of data points.

accretion said...

Cliff:
If you love Paul Krugman, then you ain't a scientist. Paul is a leftist economic hack of the most nasty kind, with zero objectivity. Question: was the world warmer in the middle ages when the Vikings grew grapes in Greenland?!

Cliff Mass Weather Blog said...

Keith...there are a huge number of data points...extreme weather is always happening somewhere and always has!..cliff

Fixed Carbon said...

Cliff: You are obsessed with false positives, as I have pointed out before. You ignore the risk of false negatives. Tell us why you think that global warming is a problem for the future but not for now. I'm beginning to think that you are not an objective scientist. Please convince us of your objectivity.

franzamador said...

I've heard so often that warming is predicted to increase severe weather that I'm really surprised to hear you say it's not. Is that really something that people just made up?

Cliff Mass Weather Blog said...

Fixed Carbon,
Please no personal remarks. The key fact you need to consider is that the greenhouse gas warming "signal" will increase in time as the gas concentrations increase and the thermal mass of the oceans and atmosphere catch up. Right now the signal is relatively small compared to natural variability, but that will change in the future...ciff

Dan McShane said...

It appears that there is some debate as to the frequency of extreme events increasing due to CO2 and an overall warming of the atmosphere. The loaded dice idea on extreme events has been around for a long while now. Given the data of measurable warming, it would seem that this theory is gaining some credibility, but the next generation will know more as our great atmospheric experiment continues.
I did not think Krugman was over the top alarmist and would suggest your reading more into his column based on a reaction to his being in the more extreme events camp from overall warming - a group that includes a fair number of peer reviewed climatalogists. I would note that Krugman clearly indicated that overall warming thus far has been small.
That said I am with you on some of the more ridiculous links to climate cahnge that are routinely made, but I find the complete denial much more problematic.

Cliff Mass Weather Blog said...

Mr. McShane,
An example of a completely unsupportable statement in Krugman's op-ed piece is:

"even a fairly modest rise in average temperatures translates into a much higher frequency of extreme events — like the devastating drought now gripping America’s heartland"
This is simply not true.

My essential point is over-the-top claims is HELPING the denial crowd. It gives them a tool to destroy the credibility of the real science...cliff

Unknown said...

Correction Cliff,
We don't know if it's true yet.

I am among those who think that more heat and energy in the atmosphere results in more blocking/rosby wave activity.

The earth is very proficient in moving heat from its equator to the poles,and the more of it the blocking patterns tend to occur.

As for the denier crowd, their arguments aren't scientific, logical or credible.

The discussion of "loaded dice" and increased heat waves is not outlandish, and far,far more productive than the. Denial tripe repeated en mass all over the Internet.

franzamador said...

Speaking of Bill McKibben, any chance you could do a post responding to his Rolling Stone piece? He's got actual numbers in there that ought to be amenable to rational evaluation.

http://www.rollingstone.com/politics/news/global-warmings-terrifying-new-math-20120719

Jeff said...

One thing I'd be wary of is hiding behind the curtain of extreme objectivity. The truth is that we are not that great at explaining and predicting climate patterns even without the added uncertainty of greenhouse gasses. The danger is that the objective scientist will see all this uncertainty and conclude that we can say nothing about causation. It seems that with the current drought, it is reasonable to conclude that we are uncertain of the absolute causes, but that we would expect it to be hotter than similar droughts in the past.

Glenn said...

Dr. Mass,

I'd appreciate your comments on the paper by Francis and Vavrus in April, connecting extreme weather events with Arctic warming. Specifically, the effect of reduced temperature differential on the movement, or lack of movement, of the Rossby waves in the Polar Jet, and the reduction in the speed of the jet.

Thanks,

Glenn Woodbury

Cliff Mass Weather Blog said...

Unknown,
Yes..the truth is that we don't know about the blocking amplitude under global warming...there is consensus on this issue. What I am saying is that we cannot ASSUME that extremes will be greater under GW...it could be just the opposite for some regions or phenomena. Another example deals with the jet stream. If it moves northward, portions of the west coast could have LESS extreme weather (e.g., windstorms, flooding).
Just have to be careful and admit what you don't know and what isn't a sure thing...cliff

RLL said...

Obvously there is spectrum of credible weather scientists regarding the seriousness of what is happening. Questions I would have:

At the current level of CO2, approaching 400ppm, where will earth's ocean and surface temperature stabilize?

At current trends of CO2 emissions we likely will be hitting 450, 500, even 1000 in the decades ahead. What will temperatures stabilize at those ppms??

Some climate scientists say that 2 degrees centigrade are a tipping point. Should we disregard them?

Others say that we may hit 4-6 degrees centigrade by the end of this century. What are this implications of these temperature rises?

Unknown said...

There may not be scientific consensus on the slowing Rossby wave theory. But there is SOME evidence (e.g. Francis and Vavrus 2012), so when you say "there is absolutely no evidence" you commit the same sin you accuse others of. (Or if we ask those researchers if they think there is "no evidence" do you think they'd agree? Or are they extremists too?)

As to be expected at this point, the evidence is weak and tentative, but the researchers deserve credit in my book for putting forth an interesting theory. Note the evidence comes from real world observations, not models. It links to the melting of the arctic sea ice, which has exposed much more ocean surface to the atmosphere at certain times of the year.

Anyway, back to the issue of consensus. It's pretty clear that almost all climatologists and atmospheric scientists accept the world is warming due to anthropogenic causes, Cliff included. But within that consensus there is a range of opinion on how fast it will occur and whether we can observe significant effects already.

If I'm reading you right Cliff, you think the media should wait until consensus forms around these individual issues (e.g. increased extremes...or not) before publicizing them. My question to you: what if that's too late?

--Douglas

JeffB said...

It is always about prioritization. Especially in tough economic times. As I said in the other thread re: Texas Tall Tales. 100 year timelines are not cause for alarm. They are cause for low priority changes that we can, and will make over time. It is easily conceivable that we would move our entire energy infrastructure to non-carbon sources over the next 100 years. Thorium would easily make that possible. And this would be a great example of reasonable changes that would address the future without hurting us today.

But as long as we continue with the Chicken Little's like Krugman who know nothing about science, we are going to get further from any solutions, and instead hurt ourselves badly today. And especially when the interests of most of the current CAGW groups is more in line with continuing their own funding and influence and/or a remake of the economic system towards more socialism based on immediate alarming predictions about CAGW. Sadly, many in the CAGW camp want us to suffer with Draconian policy as punishment for the growth and triumph of Western Civ over the past 500 years.

Cliff is one of the lone voices of sanity. Let's stick to the science and let real scientists and engineers create new solutions for the next 100 years instead of panicking now.

JeffB said...

And then there is this new paper which shows that warming has been vastly overstated by improper siting of the US Thermometer (USHCN) network.

And again, alarm and reaction to data are entirely dependent on magnitude. As Cliff mentions here, a sea level rise of 4 cm over the course of decades is not cause for alarm, because it is not cause action. No one will have to move property, or flee to higher ground over 4 cm within the noise margin. ALARM means ALARM. MAGNITUDE MATTERS. There is no cause for CAGW alarm, therefore all of our response should be long term scientific research and engineering that seeks better energy solutions, better cars, etc. and not immediate economy destroying panic.

And I very much disagree with a carbon tax as one of Cliff's proposed solutions. We would be far better continuing with the science. I don't understand how Cliff could simultaneously suggest restraint, good science, more understanding, better research into energy sources and better autos, etc. and then mention a carbon tax. That falls under the heading of economy destroying panic. Why not instead incentivize new energy sources like Thorium.

One thing the socialists never seem to understand is that humans react much more vigorously to the carrot than the stick. Ironic for a group that also understands why we should not use torture.

JeffB said...

Unknown asks "What if it is too late?"

There is an obvious answer to this question. It is not. Too late would be if say Puyallup failed to install Lahar monitors and a massive Lahar was bearing down from Mt. Rainier. 4cm sea level rise over 30 years within a noise margin is something buried in scientific papers with absolutely zero implication for the average Puget Sound resident.

MAGNITUDE MATTERS.

Unknown said...

Cliff, you are guilty of the reverse. Your blog post makes it sound like there's no need to be alarmed at all, but your last comment you admit that you simply have no idea about the effect of climate change on the blocking amplitude.


The thing to lose sleep over isn't Krugman making the occasional climate post. The thing to lose sleep over is that if climate change is resulting in increased blocking (even though we can't prove it), then that means that the negative effects of climate change are here right now, and that means that they're going to be worse than most predictions to date. I'm not willing to bet that this is just weather and that it doesn't require a response and that magically the weather extremes of the past 2-3 years will simply abate by themselves.

Unknown said...

The Tsunami reached heights in excess of 9 meters (900cm) near Fukushima. So sea level rise of 10 cm may have contributed a bit more than 1% of that height.

In contrast, using your conservative 1 F increase estimate for AGW, global warming may have contributed to 10% of the current drought, using your 9F anomaly figure. An order of magnitude difference in other words.

If the BEST results are to believed however, humans have contributed to about a 2.7 F degree rise in the past 250 years. That means we might have made the current drought 30% worse!

I realize this is a simplistic analysis, but your example is not well chosen.

--Douglas

caveat emptor said...

Cliff you say that this is unsupportable

"even a fairly modest rise in average temperatures translates into a much higher frequency of extreme events ....."

However that is a simple property of most statistical distributions. If you increase the mean, then you increase the probability of events over certain thresholds occuring. For very extreme events the increas in probability is significant especially if their is a sizeable shift in the mean.

JeffB said...

Unknown says:
I'm not willing to bet that this is just weather and that it doesn't require a response and that magically the weather extremes of the past 2-3 years will simply abate by themselves.

This is nonsense. There are weather extremes at all times somewhere on the planet. If we use a bet on weather extremes as a reason for gross action, we may as well use a roulette wheel.

strix27 said...

I think we're getting tied up in knots over the details rather than the basic physics and chemistry of Global Climate Change, and not just "Global Warming." The CO2 in the atmosphere is increasing at an unprecedented rate, baring the extreme geological/volcanic events like the formation of the Deccan Traps.

Part of the CO2 is entering the oceans increasing its acidity. The remainder is increasing both the heat in the atmosphere and the oceans. Water has a very high heat capacity, so the sea surface temperature (SST) is warming slowly. But that slow warming is increasing the water content of the atmosphere, which helps to slow the rate of increase of SST.

Increased atmospheric heat and humidity appear to have altered atmospheric circulation and increased the severity and frequency extreme meteorological events since the beginning of the industriall revolution (nominally in 1800, but actually much earlier.) There s statistical evidence to support this contention, but we're looking at only 200 years of record.

However, the rate of increase in frequency of extreme events is worth noting and in some cases unprecedented, in human history. Little ice ages and climatic ameliorations have occurred on longer time scales and with less severity than now.

The benefits of industrialized civilization finally accruing over such a seeminly short period of time forbids suddenly putting on the brakes. This process is akin to historic cyclic economic boom and busts in which there is always reaction instead of prevention.

I think Bill McKibben's essay in Rolling Stone is very compelling.

richard583 said...

With all of what you've said here above Prof. Mass, (if perhaps fairly obvious.) .. it would appear, that actually identifying / determining the key factors involved more specifically where considering just what causes the more "locked" up state /- or either otherwise, move freed up movement, of the main progress of the atmosphere more eastward as a whole, would also perhaps help, where looking at the gradual warming of the climate. ..

Ferdi said...

While climate alarmists may or may not be a serious distraction, the real climate extremists are those that deny humans are having any affect on the climate at all, or even deny there is any global warming taking place. These people are by far the larger impediment to enacting measures to mitigate humankind's affect on the atmosphere.

Unknown said...

JeffB, of course there are extremes all the time. But are they becoming more frequent, and more extreme? This is the nub of the issue. Some scientists say yes (Cliff strangely doesn't mention Hansen), others think no for now at least.

I have a hard time parsing the rest of what you say. Most of it seems like talking points from Rush or Drudge. Advocating a carbon tax or other measures is not necessarily "economy destroying" and could in fact benefit the economy (by stimulating important industries) rather than hampering it. Note a popular idea is a revenue neutral carbon tax, i.e. one that is offset by tax cuts elsewhere.

I did not say it is too late NOW. I meant in 10 years or however long it takes for scientists to reach consensus on AGW impacts on extreme events.

--Douglas

Branden said...

JeffB, please don't link an non-peer-reviewed paper from WattsUpWithThat, one of the most public, if not the most public, denialist sites on the internet.

Dan McShane said...

Is it possible to describe the recent warming in the Arctic as extreme? If so, is it possible to link that extreme Arctic warming to CO2 forcing? Or is that being extreme?
All and all an interesting dialog that really revolves not around anthropogenic climate change, but around how to advance policy and the strategy to do that. I will say that I may disagree with the strategy some use by citing EVERY storm or weather event, I do not find it helpful to call them extremists in converstaion or elsewhere.

Brendan said...

@ JeffB

A carbon tax would incentivize new energy sources (like thorium). That is the purpose of a carbon tax.

JeffB said...

Unknown,
But you are simply wrong. There have not been recent more frequent and more extreme weather phenomena. You are an unfortunate victim of the 24/7 media culture that sensationalizes each tornado, drought, hurricane, etc. See links below for starters. And this is not about Rush or Drudge. I don't pay attention to either. Alarm is not a partisan issue.

And again, even you retract your statement to say that too late actually means ten years from now. Think about the ridiculousness of that verbiage.

There is either real, meaningful, quantifiable, objective, measurable, predictable and empirically demonstrated cause for alarm, or there is not. And when there is alarm, all of those measures above are easily verifiable in the here and now.

If you have to retract and say you meant it might be too late in ten years, then it's not too late, and that's not anywhere near accurate enough to cause anyone to take action and certainly not cause for alarm.

I don't see why you are surprised that public opinion is not swayed by all of the climate hysteria of that last few decades which for the average Joe has amounted to nothing more than the usual weather. And that's Cliff's point. You want to sell hysteria like the hurricane images of Al Gore's movie posters did as a call for action. But in reality, hurricanes come and go, and have been no more frequent of late. And the consistent cries of alarm when there is none have deadened everyone.

Thankfully, there are people like Cliff who are calling for reason to triumph over emotion.

http://www.worldclimatereport.com/index.php/2012/07/13/the-heat-was-on-before-urbanization-and-greenhouse-gases/

http://pielkeclimatesci.wordpress.com/2010/06/08/guest-post-by-bruce-hall/

http://notrickszone.com/2012/05/25/comprehensive-alps-study-clearly-refutes-humans-are-causing-more-weather-variability-and-extremes/

JeffB said...

Branden,

Why? Are you afraid you might read something there that contradicts what you had accepted as fact? And what of all of the peer reviewed papers linked to that site? Are you saying that negates their peer review?

JeffB said...

Brendan,

There are many ways to incentivize new energy. One is to tax what you don't want. Another is to credit or encourage what you do want. Humans work better with encouragement. And especially when we are talking about something as critical as energy. Punishing us all for the energy sources we have now is not productive, because most would certainly prefer less of the bad effects of burning carbon, but more importantly, they need the energy from those sources we use now to survive. This is why we don't tax food.

A better way would be to encourage an Ansari X prize like incentive, and to get the US Gov to go back and open up all of the research and closed pathways to Thorium that previously existed.

And we did not take flight by taxing trains.

Unknown said...

Jeff B, you deliberately try to twist my words. Nothing has been retracted. I said:
"If I'm reading you right Cliff, you think the media should wait until consensus forms around these individual issues (e.g. increased extremes...or not) before publicizing them. My question to you: what if THAT's too late?"

See the word "THAT"?...clearly it refers to a point in the future when there is a consensus re extreme events. It could be 5, 10, 20 years("in 10 years or however long")...I don't have a crystal ball.

"But you are simply wrong. There have not been recent more frequent and more extreme weather phenomena."

And I can link to many other peer reviewed papers that say the opposite to some degree. However I would NOT make a blanket statement like you have, that there HAS definitely been an increase in extreme events. I'm agnostic for now, and open to evidence both ways. (I appreciated Cliff's post on the Texas drought paper).

However, I believe there are prudent measures we can take now (e.g. carbon tax) before we have consensus on how extreme things will get and how soon. Because, unlike you, I don't think these will "destroy the economy" -- if anything they'll help.

--Douglas

Keith said...

Professor Mass,
With respect, you stated "But the evidence suggests that  the big weather/climate events have little to do with global warming". What is your confidence interval for this conclusion? Your chart showed a great degree of variability, true, but it also showed a measurable, separable component that is exclusively due to CO2 in the atmosphere. This is why I take issue with such a strong statement as you have made. I respectfully request in the future a more rigorous statistical analysis, or statement at least, supporting such controversial positions.
Best regards

Eric said...

What's missing in this discussion is the difference between the impacts of radiative forcing on the variability (that is, the underlying atmospheric dynamics) and the impact on mean temperatures, upon which the dynamics is superimposed. Cliff is right that there is no evidence to support the assumption that global warming will itself lead to "more extreme weather", if by that we mean dynamical events like the atmosphere blocking like that which resulted in the Moscow warming extreme. However, if average temperatures are overall greater, the the changes of a given weather event being hotter than previous ones increases. At the moment, as Cliff says, the statistics are such that the signal of that warming barely rises above the noise of natural variability -- for example, a paper in PNAS last year concluded that the probability was about 80% that the Moscow warming was exacerbated by the long term (global warming) trend. See: http://www.pnas.org/content/early/2011/10/18/1101766108.abstract

80% probability isn't very high, and in fact would usually be rejected as "insufficient evidence" for most scientific studies. On the other hand, we know where the trend is heading.

Of course, the heat wave in France in 2003 is another matter. This is the one event which is the counterexample to Cliff's otherwise right-on post. See the paper in Nature on this, here: http://www.nature.com/nature/journal/v432/n7017/abs/nature03089.html

--Eric Steig

zorch said...

Cliff- Why are you accusing the press of promoting hysteria when the head GW scientist at NASA is the one fanning the flames?


http://www.latimes.com/news/science/sciencenow/la-sci-sn-extreme-summer-heat-climate-change-scientists-say-20120806,0,7931870.story?Sdsdfsd

Bill said...

Dr. Mass, I'm interested in your opinions on the recent PNAS paper regarding a statistical argument that extreme weather is in fact increasing. "Perception of climate change." by James Hansen, Makiko Sato, and Reto Ruedy.
I am no expert in this field, but it seemed to me the authors did a laudable job of sticking to facts and showing that the incidence of extreme weather has in fact been steadily increasing over the last 50 years.
Fortunately for us, it is open access as well. http://www.pnas.org/content/early/2012/07/30/1205276109.abstract

-Bill

Paul Vincelli said...

Dr. Mass, I would like to understand better your objections to the Krugman statement, "even a fairly modest rise in average temperatures translates into a much higher frequency of extreme events — like the devastating drought now gripping America’s heartland". As caveat emptor points out above, the first phrase is supported by virtue of it being a property of the normal distribution, and it is reflected in Figure 4 of Hansen’s latest PNAS paper. The second phrase is not a direct attribution, merely pointing to the drought as exemplary. I really would like to read your arguments on these points, because Krugman’s phrasing seems defensible, and before I say the same things as an educator, I would like to read your thoughts on what is problematic about these points. Thanks for your time.