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Current state of evidence on whether climate change is causing recent extreme weather events
August 13, 2012 2:37 PM   Subscribe

Is climate change causing our recent extreme weather events? (pdf). A panel of eminent climate scientists lays out the current state of what we know, and what we don't know yet, in this forthcoming paper. Jason Samenow (of the Washington Post's Capital Weather Gang blog) nicely summarizes the key points.

The multi-author paper (Kunkel et al) is called "Monitoring and Understanding Trends in Extreme Storms: State of Knowledge", has been peer-reviewed, and is forthcoming in the Bulletin of the American Meteorological Society.

The study's goal: "This paper is meant to present a clear record that can be used by meteorological professionals about what is known and unknown and why."

Samenow's capsule takeaway: For most categories of extreme storms studied, the evidence is not sufficient yet to draw conclusions with any confidence. Extreme precipitation is the only category where the evidence is strong enough.
posted by LobsterMitten (46 comments total) 19 users marked this as a favorite

 
Therefore we, as a nation, still do not need to change anything about the way we live and comsume.

*cranks the a/c down a few more degrees*
posted by Danf at 2:55 PM on August 13, 2012 [1 favorite]


Timbaland_yelling_'Yeah!'_in_the_background_of_'SexyBack'.wav
posted by samofidelis at 2:55 PM on August 13, 2012 [3 favorites]


We'd better wait until we have three or four more decades of evidence before taking any action against climate change.
posted by perhapses at 2:56 PM on August 13, 2012 [7 favorites]


Seemingly there is no reason for these extraordinary intergalactic upsets... Only Doctor Hans Zarkhov, formerly at NASA, has provided any explanation... This morning's unprecedented solar eclipse is no cause for alarm.
posted by Ice Cream Socialist at 2:57 PM on August 13, 2012 [11 favorites]


Science confirms what science-haters knew in their guts-- thus, science is worthless! So is logic.
posted by cell divide at 3:00 PM on August 13, 2012


Can we really be sure? I would need to see a birth certificate...
posted by Damienmce at 3:02 PM on August 13, 2012 [1 favorite]


Yes.
posted by maryr at 3:05 PM on August 13, 2012




Gang, this is not denialism. The scientists are NOT denying that climate change is happening and is bad. They are specifically addressing the question of what evidence we have -- and where we have blank spots, needing more data -- on the effect of large-scale changes (climate changes) are affecting the smaller-scale phenomena (the extreme weather events).
posted by LobsterMitten at 3:13 PM on August 13, 2012 [14 favorites]


I am of the opinion that we're causing some change, and also that the interwebs make it appear that there are way more disturbing disasters than before. So, it's a double-whammy.
posted by jimmythefish at 3:14 PM on August 13, 2012


Sad, but true, rh.

I outside under a tree sipping my strawberry-lime from Sonic last night watching some gal run the engine in her black SUV for over thirty minutes while she and her brood ordered and ate.

It was hot, but shady and pretty nice under my tree.
posted by BlueHorse at 3:18 PM on August 13, 2012


Is climate change causing our recent extreme weather events?

...Let me get this straight -- the question is whether climate change is causing changes in the climate?
posted by EmpressCallipygos at 3:31 PM on August 13, 2012


Climate is not the same as weather.
posted by palbo at 3:34 PM on August 13, 2012 [8 favorites]


Actually the question answered by the paper is whether significant trends are observable in the frequency of storms over the period 1950-present.

It has nothing to do with say, the current drought, or record high temperatures as observed in the first decade of 2010. It also doesn't contradict the recent Hansen paper on that subject, it's grappling with a completely different question.
posted by mek at 3:35 PM on August 13, 2012 [3 favorites]


first decade of the 21st century, whoops.
posted by mek at 3:36 PM on August 13, 2012


The bad news is there is no good news.
posted by tommasz at 3:44 PM on August 13, 2012 [1 favorite]


Climate is the large-scale, long-term.
Weather is the smaller-scale, short-term.

Extreme weather events are things like tornadoes, hurricanes, etc.

The question is, given that climate change is happening, how strong is our evidence that it is causing certain extreme weather events? What additional evidence would we like to collect to get better answers?
posted by LobsterMitten at 3:47 PM on August 13, 2012 [4 favorites]


Seems like good news for non-deniers to me: They are pretty damn certain that climate change is causing one weather extreme: heavy precipitation. So like, Nashville flooding, the spread of disease across the world... Isn't that enough to warrant calling climate change bad enough to take action on? Maybe? Sigh.
posted by Potomac Avenue at 3:58 PM on August 13, 2012 [2 favorites]


Just to underline that the authors are not denialists, an excerpt:
"There is broad recognition that our climate is non-stationary and changing (Global Climate Change Impacts in the US 2009), not only in mean conditions but in its extremes as well (Katz 2010). "

They also say, according to Samenow's summary, that precipitation is where we have the best data sets, and in that domain a trend of increasing severity is clear.
"Reliable data indicate heavy precipitation events are increasing and rising amounts of water vapor in the atmosphere due to human-caused warming offer a good, but not necessarily complete, explanation."

The point of the article is to help meteorologists talk to the public accurately about how strong the evidence of various trends is, and in how strong the evidence for the causes of the trends is. It is definitely NOT aiming to downplay the importance of climate change.
posted by LobsterMitten at 3:59 PM on August 13, 2012 [1 favorite]


To repeat what I said in the recent thread on a very similar topic:
there's some (deliberate?) confusion in what's happening with the weather here. No one is claiming that without climate change the summer would have been completely normal. What is being asserted is that rather than breaking (say) 400 heat records, only 300 would have been. Rather than 2500 counties being drought declared, only 1800 would have been.

We had a 48° day (118° F) in Melbourne in Feb 2009. Without climate change it still would have been an utter stinker, say 45°, it would not have been an average day of 32°. But that 3° still did matter, it made the inevitable bushfires just that much worse.
posted by wilful at 4:02 PM on August 13, 2012 [2 favorites]


I think the aphorism is that weather is like a boxer, climate change is training the boxer to hit harder.
posted by wilful at 4:02 PM on August 13, 2012 [1 favorite]


In more joyous news, the BBC reports Arctic sea ice is vanishing much faster than generally expected, according to preliminary data from European Space Agency satellite Cryosat.

Where once it was thought the Arctic would stay completely frozen over summer until the end of the Century, apparently we might be lucky to make it to the end of the decade.

We're #1.
posted by Mezentian at 4:23 PM on August 13, 2012


So you know that thing, where we have a spot of calm, pleasant weather and the denialists all go SUCK IT SCIENCE? Turns out it's way more depressing when we do it.
posted by Durn Bronzefist at 4:29 PM on August 13, 2012


I'm glad I don't have kids. Manmade, natural, whatever...I don't know how I'd sleep at night.
posted by "But who are the Chefs?" at 4:32 PM on August 13, 2012


Climate is not the same as weather.

Climate is the aggregate of weather.
posted by hippybear at 4:33 PM on August 13, 2012


For crying out loud, allow me to reiterate what the best climate scientists have been saying since forever:

WEATHER DOES NOT EQUAL CLIMATE.

We know that the atmosphere is warmer than it was. We know that temperature increase is caused largely (if not entirely) by humans putting more greenhouse gases into the atmosphere. We know that climate models indicate that there will be more severe weather over a long period of time and that the ocean levels will rise over that period as well (due to more ice melting), and a lot of other nasty consequences, some of which we haven't yet teased out of the various damping/reinforcement mechanisms (i.e. could the stall of the thermohaline conveyor actually rebound global warming into an ice age? perhaps).

What we DO NOT YET know, and it is nearly impossible given the current state of the art to say is that A PARTICULAR EXTREME EVENT (whichever it is) is caused directly by increased global average temperatures (more energy in the atmosphere causing wilder oscillations at both the high and low ends).

What we DO KNOW is that it makes extreme weather events (droughts, floods, heat waves AND cold waves) more likely in certain locations.

What we NOW KNOW based on the latest research (linked above) is that extreme levels of precipitation in recent years are likely caused by increased global temperatures.

Climate Science is a statistics-based field. Discrete events are hard to draw causation -- almost impossible. So don't fall for the denialists' bullshit and start talking as though a single event is due to global climate change. It just plays to their false narrative and loses the statistical basis of the science.
posted by chimaera at 4:39 PM on August 13, 2012 [12 favorites]


Climate is the aggregate of weather.

Yes. Over a whack of time.

I'm not sure where some people got the idea that the Precautionary Principle requires mockery of the continued collection of data as an unwelcome or valueless thing. It doesn't. It isn't. And it makes people look pretty damn partisan and anti-science.
posted by Durn Bronzefist at 4:42 PM on August 13, 2012 [3 favorites]


What we know about climate change and drought (Brad Plumer)

It’s not yet clear whether we’ve reached the point where global warming is making droughts worse again, at least in North America.

Climate models tend to agree that droughts will get more intense and frequent in the Mediterranean, in central North America, Mexico, northeast Brazil and southern Africa, though there are still uncertainties as to exact regions.

posted by Golden Eternity at 4:44 PM on August 13, 2012 [1 favorite]


mek: "Actually the question answered by the paper is whether significant trends are observable in the frequency of storms over the period 1950-present.

It has nothing to do with say, the current drought, or record high temperatures as observed in the first decade of 2010. It also doesn't contradict the recent Hansen paper on that subject, it's grappling with a completely different question.
"

Thank you, mek, this should have been clarified in the OP as it's quite different. It wouldn't hurt to have a mod intervene and change the wording. "frequency of storms" is very different from "recent extreme weather events".
posted by stbalbach at 4:45 PM on August 13, 2012


Furthermore, don't start talking like scientists who say that we don't have enough knowledge to say that specific extreme events are due to global increased average temperatures are denialists.

That belies a major misunderstanding of the very basics of the science.

Like someone who doesn't understand the basics of biology defending evolution causes more harm than good, I don't want you "defending" our understanding of climate change by calling good scientists denialists because you don't get the science they're doing.
posted by chimaera at 4:46 PM on August 13, 2012 [1 favorite]


allow me to reiterate what the best climate scientists have been saying since forever: WEATHER DOES NOT EQUAL CLIMATE.

Except when it does. It is possible to attribute weather events to climate change, this is not some sort of law of the universe, if anything over time we gather more data and expertise our ability to see the footprint of climate in weather gets better.
posted by stbalbach at 4:48 PM on August 13, 2012


Hot seawater forces shutdown of nuclear reactor in Connecticut
..the [Atlantic ocean] has never before been too warm to cool the reactor [before].
posted by stbalbach at 4:51 PM on August 13, 2012 [6 favorites]


I am clear evidence of extreme precipitation.
posted by It's Raining Florence Henderson at 4:59 PM on August 13, 2012 [5 favorites]


You are clear evidence of extreme Wessonality.
posted by hippybear at 5:23 PM on August 13, 2012 [1 favorite]


whether significant trends are observable in the frequency of storms over the period 1950-present.
-mek

This is right - I was going by Samenow's framing, which begins by talking about 2011's extreme weather events (the paper also opens by touching on those) as a reason why the public are asking meteorologists about this.
posted by LobsterMitten at 5:38 PM on August 13, 2012


All the explanation of the meaning of "weather" is sort of anticlimatic.
posted by maryr at 7:15 PM on August 13, 2012


What we have here is a clear case of eponymisnomer. For strong evidence that extreme weather events are due to climate change, refer to the article written by Dr. Windsor Differentnow.
posted by perspicio at 7:25 PM on August 13, 2012


Windsor wins whether her winds wind widdershins or winter's weather withers when Wendy's winds winnow winsome snows from wicked ones. One is wont to want differently, as Dr. Differentnow is the dearest darling of the day, due to her daring dissertation on Differential Dynamics in Dedacal Drought Density and Duration, merited meaty by most meteorologists met immersed in modern measurement methodology.
posted by maryr at 7:53 PM on August 13, 2012


Related post on James Hansen.
posted by homunculus at 8:20 PM on August 13, 2012


Arctic sea ice is vanishing much faster than generally expected, according to preliminary data from European Space Agency satellite Cryosat.

Russia and Canada Gear Up for Arctic Non-War
posted by homunculus at 8:23 PM on August 13, 2012 [1 favorite]


Climate is not the same as weather.
Climate causes weather. That's why they don't have snowstorms in Bermuda and monsoons in the sahara desert (at least not yet)
For crying out loud, allow me to reiterate what the best climate scientists have been saying since forever:
WEATHER DOES NOT EQUAL CLIMATE.
Yeah, I'm not really sure that's exactly what they're saying. Plus "NOT EQUAL" is a rather strong statement. Not equal makes it sound as though there is little interplay, when in reality there is a huge effect. (technically 99.99999x100 isn't equal to 1.00000, but a statement that two things are "not equal" might be interpreted more as that they are orthogonal, i.e. have no impact on each-other)
Climate Science is a statistics-based field. Discrete events are hard to draw causation -- almost impossible. So don't fall for the denialists' bullshit and start talking as though a single event is due to global climate change. It just plays to their false narrative and loses the statistical basis of the science.
I disagree.

If you want to calculate the future state of the weather, one way to use the Navier–Stokes equations. The problem is, it's a non-differentiable equation and so you have to compute it using brute force, so it's basically impossible. And there are tons of other variables like the ocean temperatures and other things.

But in any event, temperature is a parameter in those equations. Change the temperature and you change the result. Over a long term, a world with global warming will have totally different specific weather events then one without (same as with the whole butterfly flapping it's wings thing, except this is a much bigger input)

So really, if you want to be technical, global warming is one of the 'causes' of every weather event, along with everything else that affects the weather (butterflies, etc)

Without global warming, we would have different weather events.

Critically, though the extreme ones would be less common.

Blaming global warming for a specific extreme weather event isn't unscientific (in my view) and has nothing to do with what "denialists" are claiming.

I think two statements are true: 1) "If not for global warming, events like this would have been less likely to occur" and 2) "Therefore, If not for global warming, this probably wouldn't have happened"

It gets tricky because the probability of a known event is 1.0. But what you can say is, if you were to go back in time to before this event was known to occur the probability of something like it happening would be lower without global warming. That's what I mean when I say "this probably wouldn't have happened"
Like someone who doesn't understand the basics of biology defending evolution causes more harm than good
Do you have any evidence that people who don't have a firm grasp on evolution defending it cause problems? I actually think the reverse is true, if people who don't "fully" grasp evolution don't try to defend it, lots of creationist bullshit would go completely uncountered. The only problem I can imagine is creationists wasting their time arguing against strawmen.
posted by delmoi at 8:55 PM on August 13, 2012


But what you can say is, if you were to go back in time to before this event was known to occur the probability of something like it happening would be lower without global warming. That's what I mean when I say "this probably wouldn't have happened"

This is sort of a weird statement. Due to the dynamical nature of weather, if you went back in time and changed the initial conditions (by "lower[ing] global warming") you would change how everything unfolds. So any specific event, like a hurricane, probably would not occur. You could do the same by *increasing* global temperature. A particular hurricane would probably not occur, but there may be two more at other times. So it makes little sense to talk about *specific* events being caused by global warming.

The way statisticians typically talk about causation is in the (approximate) number of events that would not have occurred had the conditions been different. Say, you change a population's diet, and cancer decreases from, say, 1% to .9%. When you work that out as a proportion of the population, you might say that (just for example) the diet change prevented 100,000 cancer cases. That doesn't mean that there were any particular cases that were prevented as a result of the diet change. It's just a statement about the estimated difference in the number of cases.

The same goes for weather. One cannot say that global warming causes any particular event.
posted by Philosopher Dirtbike at 1:11 AM on August 14, 2012


The horror in all of this is that UNTIL IT IMPACTS THE POWERFUL in a tangible and incontrovertible way, we will see nothing change. Those with wealth and influence will continue to enjoy both and will continue to fight those who say changes must be made until those very people become uncomfortable, see their bank accounts shrink or their children die or their mansions burn to the ground. And given the scale of that wealth, I suspect it will be a long, long time until that happens.
posted by kinnakeet at 8:30 AM on August 14, 2012


* sheepishly sticks head back in room *

Would it help stop the derail if I admitted that my initial comment was ill-stated because I was trying to make a dumb joke that was dumb?
posted by EmpressCallipygos at 9:34 AM on August 14, 2012




The same goes for weather. One cannot say that global warming causes any particular event.
Huh? You just said:
if you went back in time and changed the initial conditions (by "lower[ing] global warming") you would change how everything unfolds
Which means, of course that global warming was one of the 'causes'. That's how causality works. You can say that it's not a very useful conclusion, but it is still true.

Secondly, the important statement is "If global warming didn't exist, things like this event would have been less likely". That's a completely reasonable claim, assuming it's something that global warming makes more likely.

If you want to know how much 'blame' to assign global warming, you can just subtract the 'normal' probability Pn with the probability under global warming Pg and then divide by Pg

So if Pn = 1% and Pn = 5%, then 0.05-0.01 = 0.04 and 0.04/0.05 = 0.8.

So 80% of the 'blame' can be assigned to global warming.

That actually is a pretty useful number. If you were, for example, in the flood insurance business, you'd have to pay 5 times as much money each year if the the probability of a flood in any region were 5% instead of 1% (therefore, 80% of the cost is due to global warming)
posted by delmoi at 7:26 PM on August 15, 2012


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