Comments on: Yes, global warming can boost the most severe tornados

By: monika

monika — Fri, 15 Feb 2008 18:49:10 +0000

I think that global warming is connected to the nastier tornadoes and other weather issues.

By: Peter Foley

Peter Foley — Mon, 11 Feb 2008 04:02:50 +0000

Yet again the actual data doesn’t support the articles statement: If AGW is true, the atmosphere warms because of increased ‘green house’ warming there will be of course less delta T due to the lowered effects of solar radiation acting through the ‘blanket’. As one piles more blankets on the bed the the standard deviations of the interior (sheets) temps will decrease.(check out Mars and Venus for test cases) Tornadoes are the product of shears between masses of air. Deaths from Tornadoes don’t correlate to the alleged AGW. Higher numbers of REPORTED tornadoes are an artifact of radar and improved communications.
It appear Senator Kerry wishes to emulate the father of the Internet, Mr. Gore with unfounded assertations.
As one records a natural phenomenon more and more extremes will be recorded as time increses. In other words, DUH!
Question for the group: What have average wind speeds done during the alleged AGW period?
The final paragraph equals any phrase a gypsy fortune would utter to a junior high girl,” I see a tall dark handsome young man in your future…..”

By: Harold Brooks

Harold Brooks — Sun, 10 Feb 2008 03:30:51 +0000

Sorry, Dano, I thought you were referring to model work on the precip problem. I can’t recall the exact references off the top of my head, but there are several papers talking about the observed changes in precip distributions.

By: Paul K

Paul K — Sat, 09 Feb 2008 04:29:25 +0000

It’ the same old question. How many meteorological events does it take to screw up a climate? There was an Australian drought study last year that found different precipitation patterns on either side of the rabbit fence dividing cultivated and uncultivated land. This was possibly due, it was thought, to differences in reflective properties. The IPCC report cites land use and CO2 as the two causes of AGW. For some reason land use hasn’t gotten much attention in the discussion.

By: David B. Benson

David B. Benson — Fri, 08 Feb 2008 22:53:21 +0000

Beefeater — A trite and meaningless reply. How about thinking it through?

The industrial revolution began in, say, 1750. By 1880 already humans had burned enough fossil carbon to raise the concentration of carbon dioxide in the atmosphere by 20 ppm or so. This during an extended period when the natural forcings should lead to slightly less carbon dioxide in the atmosphere.

Now that I have spelled it out for you, does this suggest anything regarding your question?

By: Dano

Dano — Fri, 08 Feb 2008 22:02:48 +0000

I think one of the common chances for severe tornadic activity anyway, Harold, is out of MCCs with favorable jet positions (or frontal), so I agree that having shear at the scale described in the paper may be a bit much wrt tornadoes (altho hail is another story, back to your point, I’m close to being convinced).

I think you can get at the precip bit with PDI and many of the ag networks with pan evaporation that are out there now. I can’t go out and Google the papers right now, but IIRC there are a couple papers out there attempting to look at soil moisture and rainfall records to gauge the effects of what appears to be more episodic precip, esp in upper midwest (totals about the same, but more episodic hence more drought stress). I come at this from the plant side now, but I was a weatherman in the service ~25 years ago…long enuf to be dangerous, surely.

Best,

By: Harold Brooks

Harold Brooks — Fri, 08 Feb 2008 19:25:25 +0000

I think the aversion to CAPE has to do with the parameterization of convection in the model. Depending on the scheme, CAPE may be difficult to interpret as a proxy for convection. I agree that the paper is looking at an increase in PE (although I’m not sure I buy the increased generation of PE by the convection-it could be a synoptic association of regions of PE with high shear), but one of the critical points is that stronger storms, as defined by any direct or proxy estimate of updraft, don’t necessarily mean more or stronger tornadoes. Energetically, tornadoes aren’t very important in the context of the overall storm.

As far as precip is concerned, that’s a nasty problem on the scales of the models. The work on thunderstorms essentially is looking at relatively large scale environmental conditions, in a manner akin to a forecaster looking for the large area of potential threat for storms, not as a forecaster warning on a particular storm. Converting those large-scale conditions to precip is really challenging.

By: Paul K

Paul K — Fri, 08 Feb 2008 19:22:05 +0000

Harold Brooks,
Thanks for explaining the contents of the GRL paper much better than I could have. Joe cited the paper to mockingly refute Roger Edwards’ statement that “no scientific studies solidly relate climatic global temperature trends to tornadoes.” Clearly, it does not.

By: Dano

Dano — Fri, 08 Feb 2008 18:36:02 +0000

I agree Harold, and it is a rather confusing paper, but they are saying that increased updraft speed increases shear [15] due to the increased generation of potential energy.

This is perhaps made more confusing than it should be because they don’t like CAPE (maybe they had a word limit or suggestion to take it out). Wrt your intensity statement, if I think of PE of the storms rather than whether simply hail or tornadic activity occurs as a result, it becomes clearer for me to understand what they are trying to say.

I’d also like to see a bit more work on convective activity wrt more intense precip episodes, as this has a lot of effect on soil moisture flux & crop health and also lessened evapotranspiration, which is less moisture for cloud formation overall.

Best,

By: Harold Brooks

Harold Brooks — Fri, 08 Feb 2008 16:13:07 +0000

I no longer have a sub so I can only read the abstract, but I think it does. Certainly I have had issues in the past with Joe’s interpretations, but not this time. Essentially, the paper claims frequency of storms may decrease, but the frequency of the most intense will increase.

But tornadic storms are not necessarily more intense than non-tornadic storms. The measure of intensity they use in the paper is parameterized updraft strength and updraft strength is tied much more closely to hail than to tornadoes. The decrease in environmental wind shear the paper reports is detrimental for tornadoes.

The press release and the paper seem somewhat disconnected. The only mention of tornadoes in the text is in a background sentence, “The central/east U.S. experiences the most severe thunderstorms and tornadoes on Earth.” The paper makes no attempt to link changes in tornado frequency and intensity to the modelled environmental changes. When I read it, without seeing the press release, I assumed the results applied to the hail problem, mostly, and that the results were consistent with a couple of other papers that were published last year.

There’s also some in-press historical work on hail and environmental changes in the last quarter of the 20th century that suggests a relationship between US mean temperatures and large hail occurrence, but the record isn’t long enough to reach statistical significance, given the problems in the reporting database.