Saturday, April 30, 2011

Global Warming and Tornadoes

Here is a post by Roy Spencer, climatologist and a Principal Research Scientist for the University of Alabama in Huntsville, as well as the U.S. Science Team Leader for the Advanced Microwave Scanning Radiometer (AMSR-E) on NASA’s Aqua satellite. He takes on the global warming crowd in this post on his blog:
I see the inevitable blame-humanity game has been reinvigorated by the recent tornado swarm. I have not read other meteorologists’ treatment of this issue, so what follows can be considered an independent opinion on the matter.

If there is one weather phenomenon global warming theory does NOT predict more of, it would be severe thunderstorms and tornadoes.

Tornadic thunderstorms do not require tropical-type warmth. In fact, tornadoes are almost unheard of in the tropics, despite frequent thunderstorm activity.

Instead, tornadoes require strong wind shear (wind speed and direction changing rapidly with height in the lower atmosphere), the kind which develops when cold and warm air masses “collide”. Of course, other elements must be present, such as an unstable airmass and sufficient low-level humidity, but wind shear is the key. Strong warm advection (warm air riding up and over the cooler air mass, which is also what causes the strong wind shear) in advance of a low pressure area riding along the boundary between the two air masses is where these storms form.

But contrasting air mass temperatures is the key. Active tornado seasons in the U.S. are almost always due to unusually COOL air persisting over the Midwest and Ohio Valley longer than it normally does as we transition into spring.

For example, the poster child for active tornado seasons was the Superoutbreak of 1974, which was during globally cool conditions. This year, we are seeing much cooler than normal conditions through the corn belt, even delaying the planting schedule. Cool La Nina years seem to favor more tornadoes, and we are now coming out of a persistent La Nina. The global-average temperature has plummeted by about 1 deg. F in just one year.

An unusually warm Gulf of Mexico of 1 or 2 degrees right now cannot explain the increase in contrast between warm and cold air masses which is key for tornado formation because that slight warmth cannot compete with the 10 to 20 degree below-normal air in the Midwest and Ohio Valley which has not wanted to give way to spring yet.

The “extra moisture” from the Gulf is not that important, because it’s almost always available this time of year…it’s the wind shear that caused this outbreak.

More tornadoes due to “global warming”, if such a thing happened, would be more tornadoes in Canada, where they don’t usually occur. NOT in Alabama.

It is well known that strong to violent tornado activity in the U.S. has decreased markedly since statistics began in the 1950s, which has also been a period of average warming. So, if anything, global warming causes FEWER tornado outbreaks…not more. In other words, more violent tornadoes would, if anything, be a sign of “global cooling”, not “global warming”.

Anyone who claims more tornadoes are caused by global warming is either misinformed, pandering, or delusional.
Despite the science, media reports are busy affirming that "global warming" has caused the increased number of tornadoes in the US southern states. This just proves that you shouldn't learn your "science" from the media. And you shouldn't "learn" anything from a public interest group since they are partisans with a viewpoint they are trying to sell. You need to be skeptical and look to facts.

Oh... and if you want to know whether "global warming" causes more hurricanes, take a look at Ryan Maue's research material:
Global Tropical Cyclone ACE does not show an upward trend in communion with global temperatures.

In the five years since 2006, Northern Hemisphere and overall global tropical cyclone (TC) accumulated cyclone energy (ACE) has decreased dramatically to the lowest levels in at least 30-years. Here we examine the strikingly large global interannual variability of TC ACE during the past 40-years and shed light on the large-scale climate mechanisms responsible for the recent historical downturn in TC activity. Much of the variability in global TC ACE is explained by the concomitant changes or evolution in the character of the El Nino Southern Oscillation (ENSO) and Pacific Decadal Oscillation (PDO). In the context of the Pacific climate variability and its effect on global TC activity, our results suggest that the ongoing period of heightened North Atlantic hurricane activity is related to decreases in storm activity elsewhere.
Instead of the simple relationship of "global temperatures rise and cause more hurricanes" the real relationship is very complex and dependent on large cycles in systems such as ENSO (El Niño/La Niña Southern Oscillation in the Pacific). But complex relationships don't "sell" simple messages like "CO2 causes global warming" or "global warming causes hurricanes" or "global warming causes sea level rise" of "human activity harms Mother Nature and she will strike back at us".

2 comments:

thomas said...

RY;

I am amazed at the human need to explain or blame something when things like this happen. There should be (probably is) someone claiming the end of the world is at hand.. Shouldn't Pat Robertson or his ilk be on the news blaming the sins of the people and saying that God is punishing them? Perhaps our deficit is to blame.. or we have strayed from our path of being a light to the world.. or, it is our war mongering.

All we should be focussed on is how to help those suffering from the bad weather and preparing for more to come or the possibility of worse events that will strain our non tax paying people even more.. We can't afford to sit by and not fund our government any longer. How will we pay for these catastrophes that occur with or without our understanding of why they happen?

RYviewpoint said...

Thomas: The right wing crazies are coming out of the woodwork telling people they "deserved" these tornadoes because they weren't "good enough" for a "loving" God. Here's one of the crazies, Calvin Beisner.

This Beisner character reminds me of the type of people who tell a rape victim that she "got what she deserved" because she "encouraged" her rapist by her dress, her conduct, her attitude, her words, her look, or just plain her sex.

When things go bad, like a natural disaster, you need support. In the dysfunctional parts of the world that means you family or your clan. In the more successful modern states that means a government that takes seriously its responsibilities for providing a social safety net. Sadly, a lot of Republicans want to shrink government down to the size where it can be "drowned in a bathtub". At that size, a disaster like the tornadoes in the deep South would be too overwhelming because there would be no resources.

I like the contrast between Obama and Bush. When Katrina hit, Bush stayed away, then finally flew over at 30,000 feet, and finally showed up to slap his good buddy Brown on the back and tell him he was doing a "heck of a job" while thousands had spent a week abandoned, without food or water, in the Superdome and the Convention Center. The US with its massive airlift capability that could put an aircraft carrier off the coast of Sumatra when the tsunami occurred in Christmas 2004 within a day and could put an aircraft carrier off the coast of Japan within a day of the tsunami there, wasn't able to get assistance, food, or water to thousands stranded in New Orleans, one of the major cities of the US.

Obama was on the spot in Alabama the day after the tornadoes offering federal assistance.

The difference is stark. Obama represents the Democratic party that believes that government has a role in helping people. Bush represented the Republican party that believes that "government is part of the problem, not the solution" and believed that the only real job was to reduce taxes on the rich again and again and again.

The contrast is stark. What is astounding is that something like 40% of the US population still hasn't "gotten it". They still swallow the swill dispensed by the Republicans. Tragic.