[americandream]

It would be amusing to discover who in their right mind would limit a definition of this dynamic natural phenomenon to planetary tilt. Can I have the link please.

science-dictionary.com reads as follows:

tropics

Definition

plural noun

(Earth Sciences) the region between the Tropic of Cancer and the Tropic of Capricorn, where the climate is hot and often humid

As for the "Jesus" bit, I should imagine you most certainly "can" unless you need assistance for whatever reason, but whether you "may" is another matter and beyond my remit as a mere mortal.

To suggest as you appear to, that planetary tilt alone circumscribe these "extremes",

Can I get another "Jesus"?

I'm not "suggesting" anything. I provided the scientific definition of "tropics".

[PrestonSturges]

In many cases, northern movement of climate zones doesn't really benefit in terms of permitting the growth of more tropical species, since killing frosts may just as severe as ever.

However, new plant diseases can show up as a result of minor climate changes. For fruit trees, canker, cedar rust, and fireblight are often the factor that really determines the range of specific varieties, and a change of 1/2 a climate zone can let disease wipe out established plants. Likewise, we'll see thrips killing more eastern hemlock.

[dohboi]

Yup, the over all effect of GW so far has been reduction in global plant growth.

link

[Expatriot]

It would be amusing to discover who in their right mind would limit a definition of this dynamic natural phenomenon . . . Definition

plural noun

(Earth Sciences) the region between the Tropic of Cancer and the Tropic of Capricorn, where the climate is hot and often humid

Wow. You quote something that explicitly repeats what I said was the definition. And you think it somehow doesn't.
Tropics defined only by tilt. Yes. Nothing dynamic about it, unless you are referring to the changing tilt of the earth over time.

[yeahbut]

Lookout: "Captain, there's an iceberg dead ahead sir!"

Captain: "Young man, there are many types of 'iceberg', as you insist on describing it. They range from growlers to ice islands. Now which is it?"

Lookout: "Does it really matter sir? We're going to run into it!"

Captain: "Of course it matters you young whippersnapper! Now get back out there and tell me if it's a dome, a pinnacle, or a wedge."

Lookout: "Er, I'm really not sure Captain, but don't you think we ought to slow down a bit sir?"

Captain: "Not until you admit it's not an iceberg."

Lookout: "Begging your pardon sir, but you're an idiot."

Captain: "Why you impudent devil! I'll have you keel-hauled, you wretched dog...ooh! Did anyone else feel that?"

[AgentR]

Where as, if the lookout had just said, "its a wedge, and a big one at that." The argument would conclude, and the ship would have turned in time.... As it was... Oops. to late.

[Newfie]

"Its a wedge!!!!!!!!!!!!!"


Are we turning?

Who is the Captain anyway?



Feels more like a 'weedgie'

[Subjectivist]

http://www.atmos.pku.edu.cn/yhu/Hadley-CMIP5.pdf

This research paper reports that the Hadley aka tropical cell has expanded 0.15 degrees lattitude over the last decade. That is about ten miles per decade or a mile per year. That might not sound like much however if you think about it that is actually two miles, one to the north of the equator and one to the south, and they are 24,000 square miles in each hemisphere. Each hemisphere gains an area of tropics the size of the us state of West Virginia each year or all together an area the size of Mississippi. That increase happens every year, year in and year out.

[dohboi]

Thanks for this, S.

The relatively gradual push north will eventually lead to a sudden shift in the basic structure of the system--at some point it will just take over the mid-latitude cell and so jump rather suddenly far north. Or perhaps we will waffle back and forth between a two- and a three-cell system?

It's a grand experiment, so I'm not sure anyone can reliably predict how it will play out. Expect the unexpected. But I doubt all the changes will be smoothly linear.

[Tanada]

Thanks for this, S.

The relatively gradual push north will eventually lead to a sudden shift in the basic structure of the system--at some point it will just take over the mid-latitude cell and so jump rather suddenly far north. Or perhaps we will waffle back and forth between a two- and a three-cell system?

It's a grand experiment, so I'm not sure anyone can reliably predict how it will play out. Expect the unexpected. But I doubt all the changes will be smoothly linear.

Smoothly Linear?!?

Nothing about the past tells me to expect a smoothly linear change, but hey if it lets you sleep at night more power too you.

[dohboi]

???

I said that I "doubt" the changes will be linear.

Time for some reading glasses, old man?

(I keep having to up the strength of mine--too much squinting at blog screens, I guess. )

[dohboi]

I was surprised to see in the recent report on abrupt climate change that expansion of the tropics in the southern hemisphere is even more certain than in the north.

[Subjectivist]

I was surprised to see in the recent report on abrupt climate change that expansion of the tropics in the southern hemisphere is even more certain than in the north.

Link? I would like to read that report.

[dohboi]

Here ya go:
http://www.nap.edu/catalog.php?record_id=18373

Long pdf file warning: ~200 pages!

[Subjectivist]

Here ya go:
http://www.nap.edu/catalog.php?record_id=18373

Long pdf file warning: ~200 pages!

Yikes! Thanx d, this is going to take a while lol.

[dohboi]

Yeah, there's lots of interesting stuff. I feel they 'protest too much' trying to downplay the threat of methane clathrates, and they don't bother citing anything from the two folks who have been working longest and most intimately in the relevant areas: Wadhams and Semiletov. The other thing I would have liked to see more discussion of is possibilities/probabilities of influence on the rest of the Northern Hemisphere (at least) from the ongoing collapse of Arctic sea ice volume, extent and area.

But one probably shouldn't expect cutting-edge dot-connecting from this kind of committee-written summary-of-established-research.

And this is the go-to place for that.

[Tanada]

I believe this thread and the information posted in it is relevant to both the Global Greening and Desertification debates.

As the tropic climate zones continue to expand poleward in both hemispheres the desert zone that borders them is being greened on the equatorial border of that zone. The key questions are,
1) Is the extension of the Desert Climate Zone on the temperate border of the zone expanding, staying static, or changing in some third fashion?
2) If the desert climate zone is also moving closer to the poles as the tropic zone expands is it moving faster, slower, or at the same rate as the Tropic zone is moving and a corollary, will it be over more or less land area than it was before it moved?

[dissident]

Thanks for this, S.

The relatively gradual push north will eventually lead to a sudden shift in the basic structure of the system--at some point it will just take over the mid-latitude cell and so jump rather suddenly far north. Or perhaps we will waffle back and forth between a two- and a three-cell system?

It's a grand experiment, so I'm not sure anyone can reliably predict how it will play out. Expect the unexpected. But I doubt all the changes will be smoothly linear.

Smoothly Linear?!?

Nothing about the past tells me to expect a smoothly linear change, but hey if it lets you sleep at night more power too you.

Believe it or not, but the tropical dynamical regime is vastly more stable than the middle latitude one. The tropics are basically quasi-linear in the zonally averaged view. This is why when they started reporting weather forecasts in Indonesia several years ago, they stopped them. Basically the same weather day in and day out. The only action is the wet and dry season cycle.

So the expansion of the Hadley circulation should have a high degree of monotonicity. It will be its coupling with extra-tropical dynamics that will introduce a good chunk of the variability and then there is ENSO.

[Ibon]

Believe it or not, but the tropical dynamical regime is vastly more stable than the middle latitude one. The tropics are basically quasi-linear in the zonally averaged view. This is why when they started reporting weather forecasts in Indonesia several years ago, they stopped them. Basically the same weather day in and day out. The only action is the wet and dry season cycle.

This is just one of the reasons why biodiversity is so much richer in the tropics than in temperate regions. They have been stable for hundreds of millions of years. The wet and dry cycles are annual but also geological. Pollen samples from ancient lake beds show that the Amazon basin was drier grassland habitat in the past. There are theories that the engine of biodiversity in the tropics happened through several geological cycles of wet and dry periods. During maximum dry periods tropical vegetation is restricted to riparian river flood plains and populations are separated by vast areas of grasslands. This separation if long enough splits species into separate populations so that when they are rejoined in wetter periods they no longer interbreed having become separate species.

Glaciers sweeping down through continents periodically on the other hand greatly reduces biodiversity. Less niches, less habitat.

[dissident]

Believe it or not, but the tropical dynamical regime is vastly more stable than the middle latitude one. The tropics are basically quasi-linear in the zonally averaged view. This is why when they started reporting weather forecasts in Indonesia several years ago, they stopped them. Basically the same weather day in and day out. The only action is the wet and dry season cycle.

This is just one of the reasons why biodiversity is so much richer in the tropics than in temperate regions. They have been stable for hundreds of millions of years. The wet and dry cycles are annual but also geological. Pollen samples from ancient lake beds show that the Amazon basin was drier grassland habitat in the past. There are theories that the engine of biodiversity in the tropics happened through several geological cycles of wet and dry periods. During maximum dry periods tropical vegetation is restricted to riparian river flood plains and populations are separated by vast areas of grasslands. This separation if long enough splits species into separate populations so that when they are rejoined in wetter periods they no longer interbreed having become separate species.

Glaciers sweeping down through continents periodically on the other hand greatly reduces biodiversity. Less niches, less habitat.

Indeed. The tropics are the main reservoir of plants and animals on this planet. The high latitudes are exposed to winter and long term obliteration by glaciers.

For now the tropics are relatively safe as the pumping of heat via the perpetual spawning of baroclinic eddies on the flanks of the Hadley circulation is effective. But eventually they will start to warm up at a faster rate and a lot of mammal life will be wiped out due to excessive wet bulb temperature.