Colours(Canadian spelling thereof) around the Ottawa area are fantastic this year. A lot of reds and golds. Reply: I am not surprised. A decent amount of rain this summer then some warm days and cool nights early in the fall.

It's freakish. Some of the old sugar maples are vibrant though others have simply shed their dull leaves. The norway maples are still green like mid-summer. Over the last several Falls, the contrast has only increased. Human co2 is definitely having an effect.

"The United States Department of Agriculture (USDA) has just started funding a study"

Great! What else can we waste more taxpayer money on?

"Something is clearly happening to make the colours less vivid"

Ya, nature is happening. No wait, must be mans fault because we all know how much trees hate CO2, right? I've been a native New Englander all my life. When we get alot of moisture, it seems to make the colors less vibrant and more rusty in appearance.

Also consider that in 2008, NH had it's greatest maple syrup production compared to the last 5 years. We also set record snow fall as well last December. Global warming? Not so much in NH. Atleast nothing to be alarmed about.

A thousand apologies for referencing my backyard weather report.

Colors, outside the Montreal area, in particular the Eastern Townships are simply stunning!

Many bright reds ......more than I can remember in previous years.

While I guess it's possible that the temperature difference between day and night is becoming less, I've also noticed that daytime highs are also reduced.

Lack of daytime warming also contributes to reducing the variances between the two and would therefore indicate global cooling.

I guess it depends on your agenda ...........

Faded this autumn and the previous one. Locally I blaim warmer nights.

I dont live up north to confirm that but if it is happeneing it would probaly be because winter might come in a more sudden or dramatic way instead of a gradual transfer into winter that causes those colorful leafs.Do you think my theory is plausible?

Brilliant as always here in Binghamton,NY.There has been no loss of brilliance here over the last 5,10,20 or 30 years.

This is ridiculous. In my lifetime I've seen great years here in CT and fair years. Warmer years the foliage changes a little later. That's all. Moisture seems to play a role however.
We've had plenty of cool nights and warm days this fall. Just the other day we were around 62F for a high and low 30s and frost at night. The colors look great and maybe a bit early.

Kind of funny, I was walking through my garden yesterday (taking a break from my home business), checking out my specimen Japanese maples, the plants, and the trees and I was thinking, wow, it is going to be a beautiful fall this year. We have large patches of color and the colors are pretty vibrant. I live on almost 2 acres with all old trees in a semi-rural area in the Northeast. I went on a trail ride on my horse in the woods this afternoon and the colors were just beginning but they were looking good. I didn't get the feeling that it was going to be a dud this year. I remember back a couple of years when it was pretty warm and dry (global warming) and we were in a semi-drought and for those years, the fall colors were not so good. Also because it was so dry, a lot of the leaves turned brown and fell off.

When I lived in San Diego, for those deciduous trees that were on irrigation, we had some pretty spectacular fall colors. But that was then, now it is dry and hot and perpetually brown, since they have water shortages now. I was back in San Diego a few weeks ago and visited a friend who has a large liquid amber tree, which is on a drip system. She says it turns vibrant red in the fall which it had started doing when I was there. She was proud of that tree, she was. Anyway, it seems like water/rain is a large player also in addition to global warming. Shortage of global water is going to be the next issue if not already.

Oh what a crock (yet another) from these lunatics! Better cut the CO2 and throw a wrench into the world economies (which they don't need) by taxing everthing in site so we can control the climate and prevent the pretty leaves from not changing colors! These people make me sick!

I wish there was glo-BULL warming so the leaves would not change colors! Leaves changing colors is grossly over-rated and only singifies another crappy winter is on the horizon. Any of you "pretty leaf"/cold weather loving tree huggers out there are more than welcome come and RAKE all the of "PRETTY LEAVES" that I have to trudge through yet agin. Oh, Oh, that's different, I am sorry that's right. Just like it's different when you belong to a certain political party. I know how it is! Screw the leaves. I want warmth, which is NOT HAPPENING!

DENY DENY DENY THE GLO-BULL WARMING LIE!!!!!

And here's another crock from the "Union of Concerned Scientists," with their suck-ups in the local one-sided biased media:

http://www.post-gazette.com/pg/08276/916784-113.stm

Scorch PA? When??? When??? I miss summer the way it used to be!! When??? And as for the farce that is the Union of Concerned Scientists, they are just that. A FARCE AND FRAUD. Their president isn't even a scientist. He is a public policy lobbiest, and hack with a masters degree in political studies! Fraud. Propaganda. Fiction. Call it what you want. It's all further evidence that glo-BULL Warming is the biggest scam in the history of mankind.

Temperatures are running normal to well below normal for nearly the entire country in 2008, but unfortunately the trees read realclimate every day and believe that it is actually anomalously warm.

This causes them to behave badly.

http://www.hprcc.unl.edu/products/maps/acis/YearTDeptUS.png

I don't know about changes in colors compared to years past, but I noticed that here in Fairfield County, Conn. the change of color is coming later than before. As we go into Columbuis Day weekend, most of the trees here are still green with a small amout of color. Back in late 70's, there was usually more than 50% color here by Columbus Day. Also, the time of peak leaf fall seems to be later. In the late 70's,it occurred around the 3rd week of Oct, by the 20th or 21st, with the trees 80% bare by Nov 1. In the past few years, many trees have still been nearly full of leaves on Halloween, with the trees not bare until well after Veterans Day. (Nov 11).

"The United States Department of Agriculture (USDA) has just started funding a study into claims that the northern states fall colors are also fading away with climate change."

What is wrong with this governmant? They are really going to spend my money to see if leaves are green or not?

Since I live in the Mid South, I'll have to get back to you in 3 or 4 weeks on how our fall foliage looks this year. We're still pretty green here at the moment.

Wow!
One more thing to add to our list of things we blame on AGW.

My personal experience demonstrates with an IPCC-like high degree of certainty that climate warming over the past 25 years has resulted in an almost complete loss of fall color brilliance. I have fond memories of brilliant fall foliage in the gorges around Ithaca, NY and Cornell University in the mid 1980's. These colors have all but disappeared since 2002.

I should mention that I moved to Tampa, FL in 2002, but this has little impact on the conclusion, since Mannian teleconnections of foliage behavior in Florida imply similar changes in Ithaca, NY.

;-)

I don't think I will agree with that assessment. The traditional yellows and reds have more to do with species. Maples turn red and are more indicative of a forest that has more tolerant species.

Over the past few decades, oak has been king, and many forest landowners have managed for oak regeneration. Oak doesn't have the vibrant colors that the maples have.

Maple has been deemed a "weed" tree by the industry in the recent past and have been taken out of the forests. Reply: I assume you mean red and silver maples. The sugar maple is not a weed tree.

So, I think you have to put something in there about forest composition before you start blaming the whole thing on climate change.

For nearly 35 years we have been making the trek up to North Carolina, Asheville, Cherokee, Bear Paw, the second week of October (we live in Atlanta), just before the 'leafies' jam the highways, to get that fall 'fix' of the mountains. Naturally we have to get yet another lament from the 'scientists' of AGW that boohoohoo, we are losing the sharp fall colors. A check in the northeast shows little of no change on the colors. As usual these Hysterics have no grasp to the fact that all their postulations are made upon conjecture as to the course of natural climate variations. And the fact that even if we are losing some of the brilliant colors that is not another reason to run out and propose some addendum's to the Kyoto protocol.

From visitnc.com North Carolina Fall Color Report: Good news on the fall leaf color front - we�ve had another week of great weather and the color change in the mountains has really picked up steam. There�s still about a week or so to go before color�s peak in Ashe and Watauga counties, but some areas are near their peak in Avery County, especially around Grandfather Mountain. In Ashe and Watauga counties you can now see the mountains beginning to take on color below 4,000�. If the weather conditions hold up, we should have peak color in 7-10 days, whereas it may be near peak levels this weekend in the Grandfather area. It is supposed to be a bit rainy and cool this week (Wednesday through Saturday), but I don�t think the duration of this weather system will dampen the intensity of the fall colors, since the previous two weeks have been nearly perfect weather-wise.

Jesse Pope, chief naturalist from Grandfather Mountain writes: �We are starting to see pretty good color widespread above 5,000 feet. More and more color is showing up all the way down to 3,500�. The Heath Bald areas are in full color on the flanks of Grandfather just above the Blue Ridge Parkway, and around 4500�.

Many species are starting to show off good fall color and include: Mountain Ash (brilliant red), American Ash (burgundy and yellow), many huckleberries and other Vaccinium species (bright red to burgundy), Sugar Maples, Red Maples, Yellow Buckeye, Yellow Birch, Hop Hornbeam (yellow), Pignut Hickory (yellow/brown), Red Oak (red,yellow, and brown), Chestnut Oak (yellow/rust), hobblebush (red), and Sourwood (red), just to name a few.�

Here in Ashe and Watauga counties, the birches and maples are really beginning to show off their colors, and oaks, dogwoods, hickories and cherries are adding to that. The tulip poplars, always late with their color, are finally beginning to turn, and will eventually result in bright yellow splotches on the hillsides when they reach their peak in another week or two. Some of you may notice lots of brown leaves on the black locusts. This is due to the locust leaf miner, a native insect that defoliates these trees late each summer. The trees seem to withstand these insects without too much adverse effects.

Autumn is getting into full swing here in Scotland, personallu I havent noticed a difference in colour. I think such observations risk being incredibly subjective.

When you have a dry late summer the leaves always tend to have less color and drop quickly in the fall. Since you don't describe what is a normal fall season it is difficult to compare. But, I have seen brightly color leaves one year followed by not so bright the next year. Nothing stays exactly the same forever and changes are part of the evolution cycle.

Fantastic color in New Hampshire this year. Much more red than usual, the leaves turned early this year, which is no doubt a sign of global warming.

Fall colors in bershires and catskills are fabulous this year, All the way down to NYC great fall colors happening. Last year was also a wonderfull fall foliage display!

Here in central NY the maples are at peak with plenty of brilliant orange and reds. The mountain side along I88 is just beautiful today. Ash leaves are on the downside and the Oaks are still green and will be for a few weeks. I'd say it is just about normal but then my time frame for observation here is only 35 years.
It seems the amount of rain we get during the August and early September determines just how the colors are. Of course a heavy rain and wind storm in early October can wipe the leaves off the trees in a day.
But this is all just anecdotal observations and like the man says beauty is in the eyes of the beholder. (Especially if you can get grant money for looking at fall foliage!!!! Don’t you just love how everybody is getting on the gravy train!)
LOL Everybody please have a great weekend and enjoy the fall colors.

im from the uk and i'd say that the autumn colours do seem to be fading. the trees also don't seem to change all at once, only a few patches at a time. i've also noticed that autumn seems to be coming about a month later than it used to. by now, years ago many of the trees would have changed colour but only a few have so far this year.

I spent yesterday producing serious amounts of Co2 peddling myself from NYC to Newburgh,NY. and I only have this to say: B.......BALONEY.

Nice picture.

Nothing new here, move along

http://www.ecoenquirer.com/NASA-vegetation.htm

This autumn heat is affecting me too. 41 degrees now with snow and rain forecast all weekend.

Reply: You should take a drive down to Colorado Springs. 73 degrees now. Thunderstorms tomorrow.

Very subjective. I "think" colors are better/worse than last year. I "remember" bright colors when I was younger. Not even a scientific study had been done, yet it's being blamed on AGW.

Hogwash.

This is ridiculous. Color is beautiful in Ohio as usual. In the last 40 years, there have always been good and bad years. Most of the time good years. This global warming stuff is getting out of hand!

I live in southern Maine and the colors look pretty much the same as they always do, if anything they seem to have turned early and I would even venture to say we are at peak right now. I feel global warming is a crock, the earth might be warming but humans only have a minimal impact on it. We have been on the earth way to short of a time period to try and guess what is going to happen. The earth is and will always self correct any issues it has. I haven't seen any evidence of global warming here. It has been in the lower 30's at night with highs in the 50's here. It is a little too soon for that like that.

This fall will produce breathtaking images which I intend to capture with my camera. I don't know what the author is talking about but then he doesn't either. Maybe he stuck his head outside on a cloudy day and concluded that the leaves weren't as vibrant as he remembers. Just more nonsense from overzealous AGW hustlers.

The Ohio Department of Natural Resources provides extensive coverage of fall color and has declared, "It has been very nice weather for fall color. The recent onset of cool nights will help bring out the vibrancy of color," said Casey Munchel, fall color specialist for the ODNR Division of Forestry." She goes on to report that the color will be "more vibrant than last year."

Here is a link to this very excellent web site:
http://www.dnr.state.oh.us/tabid/9584/default.aspx

Brett: Since you are in PA I recommend a trip into the Allegheny National Forest - visit the Kinzua Dam area and take your camera. If you like fall color then you won't be disappointed.

Reply: I am sure it is beautiful.

From The Desk of The Weekly Standard,

I think you could literally destroy life with your words.I truly believe this after reading your post.
I have a degree in forest biology,horticulture and a great passion for our atmosphere and how it works.It really angers me to share a world with people like your self.How could you hate the cold so much.Cold is as right as warmth,rain,wind etc.

I have noticed over the past 10 years here in south central Maine that the colors have tended to be muted no matter what the conditions--dry summers, wet summers and early fall. I have also noticed that our frosts seem to be coming on 2 to 3 weeks later than back in the 60's and 70's. Finally, I have a 40 year old Norway Maple on my front lawn. It has never had much color, with the leaves tending to merely dry up and fall. Again, over the last 10 years, the timing of this tree's leaf drop appears to be 10-days to 2 weeks later than it was when we first moved into our house in 1977. It is now not unusual for me to be raking these leaves into the first week of November instead of during the 2nd half of October.

Brett,

Or I could drive up to Wyoming for 36" of snow this weekend!
http://www.accuweather.com/news-story.asp?partner=forecastfox&traveler=0&zipChg=1&article=1

Reply: No doubt!

I've definitely noticed the fall colors being delayed over the past few years. Last year was extreme. I went hiking in late October, because that is typically the peak color around these parts. But to my surprise there was very little color. Everything was green. And I'm talking about 2,000 feet in elevation. October 2007 was the warmest October on record around here, so I'm sure that has something to do with it, along with the extreme drought experienced in August.

I've also noticed an increase in the number of extreme precipitation over the past decade or so. It seems we'll go weeks without much rain, and then we'll get hit by 5+" of rain in a day. The annual rainfall, therefore, has increased, but the frequency of precipitation events is more sparse.

You're right, Rich, everything is a waste of taxpayer money, unless it involves buying some new tanks or fighter jets. Or bailing out Gordon Gecko on Wall Street. So many holes have been blown through the laissez-faire doctrine that it's now looking like swiss cheese. And yet, you continue to spout your nonsense.

The reason we have not the long autumn is that it gets very cold very early, so the leaves falls directly.

Is that caused by global WARMING?

Yes, everything is global warming (which needs political action). Sorry I'm asked!

Was'nt there a paper in Nature earlier this year that said that trees regulate the temperature of their leaves at about 70F no matter what was happening to the climate?

The trees thus adapt and don't go in for colour monitoring much. Perhaps we should follow their example.

Denis,
And old timers during the 1950s and 1960s would gripe at how cold autumns and winters were comapred to the 1910s and 1920s of thier childhoods. My great grand parents on my mother's side escaped Iowa for Indiana during the 1930s in order to escape the hot drought conditions of the Plains. Thier farm in Northern Indiana would fail during the late 30s early 40s due to excessive spring frosts.

During this time of so-called AGW, fruit farms in Southern Michigan have suffered 3 out of 4 years due to May frosts. This autumn in East Asia, Russian farmers have had a delay in harvesting thier summer wheat due to September frosts. And now with the global credit freeze, they may not have enough money to bring thier wheat to market.

I think you could literally destroy life with your words.I truly believe this after reading your post.
I have a degree in forest biology,horticulture and a great passion for our atmosphere and how it works.It really angers me to share a world with people like your self.How could you hate the cold so much.Cold is as right as warmth,rain,wind etc.

REPLY: Really? Does it anger you? Well Marco, let me tell you what angers me. It angers me to share a world with people who constantly preach a LIE to promote/force their (leftist) political agenda on the populace of a capitalist repbublic that was doing just fine until touchee feelee politics disgisued as (junk) science entered the fray. All of this with the help of the media, that is supposed to be objective and tell both sides of a story.

Also, yes, I HATE COLD. It's number 1 on my hit parade of things I detest most in this world. And yes, I would welcome a permanent end to cold in any way shape or form in any location on this planet. There is NOTHING postitive about cold. NOTHING. I challege you to prove other wise to this to this blog.

Now then, If you would like for me to run down every nook and crany as to why I hate the cold so much, I will. But something tells me that this blog has heard it before.

Any more questions?

I'd rather sweat and swelter, than shovel, shiver, slip, slide, scrape, salt and slop. I NEED GLO-BULL WARMING! 24/7/365 (& 366 on leap year)!

Oh, one other thing, Marco. How can you sit there and accuse me of the premis that I could literally destroy life with my words and say that cold is as right as warmth,rain,wind etc., when cold probably does more harm than good on this planet? Your guilt trip is not going to work. And, I am curious, Just where in the world are you? Lapland? Siberia? The Himalayas? Jan Mayan Island? Antartica? Or are you in the Caymans or Miami sipping a Dacquari or two? Give me a break.

DENY DENY DENY THE GLO-BULL WARMING LIE!!!!!

I have commented how the past few years (3-4) seemed dull, but this year the colors are vibrant and fantastic.

Three questions.

1. How could the perceived intensity of foliage color (New Jersey spelling)be measured, and the intensity of past seasons be reconstructed?

2. Assuming that this methodological problem could be solved, and a decrease in intensity established, would temperature changes be the only possible cause? Couldn't such a change be a direct response to enhanced atmospheric CO2?

3. Deciduous plants evolved millions of years ago. Haven't they adapted to swings in climate much greater even than Dr Hansen's wildest dreams?
In other words, so what?

Last October was the warmest on record here in New Jersey, and leaf fall was accordingly late and unspectacular. Joe Bastardi had prepared his readers for this La Nina-induced 'unending summer'. So one might say the immediate trigger of an exceptionally warm fall in the Northeast was actually a cooling event in the tropical mid-Pacific!

I also noticed, and my back noticed as well, that the volume of foliage and the richness of the late green color of the leaves seemed enhanced. Since color change, for all its aesthetic appeal, is a symptom of plants under stress, one might argue that this phenomenon of later and less intense color change is an improvement in the well-being of the green world.

From the Desk of the Weekly Standard,

I tried to answer your questions but for some reason I had less space than usual.I couldn't scroll the page down.Maybe Brett is giving us less space so we keep the posts short.
Oh and one more thing.I live just north of Toronto.

Reply: No, I am not limiting the space. Must be some glitch.

P.Curly:I live in Fairfield county as well and you are dead on about the colors. It's just green, and have you noticed one snow fall in two years. Seems to be getting warmer all the time!
Think if you lived in Alaska or a south sea Island. Man you would know the difference. Just because we are lucky to live here, doesn't stop the world from going round. Americans are basically spoiled, but this will change in time. KIPP

In southern New Hampshire the colors are beautiful. Swamp Maples are past peak, after a truly gorgeous display, but Sugar Maples are still gaining color along the Main Streets.

Dry summers make for duller colors, in my experience. We had plenty of rain this summer.

Message to Thor: Norway Maples, not a native species, often never change in New Hampshire, and the leaves often fall from the trees green.

Reply: But, they make a great shade tree. Not so friendly to the grass underneath though.

I mentioned this last spring: Sugar Maples are not native to the coastal plain, south and east of the Berkshires and Manadnocks. Native Americans had no word for sugar on the coastal plain, and actually sneered at people who ate it, while Native Americans to the north and up in the hills had a word for sugar, and in some cases processed amazing amounts of it.

It was the Europeans, arriving in the Little Ice Age, who successfully transplanted the Sugar Maple out onto the coastal plain, and made good money at it. However it would not at all surprise me if those Maples were now stressed because, in case you haven't noticed, the Little Ice Age is over.

Maples began changing around here in mid-August, which freaked people out a bit. I think it was largely due to a long spell of dark weather, which fooled the trees into thinking days were shorter. Once the rainy spell gave way to a long dry spell, the Maples stopped changing. However they now are far ahead of last year, when we had an amazingly warm October, including a day that touched ninety degrees. This year is cooler, and I'd say the Maples are changing ahead of "normal," (whatever that is.)

However, to return to the point of this thread, the foliage is most definitely not "less brilliant" this far north.

Oiznop, I love your rants, don't stop! My wife and I raked all day in the yard and the leaves are only about half fallen off the trees. Colours are pretty good this year though.
Cold kills many times more people every year than heat, that is indisputable.

We live in Western Wisconsin..........the colors are beautiful this year. More brilliant than the last couple years. Even the white oaks in the woods are a deep red or maroon color. I have been out working in a mixed hardwood forest this last week and would like to show these 'scientist' the colors.

Don't they understand that everything in nature has an ebb and flow to it? The tides, the moon phases, hours of daylight,,,,,,,,,so why wouldn't the temperature too. Also, I was taught that the color change had more to do with the length of daylight than temp. Different scientists I guess : )

"You're right, Rich, everything is a waste of taxpayer money, unless it involves buying some new tanks or fighter jets."

No Mark, not everything is a waste of money, but much is. Certainly updating our armed forces with the most technologically advanced systems is imperative to the security of this country.

"So many holes have been blown through the laissez-faire doctrine that it's now looking like swiss cheese."

Anyway, back to the topic at hand... we just came back from Lake Winnipesaukee and riding around on our evil carbon emitting boat. The fall colors are coming in real nice now. Soon enough I'll be up there on my sled doing 100+ mph on top of the ICE. Sound the alarm!!!!

Here in far western Md ,the colors where I am at are at peak to just past and have been as bright and colorful as ever.

Reply: The colors here in central PA are a few days from peak but are better than average this year and I think the September rains saved the day after that very dry August.

The observations about the late and uneven coler change are correct. This has been the norm the last decade and a half. Warmer conditions, more co2 of which man is contributing has to be the reason. The observations about low frequency of rainfall yet more intense rains are also correct.

Marco: Instead of looking for an answer to late fall conditions, and the apparent lack of brightness of colours in Italy, we here much testimony, about everything being fine "in my back yard". In America we need a world perspective to adequately discuss AGW. Or at least a disscusion about causation. Does an abundance of CO2, or a difference between cold nights and hot days have an effect on colour. Cold weather, is a part of life as much as warm weather is. If the fish didn't have La Nina's we would have less of them. They stimulate the growth of plankton.
Don,t you find it an insult to be asked where you come from? If you are not from America, Welcome!
KIPP

Kipp,

I live in central CT. The colors here are outstanding and very close to peak. Peak here is usually the middle of October, but I've seen it later in the month on warm years.(1996 was very late for example. Leaves on trees well into November) This year we're slightly early if anything. As for your green colors in Fairfield County, I'm not sure you realize there's a big difference in the state between the coastline and the north. Foliage in your area of the state will peak later in the month due to the fact it's milder because of the ocean influence. Hence while I'm earler than you, I'm later than the Northwest Hills, which my guess are at peak. Kipp, if you want to see some great color take a ride up route 7 north. (you must be close to 7) It's a great ride up through Cornwall, Canaan, etc. My suggestion would be to go all the way into the Berkshires in MA. I think think you'll agree the fall colors look great.
By the way the colors in my town are as good as I ever seen.

Also, in terms of snowfall, again Kipp you're going to get much less snow than I will and the northern part of the state will. I believe Bridgeport averages around 27" of snow per year, while where I am we average around 50". By the way Norfolk I believe averages around 100". Like I said the ocean has a big influence.

If you want more snow and earlier fall colors move north.

Mark:

Just out of curiousity, when you rake those leaves and put them in your four wheeled transporting device for disposal, are the leaves in the front or back seat? In the trunk of a?, or on the outside of the vehicle behind you?

Kipp,
Studies show that an increase in CO2 levels lengthens the period of photosynthesis, thus delaying or inhibiting color change.More importantly pollution levels(Nitrogen Dioxide, Sulphur dioxide)have increased over the last century to levels that cause stress and damage to trees.The ideal conditions for vibrant fall foliage are warm sunny days and cool crisp nights just above freezing.During this time veins leading into the leaves gradually close preventing the sugars from moving out.This summer in Southern Ontario, for example air masses have been perdominatly from the North, thus having lower levels of pollution and frequent rainfall in conjuction with ideal fall temperatures making this years fall foliage the best I've ever seen.

Kipp:

This study doesn't even rate being called a theory, it's a hypothesis. The only reason this story even gets publicity is because they are blaming AGW. I love it, local conditions prove AGW, except temperatures, that can only be done globally.

"it's cool here today"-man, you have to think globally.

"the leaf color may be faded here today"-man, the local conditions are caused by global warming!

Try to stay consistant.

Here is an informative link explaining the chemistry of fall color change.

http://scifun.chem.wisc.edu/CHEMWEEK/fallcolr/fallcolr.html

In brief, yellow or golden color is produced by carotenes. These pigments are present in leaves throughout the growing season, but are overwhelmed by the green of chlorophyl. With lowering temps and declining hours and angles of light, chlorophyl breaks down and the pre-exising carotenes appear.

Red color, on the other hand, is produced by anthocyanin, which is synthesized in the fall from sugars and is thus dependent on the quantity of sugars the leaf has synthesized through the summer. This quantity, in turn, is dependent on weather factors, especially on rainfall. Rainfall totals in early fall that are moderately below normal seem to be associated with maximum production of anthocyanin. If that is the case, since rainfall totals in the Northeast were way above normal for September due to tropical events, we should not expect optimum colors this fall.

It's great colors in 2008 for UK autumn foliage

http://news.bbc.co.uk/1/hi/uk/7679465.stm

Remarkably, "unusual weather" is the culprit, just as it would be were the colors appearing to be fading