Tree rings may underestimate climate response to volcanic eruptions: study

Feb 05, 2012

Some climate cooling caused by past volcanic eruptions may not be evident in tree-ring reconstructions of temperature change because large enough temperature drops lead to greatly shortened or even absent growing seasons, according to climate researchers, who compared tree-ring temperature reconstructions with model simulations of past temperature changes.

"We know these tree rings capture most temperature changes quite well," said Michael Mann, professor of meteorology and and director of the Penn State Center. "But the problem appears to be in their response to the intense short-term cooling that occurs following a very large . Explosive volcanic eruptions place particulates called aerosols into the stratosphere, reflecting back some fraction of incoming sunlight and cooling the planet for several years following the eruption."

are used as proxies for climate because trees create unique rings each year that often reflect the that influenced the growing season that year. For reconstructing , tree-ring researchers seek trees growing at the extremes of their growth range. Inferring temperature changes required going to locations either at the tree line caused by elevation or at the boreal tree line, the northern most place where the trees will grow.

For these trees, growth is almost entirely controlled by temperature, rather than precipitation, or sunlight, yielding a good proxy record of surface temperature changes.

"The problem is that these trees are so close to the threshold for growth, that if the temperature drops just a couple of degrees, there is little or no growth and a loss of sensitivity to any further cooling. In extreme cases, there may be no growth ring at all," said Mann. "If no ring was formed in a given year, that creates a further complication, introducing an error in the chronology established by counting rings back in time."

The researchers compared temperature reconstructions from actual tree-ring data with temperature estimates from climate models driven with past volcanic eruptions.

Comparing the model-simulated temperatures to the Northern Hemisphere temperatures reconstructed from tree-ring thickness, Mann, working with Jose D. Fuentes, professor of meteorology, Penn State, and Scott Rutherford, associate professor of environmental science, Roger Williams University, found the overall level of agreement to be quite good.

However, they report in the current issue of Nature Geoscience that "there is one glaring inconsistency; the response to the three largest tropical eruptions -- AD 1258/1259, 1452/1453 and the 1809+1815 double pulse of eruptions -- is sharply reduced in the reconstruction."

Following the 1258 eruption, the climate predict a drop of 3.5 degrees Fahrenheit, but the tree ring-based reconstruction shows only about a 1 degree Fahrenheit dip and the dip occurs several years too late. The other large eruptions showed the same type of discrepancy.

Using a theoretical model of tree-growth driven by the simulated , the team determined that the cooling response recorded by the trees after a volcanic eruption was limited by biological growth effects. Any temperature drop exceeding roughly 1 degree Fahrenheit would lead to minimal tree growth and an inability of trees to record any further cooling. When growth is minimal enough, it is likely that a ring will not be detectable for that year.

The potential absence of rings in the first one to three years following eruption further degrades the temperature reconstruction. Because tree-ring information is averaged across many locations to obtain a representative estimate of northern hemisphere temperature, tree-ring records with and without missing rings for a given year are merged, leading to a smearing and reduced and delayed apparent cooling.

The researchers also noted that aerosol particles forced into the air by volcanoes block some direct sunlight causing cooling and they produce more indirect, scattered light at the surface. Trees like indirect sunlight and grow better under those conditions. However, this effect is small compared to that of lower temperatures and shorter .

By accounting for these various effects in the tree growth model, the researchers were able to reproduce the reduced and smeared cooling seen in the actual tree-ring reconstruction, including the near absence -- and delay -- of cooling following the massive 1258 eruption.

"Scientists look at the past response of the climate to natural factors like volcanoes to better understand how sensitive Earth's climate might be to the human impact of increasing greenhouse gas concentrations," said Mann. "Our findings suggest that past studies using tree-ring data to infer this sensitivity have likely underestimated it."

Explore further: NASA eyes powerful bands of thunderstorms in newborn Tropical Storm Iselle

Related Stories

Volcanoes cool the tropics, say researchers

Jan 05, 2009

Climate researchers have shown that big volcanic eruptions over the past 450 years have temporarily cooled weather in the tropics—but suggest that such effects may have been masked in the 20th century by ...

Tree rings open door on 1100 years of El Nino

May 27, 2011

(PhysOrg.com) -- El Nino and La Nina, the periodic shifts in Pacific Ocean temperatures, affect weather around the globe, and many scientists have speculated that a warming planet will make those fluctuations ...

Tree rings tell a 1,100-year history of El Nino

May 06, 2011

El Niño and its partner La Niña, the warm and cold phases in the eastern half of the tropical Pacific, play havoc with climate worldwide. Predicting El Niño events more than several months ahead ...

Recommended for you

Cordilleran terrane collage

6 hours ago

In the August 2014 issue of Lithosphere, Steve Israel of the Yukon Geological Survey and colleagues provide conclusions regarding the North American Cordillera that they say "are provocative in that they b ...

NASA sees Tropical Storm Halong's 'best side'

8 hours ago

NASA satellite data showed Tropical Storm Halong's "best side" or most powerful side was east of its center. That's where the coldest cloud top temperatures and strongest thunderstorms appeared on satellite ...

User comments : 22

Adjust slider to filter visible comments by rank

Display comments: newest first

Going
not rated yet Feb 05, 2012
Could varved clays, seasonal bands in lake bed deposits, not be used to explore the years where volcanic particles are present in the atmosphere and the amount of biological activity in those years.
julianpenrod
1.6 / 5 (7) Feb 05, 2012
When you're working to promote a lie, it can be helpful to have support among "collegaues". The "researchers" pushing that the Little Ice Age began four centuries before it did were stymied by the existence of disagreeing information. Such as that tree tings did not show such temperature drops. So they cobbled together the fiction that tree rings do not accurately reflect temperature. Then the present that as a "separate" "discovery" and use it to maintain the claim for the early beginning of the Little Ice Age.
julianpenrod
1 / 5 (4) Feb 05, 2012
Extremely ironic, though. This will likely by defended by the anti-climate change forces who play with words to say the unnatural heating of the air is actually, "the earth warming up after the cooling". BUt, another favorite point for the "skeptics" is the supposed "deception" by climate scientists. But the root of that incident was the realization that tree rings are not necessarily so reliable in revealing past temperatures. Before the '70's, tree rings did mirror temperatures, but, after the middle of that decade, they diverged, and climatologists' emails recommended playing down tree ring reliability, just as thess "researchers" are saying. Yet the anti-climate change "nay-sayers" denounced them!
NotParker
2 / 5 (8) Feb 05, 2012
Tree rings stopped working in 1960. And never had worked before 1550. That data was deleted by dishonest fraudsters.

Which means tree rings never worked as a proxy for temperature.

Climate Frauds just kept lying about it.

http://climateaud...3/13321/
Vendicar_Decarian
0.6 / 5 (40) Feb 05, 2012
Wow.. According to denialist Parker Tard, tree rings correlate with temperatures for a period shorter than the calibration time of the data.

What a moron....

"Tree rings stopped working in 1960. And never had worked before 1550." - ParketTard

"That data was deleted by dishonest fraudsters." - Parker Tard

In other words you are saying that a cabal of scientists broke into universities and libraries all over the world and cut out pages of research that claimed the opposite of your claim.

Sorry Tard Boy, but such things only happen in tired anti-scientific minds of lying conservatives like yourself.

Can you explain to us Parker Tard why your own reference shows good correlation for 400 years, and not the 10 years you just claimed?

You wouldn't be lying again would you?
Ronan
5 / 5 (1) Feb 06, 2012
Vendicar Decarian, one possible explanation is that he never claimed that they show good correlation for only ten years. He said 1550, not 1950, giving a time span of 1550-1960--about four hundred years.
Parsec
3 / 5 (6) Feb 06, 2012
When you're working to promote a lie, it can be helpful to have support among "collegaues". The "researchers" pushing that the Little Ice Age began four centuries before it did were stymied by the existence of disagreeing information. Such as that tree tings did not show such temperature drops. So they cobbled together the fiction that tree rings do not accurately reflect temperature. Then the present that as a "separate" "discovery" and use it to maintain the claim for the early beginning of the Little Ice Age.

I so love conspiracy theorists. This article is talking about a few years discrepancy, in 3 different massive volcanic events. A few years doesn't wipe out 400 years of data.

Can you hear everyone laughing at you? You might need to remove your tinfoil hat to hear it.
Shootist
3 / 5 (6) Feb 06, 2012
Wow.. According to denialist Parker Tard, tree rings correlate with temperatures for a period shorter than the calibration time of the data.

What a moron....


Are you a child or do you just act like one on physorg?
NotParker
1 / 5 (3) Feb 06, 2012
Lets say you claim trees are a proxy for temperature. And you claim they match the temperature record from 1850 (when modern thermometers came into being in enough places) all the way to the present.

And then it turns out you lied. The proxies went down starting in 1950 when supposed temperatures went up.

That means the proxies either never work and 1850 to 1950 were a fluke or they underestimate temperature 30% of the time.

If the latter is true then there could be 300 years in the last 1000 that were warmer than today.

But NOOOOOOOO. Mann and his cohorts claim today was the warmest period in the last 1000 using bogus proxies.
NotParker
1 / 5 (3) Feb 06, 2012
The climate audit article shows that inconvenient data was deleted post-1950 and pre-1550 to hide the decline.

A proxy that does not match thermometers after 1950 is not a good proxy. A proxy that does no match other proxies before 1550 is not a good proxy.

Scientists who hide data that proves their proxy a failure are frauds.
Vendicar_Decarian
0.3 / 5 (36) Feb 06, 2012
Lets say that the Parker Tard invents a straw man and everyone identifies him as a liar and a fool for doing so.

"Lets say you claim trees are a proxy for temperature. And you claim they match the temperature record from 1850 (when modern thermometers came into being in enough places) all the way to the present." - Parker Tard
Vendicar_Decarian
0.3 / 5 (36) Feb 07, 2012
"A proxy that does not match thermometers after 1950 is not a good proxy." - Parker Tard

That is why tree rings are supplemented by isotopic ratio's, sea shell growth rates, borehole temperature measurements, sediment deposition rates, written historical records, etc. etc. etc.

"Scientists who hide data that proves their proxy a failure are frauds." - ParkerTard

I know of no scientists who have done such a thing, but we do know that denialists such as yourself are engaged in a never ending campaign of fraud and outright lies.

Do you intend to remain a fool and a liar for the rest of your life?
Vendicar_Decarian
0.3 / 5 (36) Feb 07, 2012
Where did Climate Audit get the data to show this if it was deleted as you have dishonestly claimed?

"The climate audit article shows that inconvenient data was deleted post-1950 and pre-1550 to hide the decline." - Parker Tard

Or is Climate Audit continuing to just make things up as they go along?
NotParker
1 / 5 (3) Feb 07, 2012
Where did Climate Audit get the data to show this if it was deleted as you have dishonestly claimed?


Read about it here:

http://climateaud...decline/

NotParker
1 / 5 (3) Feb 07, 2012
That is why tree rings are supplemented by isotopic ratio's, sea shell growth rates, borehole temperature measurements, sediment deposition rates, written historical records, etc. etc. etc.


Funny you should say that Vendicam ....

"A paper published this week in the journal Climate of the Past analyzes an "unprecedentally large network of temperature...proxy records" [a total of 120] and concludes that warming of the 20th century was "within the range of natural variability over the last 12 centuries."

Only two of the eight types of temperature proxies analyzed indicate 20th century warming exceeded that of the Medieval Warming Period."

http://hockeyscht...ing.html
rubberman
5 / 5 (2) Feb 07, 2012
Again with the MWP like it supports a denialist argument, when in fact the similarity is the reason for worry. World population at the onset of the MWP 70 million, humans as a source of GHG....almost none. World population today 7 billion, humans as source of GHG (outside of water vapour) bigger than all the rest for now. The warming may be within the range of natural variability when compared to the other
times in human history warming of this nature has been recorded, but our activities are severely amplifying what "might" have been at one time natural. Only an ignorant "TARD" would think we have no impact.
Vendicar_Decarian
0.3 / 5 (36) Feb 07, 2012
"Read about it here:" - Parker Tard

Your own reference shows that you are a liar when you claim that the data was deleted.

Do you intend to be a liar for the rest of your life Parker Tard?

Vendicar_Decarian
0.3 / 5 (36) Feb 07, 2012
"within the range of natural variability over the last 12 centuries." - Parker Tard

Let us know when the paper is accepted by the rest of the scientific community Tard Boy.

The paper you reference shows the standard two sigma error for the proxies at about. plus or minus 0.5'C. Current global temperatures are now around .74'C above historical averages.

Climatologists have pegged the limit of natural variability over hundreds of nominal years as being about 0.5'C in line with the proxi data from your reference.

Your failure is your conclusion that you can invalidate a .74'C increase in temperature based upon proxi data that has an error of plus or minus 0.5'C

There is simply insufficient accuracy in the long term proxi data to distinguish a 0.24'C rise above the noise floor.

You also have a deep desire to ignore the following sentence from your own reference....

Cont...
Vendicar_Decarian
0.3 / 5 (36) Feb 07, 2012
"However, our results show the rate of warming from the 19th to the 20th century is clearly the largest between any two consecutive centuries in the past 1200 yr." - Parker Tard's Reference.

Finally, your reference is a North American study. Not a global one, and is principally constrained to temperatures over land so comparison with the Land/Ocean temperature index is misleading as increases in Ocean temperature lag increases in land surface temperatures.

Your reference - a meta analysis of existing proxy records - does show some worth while results though, in that it illustrates how the error bars on the proxi records are slowly being reduced over time.
NotParker
1 / 5 (3) Feb 07, 2012
"However, our results show the rate of warming from the 19th to the 20th century is clearly the largest between any two consecutive centuries in the past 1200 yr."


Well Duh. The Little Ice Age was the coldest period in 10,000 years.

Go from the coldest period in this interglacial to the 5th warmest period after the Holocene Optimum, Minoan Warming, Roman Optimum and MWP and it might appear a large jump.

"Temperatures in Greenland were about 1.5 C warmer 1000 years ago than now.

It was perhaps 2.5 C warmer 4000 years ago.

The period around 1875, at the lowest point of the Little Ice Age, marked the coldest point in the last 10,000 years."

http://notalotofp...0-years/
Vendicar_Decarian
0.3 / 5 (36) Feb 08, 2012
About 0.2'C cooler than the baseline average global temperature. Current temperatures are now 0.74'C above that baseline.

From your own reference.... "Little Ice Age Coldest Period In The Last 7000 Years In Greenland"

You seem to have magically left out the "in greenland" part.

Did you feel a need to tell yet another lie of omission?

"Well Duh. The Little Ice Age was the coldest period in 10,000 years." - Parker Tard

"Go from the coldest period in this interglacial to the 5th warmest period after the Holocene Optimum..." - Parker Tard

As the following graphic shows, it has been a remarkably rapid increase in temperature, and from one of your own references the fastest increase since the end of the last period of glaciation.

http://en.wikiped...ison.png

Vendicar_Decarian
0.3 / 5 (36) Feb 08, 2012
Greenland isn't the entire globe.

Why do you feel a need to constantly misrepresent the truth Tard Boy?

Do you intend to be a liar for the rest of your life? I have news for you. You are pathetic at it.

"Temperatures in Greenland were about 1.5 C warmer 1000 years ago than now." - Parker Tard

"The period around 1875, at the lowest point of the Little Ice Age, ..." - Parker Tard

It is common knowledge that the standard pattern of temperature recovery after glaciation is an overshoot of global temperatures past equilibrium as a result of the outgassing of CO2 from the warming ocean.

This overshoot is followed by a slow decline in temperatures over the interglacial period to the start of the next glacial cycle. This decline is punctuated with various short term fluctuations principally driven by changes in terrestrial volcanism.

As always Parker Tard, you show less intelligence and less honesty than the can of soup that I had for dinner.