In article ,
Nad R wrote:

Doug Freyburger wrote:

It's an issue not handled in the currect discussion. While the fact of
global warming completely real it demonstrates that our current century
is not the warmest of recent times. It demonstrates that the records
cited do not go back as far as climate records in general. It also

If there are no temperature records of the past, how do yo know that our
century is not the warmest century in "human" history?

Lipids in algae. Stay tuned.


demonstrates that degree of human causation is not the primary issue
because humans have done fine in centuries past that were warmer than
today. The primary issue is the social change triggered by climate
change and what to do about it. The history of Greenland makes it clear
that global warming has happened in the past without human input so it's
not about that. A point that Nad R hasn't gotten.

When has global warming happened in the past?

The planet has had ice ages due to volcanos and possible meteor impacts.
When the dust settled, the earth returned to normal temperatures. Because
the ice melted does not constitute a global warming, higher than normal
temperature..

Note: "faith" means believing in something in which all the facts are not
there.
Ex: I have "faith"I will find that hot looking woman and have a happy life

--
---------
http://www.youtube.com/watch?v=hYIC0eZYEtI
http://www.democracynow.org/blog/2011/3/7/michael_moore
http://www.youtube.com/watch?v=eZkDikRLQrw
http://www.youtube.com/watch?v=MyE5wjc4XOw

In article
,
Billy wrote:

In article ,
Nad R wrote:

Doug Freyburger wrote:

It's an issue not handled in the currect discussion. While the fact of
global warming completely real it demonstrates that our current century
is not the warmest of recent times. It demonstrates that the records
cited do not go back as far as climate records in general. It also

If there are no temperature records of the past, how do yo know that our
century is not the warmest century in "human" history?

Lipids in algae. Stay tuned.

Rats! The article has to do with rainfall, not temps. But still, it is
an interesting article that relates to gardening and agriculture.

Scientific American
March, 2011

A Shifting Band of Rain

By mapping equatorial rainfall since
A.D. 800, scientists have figured out how
tropical weather may change through 2100

By Julian P. Sacks and Conor L. Myhrvold

THE FIRST INDICATION THAT OUR EXPEDITION WAS NOT GOING AS PLANNED was
the abrupt sputter and stop of the boat's inboard engine at 2 A.M. The
sound of silence had never been less peaceful. Suddenly, crossing the
open ocean in a small fishing vessel from the Marshall Islands in the
North Pacific Ocean seemed an unwise choice. A journey to a scientific
frontier had led us to a different frontier altogether, a vast darkness
punctuated by the occasional lapping wave.

We are climate scientists, and our voyage (which ended safely) was one
of many intended to help us do what at first glance seems impossible:
reconstruct rainfall history back in time, across an ocean. By tracing
that history,we can gain a better understanding of how the ongoing
buildup of greenhouse gasses in the atmosphere, rising air temperatures
and changes in tropical precipitation are likely to alter future climate
patterns. We have traveled far and wide to numerous islands across the
Pacific Ocean.
-----
IN BRIEF
The tropical rain band that wraps the globe north of the equator
migrates as atmospheric temperature changes, altering rainfall patterns
worldwide.

Data from sediments in Pacific island
lakes show that the band is at 3°N
to 10°N, as far north as it has ever been in the last 1,200 years.

At current warming rates, the band could shift north by five degrees
by 2100, drying out farmland for millions of people in Ecuador,
Colombia, and elsewhere.

Multiyear drought conditions in the southwest U.S. could persist as that
area becomes more like the semiarid region of northern Mexico.
-----

Some present-day climate patterns are well known, such as the El Nino
and La Nina circulations in the Pacific. A lesser known but equally
important pattern is the primary precipitation feature on the planet: a
band of heavy rainfall that circles the globe in the tropics and
migrates north or south seasonally with the angle of the sun. The area
in which it moves is known as the Intertropical Convergence Zone (ITCZ).

Any change in the earth's temperature, as a result of incoming solar
radiation or greenhouse gases, can affect the rain band, which provides
the precipitation that feeds equatorial agriculture. The band also plays
a central role in the monsoons of Asia, Africa and India and the large
convection cells that transport heat from the equator toward the poles.
The frequency and intensity of El Nino and La Nina events and the
strength and duration of hurricane seasons in the Pacific and Atlantic
can all be influenced by variations in the band's position. Changes in
rainfall
resulting from a permanent shift of the band would dramatically alter
the equatorial environment, with effects reaching worldwide. And we have
good reason to believe the band is shifting.

Until recently, climate scientists did not know whether the current
annual range of the band's midline‹from 3°N to 10°N latitude over the
Pacific Ocean‹was its historical range. But now field measurements from
latitudes bracketing the ITCZ have allowed our colleagues and us to
define how the band has moved over the past 1,200 years. A large shift
of five degrees northward‹about 550 kilometers‹occurred from about 400
years ago until today. Discovery of that shift led us to a startling
realization: small increases in the greenhouse effect can fundamentally
alter tropical rainfall. We can now predict where the ITCZ will move
through 2100 as the atmosphere warms further. We can also predict
whether rainfall may rise or fall across the world's equatorial zones,
the probable effects across higher latitudes in Asia, Central America
and the U.S. southern tier, and what those changes might mean for
weather and food production. Some places are likely to benefit, but many
others, we fear, will face dry times.

MEDIEVAL UNKNOWN

UNTIL WE BEGAN mapping rainfall history, scientists had little data
about where the ITCZ had been during the past millennium. The band
hovers near the equator, but it can be tens or hundreds of kilometers
wide, depending on local conditions and seasonal sunshine. Because the
zone is highly pronounced over the Pacific, that region is ideal for
tracking its movement. And because the rain band girds the earth,
Pacific trends indicate global changes.

Scientists can profile the sun's strength from isotopes such as carbon
14 in tree rings and beryllium 10 in ice cores and can reconstruct the
historic profile of world-wide greenhouse gases from air bubbles trapped
in tubular cores of ice extracted from polar regions. By comparing solar
output and greenhouse gas levels with the ITCZ's position over
centuries, we can infer how tropical rainfall might change in the 21st
century in response to rising greenhouse gas emissions.

Clever investigators have identified many different indicators of global
temperature during the past millennium. Two periods stand out. Around
A.D. 800, global temperatures were similar to those in the late 1800s.
Temperatures then rose during the Medieval Warm Period (A.D.800 - 1200),
reaching levels similar to 20th-century temperatures. They gradually
settled and fell during the Little Ice Age (A.D. 1400-1850). In the past
two decades the sun's output has remained essentially constant, yet both
temperature and levels of carbon dioxide‹the most abundant manmade
greenhouse gas‹have become significantly higher than at any point in the
past 1,200 years.

Atmospheric scientists knew few specifics about past tropical climate,
however, when we began our work. Seafloor sediments, which can provide
exquisite records of climate on multithousand-year timescales,
accumulate too slowly to record much information about the past 1,000
years. Many corals produce annual bands, but the creatures rarely live
longer than 300 years, providing no records from 300 to 1,000 years ago.

Mapping rainfall would allow us to fill in the missing information about
the ITCZ's position over the past millennium. Usually determining
rainfall once it has hit the ocean is a lost cause. But small islands
scattered across the Pacific have enclosed lakes and ponds that can
reveal the history. In the past six years we have collected dozens of
sediment cores from the bottoms of such waters in some of the most
remote, exotic Pacific islands. The locations span a range of latitudes
above, below and within the current band and fully across the Pacific.
We can define where the rain band was during a given time period by
pinpointing places that experienced intense rainfalls in that period at
various latitudes. Simultaneous rainfall increases and decreases,
northward or southward, indicate a common, oceanwide shift in the band.

Fieldwork is an adventure fraught with setbacks, equipment issues,
language barriers and difficulty getting to the sediment-coring
locations. For example, by the time we arrived in the capital city of
Majuro, the local airline, Air Marshall Islands (affectionately known to
locals as "Air Maybe"), had two broken planes in its fleet of two. The
two-day trip mentioned earlier to test a local entrepreneur's modified
fishing boat that looked alarmingly unseaworthy ended when the engines
died on our overnight return from a neighboring atoll.

To retrieve an undisturbed sediment core, we push, pound and screw long
tubes into a lake's bottom. Just about every site we have cored has a
unique sediment sequence. Sometimes we find bright-red gelatinous layers
several meters thick made up of cyanobacteria, as in the Washington
Island lake. Other times the sediment is brown mud rich in hydrogen
sulfide (read: it stinks!), containing mangrove leaf fragments and the
occasional layer of bivalve shells, as in Palau.

As we slog through mud on foot and row across shallow water, we push a
long pole into the sediment to test depths and to see whether obstacles
lurk. It is not unusual to abort a core attempt because it hits rocks,
ancient coral, sand or roots.

Because the rate of sediment deposition is highly variable, we do not
know how deep we need to go. Generally speaking, one meter of sediment
stretches back at least several hundred years: nine meters of sediment
from Washington Island, for example, spanned 3,200 years. When possible,
we try to hit "bedrock" at the bottom of a co deposited sand, coral
or volcanic rock marking the time when the lake first began accumulating
sediment, so that we can obtain the most complete record of the
historical climate.

THE SECRET LIES IN LIPIDS

RECONSTRUCTING RAINFALL is our goal, but we have to measure the
ecosystem's characteristics in the present climate to know what the same
measurements of the past environment reveal about the past climate. We
therefore collect water samples at different depths to determine the
chemical composition and hydrogen isotope ratio of the water, as well as
traits of the algal and microbial populations. We trap phytoplankton,
zooplankton and microbes on fine, glass-fiber filters, then immediately
store them on ice so we can later analyze their lipid composition.
Vegetation samples are collected from the immediate vicinity to evaluate
their lipids, too.

After we carefully raise the cores out of the lake bottom, we have to
get the samples back to the lab without disturbing the sediment. To
avoid mixing a core's layers, we painstakingly "section" the uppermost
sediments that are particularly soft into one-centimeter slices and
store each slice in labeled plastic bags.

Once we have sectioned cores on site, we journey back to Seattle to our
lab at the University of Washington, hauling stacks of ice chests filled
with sediment and water and long cardboard boxes filled with the
segments of cores that did not require bagging. By measuring the two
stable isotopes of hydrogen in the lipids of algae preserved in
successively deeper layers of sediment, and dating the samples back in
time, we can infer the amount of rainfall that occurred when the flora
lived [see box on opposite page].

WET REGIONS BECOME DRY

OVER SUCCESSIVE YEARS we have added more data to an increasingly
accurate map thai pinpoints the ITCZ's historical locations, and we
continually update it with our latest results. Although our findings
from the most recent expedition‹to Kosrae in Micronesia‹will take a few
more months to analyze, the results from many trips, : combined with
data from colleagues, indicate that small changes in atmospheric heat
were accompanied by large changes in tropical rainfall during the Little
Ice Age, drying previously wet regions such as Palau and bringing
abundant rain to previously arid regions such as the Galapagos Islands.
When solar energy reaching the top of the atmosphere decreased by just
two tenths of a percent for about 100 years, the ITCZ migrated south
toward the equator by 500 kilometers.


That sensitivity does not bode well for our future. The
Intergovernmental Panel on Climate Change projects that because of
primarily tailpipe and smokestack emissions, the atmospheric carbon
dioxide concentration will rise to double pre-industrial levels by
mid-century and triple by 2100, causing an increase in atmospheric
heating two to three times larger than changes that occurred at the end
of the Little Ice Age from increased sunlight alone.

During the Little Ice Age the rain band's midline remained south of 5°N.
Today it hovers between 3°N and 10°N. Recent increases in greenhouse
gases threaten to move the band's center another five degrees
northward‹550 kilometers‹by 2100. This new location (8°N to 15°N) would
significantly change the intensity of rainfall in many regions [see box
on opposite page}.

Evidence for potential changes comes from our findings on the islands.
Washington Island, located at 5°N, now receives three meters of rain a
year, but 400 years ago it received less than one meter of rain and
experienced more intense evaporation. Conversely, the highlands of San
Cristobal Island at 1°S in the desertlike Galapagos archipelago were
substantially wetter during the Little Ice Age.

Evidence from archaeologists is also helpful. They have concluded that
on islands across Indonesia and the South Pacific, a marked increase in
the construction of fortifications coincided with the last large
southward shift in the ITCZ's position. The bulk of fortifications‹stone
structures to fend off intrusions from neighboring societies‹were built
from the onset to the end of the Little Ice Age. As the rain band moved
south, islands left in its northern wake dried out, perhaps forcing
inhabitants to flee to more southern islands, raising fears of invasion
among local peoples there.

Today desalination technology and shipping ease strict dependence on
rainfall, but a move of the rain band five degrees further north would
endanger the hundreds of millions of people who live near the equator
and depend on subsistence agriculture, not to mention tropical
biodiversity. Most nations in the current range are developing nations.
They are likely to experience great population increases during this
century and are unlikely to have the resources to successfully adapt.
Rainfall declines, on one hand, and flooding, on the other, across
decades or even a few years would reduce crop yields, leading to
localized food shortages, political unrest and ultimately geographic
displacement.

Areas directly in the ITCZ for the first time (10°N to 15°N), such as El
Salvador and Manila in the Philippines, would receive more rain annually
and would become more humid. Regions no longer under the
rain band's direct influence (3°N to 8°N) would receive less rain and
become more arid. Whether this drying effect would be countered in
certain places by the strength of the Asian and Indian monsoons is
subject to debate.

LESS COFFEE, FEWER BANANAS OVERALL, WET AREAS in northern
Indonesia,Malaysia, the Philippines, Micronesia, Thailand and Cambodia
would miss a good portion of the ITCZ rains they now receive. Crop
varieties ideal for today's growing conditions would no longer thrive.
For example, coffee plants, much like vineyards, need a lot of rain at
the beginning of the growing season and require more than 1.8 meters in
total to develop suitable beans.

In Central America, Ecuador and Colombia would be left in the ITCZ's
wake and become drier. Colombia's increased urbanization may help it
cope because its economy is no longer as highly dependent on
agriculture. Colombia, however, is the world's third-largest coffee
producer, and as in Indonesia, less precipitation could affect long-term
coffee yields. Most growing regions for the bean, which are below 8°N
latitude, would likely suffer by the mid- to late 21st century.
Productive areas in the south and along the coast are most at risk
because they will be the farthest from the rain band.

The future of Ecuador's banana industry may be bleak. Good bananas
require warm temperatures and 2 to 2.5 meters of annual rainfall, but
Ecuador is already well below the current ITCZ and barely meeting the
minimum precipitation threshold. A shift would likely decrease rainfall
to a meter a year or less by 2100, shutting down the country's banana
industry. A large drop in banana yield can happen quite fast. In the
Philippines at the beginning of 2010, roughly half of the plantations
produced small and underweight bananas that were useless commercially,
because of an abnormal dry season.

Subsistence agriculture would also be affected in all the aforementioned
locations. Even if people gravitate toward cities, a lack of regional
food sources is a recipe for disaster.

If the band continues migrating north at the average rate it has been
over the past 400 years, substantial rainfall changes in the continental
U.S. are
likely, too. Some changes may have already begun. The south-western U.S.
is enduring a severe multiyear drought that is likely to represent the
new normal pattern in the 21st century should greenhouse gas levels
continue to rise apace. Higher temperatures, and a continuing northward
shift of the rain band, threaten to shift the subtropical dry zone that
lies to its north, which currently stretches across northern Mexico,
into this part of the country.

Scientists are unclear whether a northward shift would affect the
frequency or size of hurricanes or monsoons. We also have yet to
determine any possible effects on the patterns of El Nino and La Nina.

BETTER MODELS COMING

MORE WORK needs to be done before alarm bells can be sounded with
confidence. Computer-based climate models have not accurately reproduced
past and present rainfall patterns in the tropics. If modelers
can use data from sediment cores and other sources to produce patterns
that more closely approximate those that are known, the world could have
greater confidence in their projections of future rainfall. This type of
experiment is being pursued by our colleagues at the University of
Washington and elsewhere.

We will continue to study sediments from tropical islands in the ITCZ,
and to its north and south, to more precisely define the rain band's
position throughout the past millennium and to predict where it will be
in generations to come.

MORE TO EXPLORE :

Proxy-Based Reconstructions of Hemispheric and Global
Surface Temperature Variations over the Past Two Millennia.
Michael E. Mann et al. in Proceedings of the National
Academy of Sciences USA, Vol. 105, No. 36, pages 13252-13257;
September 2,2008.

Southward Movement of the Pacific Intertropical Convergence
Zone AD 1400-1850. Julian P. Sachs et al. in Nature
Geoscience, Vol. 2, No. 7, pages 519-525; July 2009.

Paleoclimates and the Emergence of Fortifications in the
Tropical Pacific Islands. Julie S. Field and Peter V. Lape in
Journal of Anthropological Archaeology, Vol. 29, No. 1, pages
113-124; March 2010.

Paleoclimate research at the Sachs Lab:
http://faculty.washington.edu/jsachs

Illustration by George Retseck (globes) and Jen Christiansen (graph)
--

Algae: Rain Gauge of the Ages

Algae obtain all their hydrogen from the water in which they live.
By measuring the two stable isotopes of hydrogen‹deuterium
and protium‹in the lipids of algae that are preserved in sediment
underneath tropical lakes, we can infer the amount of rainfall that
occurred when they lived.

The deuterium/protium (D/H) ratio of many algae has a linear
relation with the D/H ratio of the water. The water ratio, in turn,
reflects the rate of precipitation relative to evaporation in a lake's
area. Within the tropical rain band region, where rainfall is frequent
and heavy, the D/H ratio of lake and seawater is low. Outside
the region, where evaporation can exceed precipitation, the
D/H ratio is high. So we can use the varying D/H ratios of algal
lipids found deeper and deeper in sediment to infer past rainfall.

Fortunately for us, algae also adjust the D/H ratio of their lipids
in response to salinity. Special conditions on Christmas Island
created a natural experiment for us to calibrate this response. The
island hosts a series of ponds that have similar temperatures, light
levels, nutrient levels and water D/H ratios, yet they differ widely
in their salinities. We found that as the salinity increased so did the
D/H ratio of lipids produced by cyanobacteria, in a linear fashion.
Because the salinity of sal****er ponds decreases when rain is
abundant and increases when it is dry, the salinity effect on lipid
D/H acts in the same direction as the rainfall amount effect,
making lipid D/H ratios sensitive gauges of hydrologic change.

These results, alone, are like geeks at the prom: they need
dates! A sediment's age is determined by two radioactive isotopes,
carbon 14 and lead 210, which have half-lives of 5,730 and
22.3 years, respectively. By comparing the hydrogen isotope ratios
at various dates, we have reconstructed the series of precipitation
changes going back 1,200 years. ‹J.P.S. and C.LM.




demonstrates that degree of human causation is not the primary issue
because humans have done fine in centuries past that were warmer than
today. The primary issue is the social change triggered by climate
change and what to do about it. The history of Greenland makes it clear
that global warming has happened in the past without human input so it's
not about that. A point that Nad R hasn't gotten.

When has global warming happened in the past?

The planet has had ice ages due to volcanos and possible meteor impacts.
When the dust settled, the earth returned to normal temperatures. Because
the ice melted does not constitute a global warming, higher than normal
temperature..

Note: "faith" means believing in something in which all the facts are not
there.
Ex: I have "faith"I will find that hot looking woman and have a happy life

--
---------
http://www.youtube.com/watch?v=hYIC0eZYEtI
http://www.democracynow.org/blog/2011/3/7/michael_moore
http://www.youtube.com/watch?v=eZkDikRLQrw
http://www.youtube.com/watch?v=MyE5wjc4XOw