PLEASE NOTE:


*

CCNet CLIMATE CHANGE & CLIMATE SCARES, 18 January 2001
------------------------------------------------------


"The transition of our world from a temperate into a glacial state
is one of the most worrying potential impacts of climate change. It is
imperative that we understand exactly how stable our current climate is
and what could trigger another ice age."
--Nature, 11 January 2001


"Fresh doubt has been cast on evidence for global warming following
the discovery that a key method of measuring temperature change has
exaggerated the warming rate by almost 40 per cen."
--Robert Matthews, The Sunday Telegraph, 14 January 2001


"Is Antarctic Peninsula warming identified with "Global warming"?
No, not by BAS scientists who prefer to call the warming in the
Antarctic Peninsula a strong regional warming."
--Julian Paren, British Antartic Survey


(1) GLOBAL WARMING CLAIMS 'BASED ON FALSE DATA'
    The Sunday Telegraph, 14 January 2001

(2) CATASTOPHIC DROUGHTS MAY BE ANCIENT HISTORY IN THE FUTURE
    Anatta <anatta@UCAR.EDU>

(3) INCREASED CLOUD COVER BLAMED FOR COOLING TREND IN EASTERN U.S.
    Andrew Yee <ayee@nova.astro.utoronto.ca>

(4) WHERE'S THE HEAT?
    Junkscience, 16 January 2001

(5) RETREATING ICE SHELVES TRIGGERED BY WARMER SUMMERS, MELT WATER
    Andrew Yee <ayee@nova.astro.utoronto.ca>

(6) RETREATING ICE SHELVES: QUESTIONS AND ANSWERS
    British Antarctic Survey

(7) TO BLEACH OR NOT TO BLEACH: CORAL REEF RESPONSE TO GLOBAL WARMING
    CO2 Science, 17 January 2001

(8) ICE AGES & INSTABLITIES
    Nature Science Update, 11 January 2001

(9) COLD COMFORT FOR CLIMATE'S FUTURE
    Nature Science Update, 12 January 2001

(10) COMPUTER SPECULATION ABOUT RAPID CLIMATE CHANGES DURING THE LAST ICE AGE
     Nature 409, 153 - 158 (2001)

(11) WHAT TRIGGERS GLOBAL COOLING EVENTS?
     Nature 409, 171 - 175 (2001)

=================
(1) GLOBAL WARMING CLAIMS 'BASED ON FALSE DATA'

From The Sunday Telegraph, 14 January 2001
http://www.telegraph.co.uk/et?ac=004179367019210&rtmo=asppxJJL&atmo=rrrrrrrq&pg=/et/01/1/14/wglob14.html

By Robert Matthews, Electronic Telegraph 1/14/01

FRESH doubt has been cast on evidence for global warming following the
discovery that a key method of measuring temperature change has exaggerated
the warming rate by almost 40 per cent.

Studies of temperature records dating back more than a century have seemed
to indicate a rise in global temperature of around 0.5 ° C, with much of it
occurring since the late 1970s. This has led many scientists to believe that
global warming is under way, with the finger of blame usually pointed at
man-made pollution such as carbon dioxide.

Now an international team of scientists, including researchers from the Met
Office in Bracknell, Berkshire, has found serious discrepancies in these
temperature measurements, suggesting that the
amount of global warming is much less than previously believed.

The concern focuses on the temperature of the atmosphere over the sea, which
covers almost three quarters of the Earth's surface. While scientists use
standard weather station instruments to detect warming on land, they have
been forced to rely on the crews of ships to make measurements over the vast
ocean regions.

Crews have taken the temperature by dipping buckets into the sea or using
water flowing into the engine intakes. Scientists have assumed that there is
a simple link between the temperature of seawater and that of the air above
it.

However, after analysing years of data from scientific buoys in the Pacific
that measure sea and air temperatures simultaneously, the team has found no
evidence of a simple link. Instead, the seawater measurements have
exaggerated the amount of global warming over the seas, with the real
temperature having risen less than half as fast during the 1970s than the
standard measurements suggest.

Reporting their findings in the influential journal Geophysical Research
Letters, the scientists say that the exact cause of the discrepancy is not
known. One possibility is that the atmosphere responded faster than the sea
to cooling events such as volcanic eruptions.

The findings have major implications for the climate change debate because
the sea temperature measurements are a key part of global warming
calculations. According to the team, replacing the
standard seawater data with the appropriate air data produces a big cut in
the overall global warming rate during the last 20 years, from around 0.18¡C
per decade to 0.13¡C.

This suggests that the widely-quoted global warming figure used to persuade
governments to take action over greenhouse gases exaggerates the true
warming rate by almost 40 per cent. The team is
now calling for climate experts to switch from seawater data to sea-air
temperature measurements.

One member of the team, David Parker, of the Hadley Centre for Climate
Prediction and Research at the Met Office, said that the discovery of the
discrepancy "shows we don't understand everything,
and that we need better observations - all branches of science are like
that". Yet according to Mr Parker, the new results do not undermine the case
for global warming: "It is raising questions about the interpretation of the
sea-surface data."

Even so, the findings will be seized on by sceptics as more evidence that
scientists have little idea about the current rate of global warming, let
alone its future rate. Climate experts are still trying to explain why
satellites measuring the temperature of the Earth have detected little sign
of global warming - despite taking measurements during supposedly the
warmest period on record.

Some researchers suspect that the fault may again lie with the ground-based
temperature measurements. They say that many of the data come from stations
surrounded by growing urban sprawl, whose warmth could give a misleading
figure. A study of data taken around Vienna, Austria, between 1951 and 1996
found that the air temperature rose by anything from zero to 0.6¡C,
depending on precisely where the measurements were made.

Copyright 2001, The Daily Telegraph

===============
(2) CATASTOPHIC DROUGHTS MAY BE ANCIENT HISTORY IN THE FUTURE

From Anatta <anatta@UCAR.EDU>

2001-3
FOR IMMEDIATE RELEASE: January 16, 2001

Scientists Make Rain in Mexico

Contact:
Anatta
Telephone: 303-497-8604
Fax: 303-497-8610
E-mail: anatta@ucar.edu

BOULDER--Producing more rain by seeding clouds may no longer be wishful
thinking. After many failed attempts by scientists to duplicate
cloud-seeding experiments that appeared to have worked in the past, a team
from the National Center for Atmospheric Research (NCAR) believes they have
finally succeeded in increasing rainfall in existing storm clouds and
quantifying the results. The findings are being presented this week at the
American Meteorological Society's annual meeting in Albuquerque.

A recent three-year randomized experiment in the northern Mexican state of
Coahuila showed that rainfall from seeded clouds lasted longer, the rainfall
area was larger, and total precipitation was higher (sometimes even doubled)
than output from similar nonseeded clouds. In many cases the results of the
seeding were statistically significant 20 minutes to an hour after seeding.

The Mexico project was designed to repeat the success of a groundbreaking,
five-year effort conducted in South Africa in the early 1990s. The new
study, which followed several years of drought in northern Mexico, was
funded by the Mexican state of Coahuila with financial support from Altos
Hornos de Mexico, a private steel company. NCAR's primary sponsor is the
National Science Foundation.

NCAR researchers flew into the Mexican rain clouds in a Piper Cheyenne
twin-engine turboprop airplane, equipped with wing-mounted racks carrying 24
hygroscopic flares and an instrument package to measure basic cloud physics
indicators. The flares spewed salted smoke into the moisture-rich updrafts
entering the clouds from below. The tiny particles (a mixture of sodium,
magnesium, and calcium chlorides) attracted and absorbed the surrounding
water vapor to more readily create large drops heavy enough to fall out as
rain.

"We are very encouraged by the results," says lead scientist Roelof
Bruintjes of NCAR. However, the number of cases is marginal for any
statistical analysis, he adds. Funding for a planned fourth year of data
gathering was cut when the Mexican drought ended. This left the total number
of cases at 94, compared to 127 in the South Africa study. The team is
optimistic that more seasons in the field will extend the results and help
establish statistical significance.

Even more problematic is that scientists cannot fully explain how the
seeding process works inside the cloud. "We must be able to explain both
microphysical and dynamical responses of the cloud to the seeding
procedure," cautions Bruintjes, "before we can claim full success."

The main tool for "nowcasting" the weather and for evaluating the seeding
experiment was a 5-cm wavelength weather radar. Special software developed
at NCAR displayed the radar data and the aircraft position in real time for
directing operations. It also objectively identified storms for evaluating
the results.

NCAR is managed by the University Corporation for Atmospheric Research, a
consortium of more than 65 universities offering Ph.D.s in atmospheric and
related sciences.

Visuals: Images are available at ftp://ftp.ucar.edu/communications.
Filename(s): flaresvert.tif. Caption: Airborne hygroscopic flares emit
water-attracting particles into cloud updrafts. Photo courtesy of the
National Center for Atmospheric Research.

===============
(3) INCREASED CLOUD COVER BLAMED FOR COOLING TREND IN EASTERN U.S.

From Andrew Yee <ayee@nova.astro.utoronto.ca>

Lynn Chandler
Goddard Space Flight Center, Greenbelt, Md.          January 16, 2001
(Phone: 301/614-5562)

James E. Kloeppel
University of Illinois News Bureau, Urbana-Champaign, Il.
Phone: (217/244-1073)

Release No: 01-03

THE EASTERN U.S. KEEPS ITS COOL WHILE THE WORLD WARMS

Much of the Earth has warmed over the last half-century, but the eastern
half of the United States has shown a cooling trend. NASA-funded research
indicates cooler temperatures in the eastern U.S. are caused by an increase
in sun-shielding clouds produced by warmer ocean temperatures in the
Pacific.

Walter A. Robinson of the University of Illinois at Urbana-Champaign, James
Hansen of NASA Goddard Institute for Space Studies, and Reto Reudy of
Science Systems and Applications, Inc. will present these findings in a
paper entitled "Where's the Heat? Insights From GCM Experiments into the
Lack of Eastern U.S. Warming" at the American Meteorological Society Annual
Meeting in Albuquerque, N.M. on January 15.

Eastern U.S. temperatures have displayed a cooling trend of 0.1 degree
Celsius per decade, while global temperatures warmed by that same amount
from 1950 to 1997. The researchers used a computer climate model to see if
this regional cooling could be caused by changes in sea surface temperature.
Robinson said that in the GISS model, "Warmer sea surface temperatures in
the tropical Pacific cause greater cloud cover over the eastern United
States. This increased cloud cover is directly responsible for the cooling."
The brightness of a cloud causes a large percentage of incoming solar
radiation to be reflected back into space, thus keeping the atmosphere
cooler than if the cloud wasn't there.

Using the climate simulations, Robinson found the amount of water vapor in
the Gulf of Mexico follows closely the water vapor released by the warm sea
surface temperatures in the Pacific Ocean. Water vapor from the Pacific
moves east to the Gulf of Mexico and is then carried over the eastern U.S.
by the clockwise circulation around an Atlantic subtropical high pressure
system. When the water vapor arrives over the U.S. it condenses and
generates more cloud cover, allowing less solar radiation to reach and warm
the Earth's surface.

Robinson's research utilized the GISS (Goddard Institute for Space Studies)
"general circulation model," which simulates the circulation of the
atmosphere around the world and used sea surface temperatures from around
the globe.

In order to create a focus on sea-surface temperatures in the model runs,
three components that can contribute to warming or climate forcing, were
"fixed." These are aerosols (particles in the atmosphere), solar irradiance
or brightness, and greenhouse gases (such as carbon dioxide). Because these
factors were fixed, they can be ruled out as the cause of cooling in the
model, leaving only sea surface temperatures as a variable.

The GISS model used ocean temperature data over a 47-year span, from 1950 to
1997 and looked at global sea surface temperatures in different areas. The
model used temperatures from 20 degrees north to 20 degrees south, and from
each of those endpoints to each pole. The only time the model showed
significant cooling in the eastern United States was when the tropical
Pacific waters warmed.

For more information about the American Meteorological Society's 81st Annual
meeting, please visit the web site:
     www.ametsoc.org/AMS/meet/81annual/

=============
(4) WHERE'S THE HEAT?

From Junkscience, 16 January 2001
http://www.junkscience.com

Now even models suggest that warmer ocean temperatures induce more
evaporation, leading to more cloud formation and subsequent surface cooling!
This is one of the great problems with the enhanced greenhouse hypothesis -
the so-called positive feedback of increased evaporation (water vapor is the
major greenhouse gas) inevitably results in the negative feedback of
increased albedo (reflection of solar radiation) due to increased cloud
formation, damping rather than enhancing the negligible warming influence
possible from anthropogenic atmospheric CO2 addition. Parenthetically, this
piece alludes to a global decadal trend of +0.1°C since 1950 although such a
figure is extremely dubious. The contiguous US composite record makes a fair
to muddling proxy for global temperature trends over the period, so judge
for yourself. Hard to pick a decadal trend of +0.1°C since 1950 isn't it?
These fanciful figures are enabled by using estimates of proxies for air
temperature. Over 7-10ths of the Earth's surface is composed of the oceans,
this means using ocean 'surface' temperatures (everything from 'bucket on a
rope' to ships' engine coolant water manifold temperatures) as a proxy for
air temperature. If you think this might be a less-than-reliable means of
establishing Earth temperature trends you are not alone.

=============
(5) RETREATING ICE SHELVES CAUSED BY WARMER SUMMERS & MELT WATER

From Andrew Yee <ayee@nova.astro.utoronto.ca>

Lynn Chandler
Goddard Space Flight Center, Greenbelt, Md.          January 16, 2001
(Phone: 301/614-5562)

Release No: 01-07

ANTARCTIC ICE SHELF COLLAPSE IS TRIGGERED BY WARMER SUMMERS, MELT WATER

Warmer surface temperatures over just a few months in the Antarctic can
splinter an ice shelf and prime it for a major collapse, NASA and university
scientists report in the latest issue of the Journal of Glaciology.

Using satellite images of tell-tale melt water on the ice surface and a
sophisticated computer simulation of the motions and forces within an ice
shelf, the scientists demonstrated that added pressure from surface water
filling crevasses can crack the ice entirely through. The process can
be expected to become more widespread if Antarctic summer temperatures
increase.

"The importance of melt water implies that ice shelf stability may not be
limited by the mean annual temperature, as has long been thought, but by the
mean summer temperature," says co-author Christina Hulbe of the University
of Maryland and NASA's Goddard Earth Science & Technology
Center. "As the mean summer temperature exceeds 0 degrees Celsius, surface
melting is likely to promote ice-shelf retreat."

The team of scientists -- Ted Scambos and Jennifer Bohlander of the National
Snow and Ice Data Center at the University of Colorado, Mark Fahnestock of
the University of Maryland, and Hulbe -- focused on the Larsen Ice Shelf on
the Antarctic Peninsula, which experienced major retreats in 1995 and 1998.
Over 775 square miles (2000 square kilometers) of the northern section of
this ice shelf disintegrated in January 1995 during a storm.

"This result implies that other ice shelves are closer to the breaking point
than we previously thought," says Scambos. "The shelf retreats that have
occurred so far have had few consequences for sea-level rise, but breakups
in some other areas, such as the Ross Ice Shelf, could lead to increases in
ice flow off the Antarctic and cause sea level to rise."

The floating ice shelves, which account for about 2 percent of all Antarctic
ice, typically undergo cycles of advance and retreat over many decades. It
has long been recognized that melt water filling of crevasses could enlarge
the cracks, but this study is the first to connect the basic physics of that
process with significant effects of surface melt ponds on ice-shelf
viability. The extra outward pressure of the water counteracts the internal
pressure holding the ice together.

Crevasses routinely form at the landward side of the shelf as glacial ice
pushes past coastal features and flows into the floating ice. The crevasses
slowly travel seaward as the ice shelf grows.

Satellite observations of melted water on the ice surface provided an
important clue to the water-pressure theory. Analyzing images of the Larsen
Ice Shelf over the past 20 years, Fahnestock found that the years with the
longest duration of surface melt water were also the years of major shelf
breakup events. The "melt season" during the major retreat year of 1995, for
example, was over 80 days long, about 20 days longer than average.

To find out if the accumulated melt water "wedge" could split a crevasse to
the bottom of the ice, Hulbe used a computer model to simulate the
thermodynamics of a northern section of the Larsen Ice Shelf before and
after the major retreats of the 1990s. Depending on the internal strength of
the ice, a water-filled crevasse just 15-50 feet (5-15 meters) deep could
fracture through the 220-yard (200-meter) thick ice shelf. The splintered
remains are probably held together by bridges between crevasses until a
combination of winds, tides, and another season of melting lead to a
breakup.

"We need to monitor the summertime temperatures to see what the future holds
for these ice shelves," says Hulbe. While some areas of the Antarctic have
warmed by as much as 2.5 degrees Celsius in the last 50 years, few records
have been kept of seasonal temperatures over ice shelves.

"In the past, researchers thought the Rose Ice Shelf area was up to 20
degrees below the climatic limit and therefore very stable," says Scambos.
"Our initial look at summertime temperatures there shows it is just a few
degrees below what we think is the threshold for surface ponding."

More information can be found at:

     http://www.gsfc.nasa.gov/gsfc/earth/environ/ice/ice.htm

"The Link Between Climate Warming and Break-up of Ice Shelves in the
Antarctic Peninsula," Scambos, T.A., Hulbe, C., Fahnestock, M., and
Bohlander, J. Journal of Glaciology, vol. 46, no. 154, pp. 516-530.

================
(6) RETREATING ICE SHELVES: QUESTIONS AND ANSWERS

From the British Antarctic Survey
http://www.nerc-bas.ac.uk/public/info/iceshelf.html

Questions and answers from the British Antarctic Survey. Prepared by Dr
Julian Paren, Director's Assistant in January 1998 in response to media
coverage on the potential loss of the Larsen B Ice Shelf and the impact of
such an event on the global climate system.

*Is the Antarctic warming significantly?

In general, no. Only the Antarctic Peninsula is warming throughout the year
at a rate that statisticians call "significant". Elsewhere in Antarctica
annual temperatures are fluctuating. There is evidence of warming at some
coastal sites and cooling at the South Pole but such trends are not decisive
enough for statisticians to term the changes "significant". In East
Antarctica one station at 140 E longitude has experienced a significant
warming but just in the winter season.

*Is the Antarctic Peninsula warming significantly?

Yes, this small part of the Antarctic has warmed by 2.5 degrees Centigrade
since the 1940s. Significant warming has occurred in all the seasons of the
year and the average annual temperature increase is statistically
significant. There has been a high interannual variability of temperature
which BAS meteorologists seek to understand. They see some connections of
the local climate with El Niño. The warming trend nevertheless is
unexplained.

*Is Antarctic Peninsula warming identified with "Global warming"?

No, not by BAS scientists who prefer to call the warming in the Antarctic
Peninsula a strong regional warming. They say this because no Global
Circulation Model predicts that the region should be oversensitive to
changes in greenhouse forcing. However this could be just a failing of the
current suite of Global Circulation Models which one could argue are not
detailed enough to simulate the climate of the region. The GCMs all differ
in their predictions of the pattern of change expected in the Antarctic next
century. None predict an unusually high warming localised in the Antarctic
Peninsula. Professor John Houghton (Chairman IPCC, Panel 1) on the Today
Programme (29-01-1998)called the Antarctic warming a " symptom" of global
warming. He failed to comment that the majority of Antarctica has had a
stable climate this century.

*Are ice shelves disintegrating in the Antarctic?
Yes, but only in the Antarctic Peninsula. This is the region that has warmed
by 2.5 degrees Centigrade since 1940, and is the one region of the Antarctic
where summer temperatures exceed 0 Degrees Centigrade. The infilitration of
melt water is seen as an important element in the disintegration of ice
shelves. As temperatures have warmed so (according to BAS scientists) the
viability of ice shelves moved southwards. Thus, the most northerly ice
shelves existing today are at risk from irreversible disintegration. We do
not know for how long ice shelves have been disintegrating in the Antarctic
Peninsula nor do we know accurately temperatures in the area before the
1940s. The information that Larsen B Ice Shelf is vulnerable to decay has
been well publicised. Its nearest northerly neighbour, Larsen A,
disintegrated in 1995.

*What do we know about Larsen B Ice Shelf?
BAS scientists in collaboration with Argentinian and German scientists have
been studying the Larsen Ice Shelf by a range of techniques. This includes
ice depth sounding by radar mounted on aircraft and analysis of satellite
images. The objective is a detailed computer model of the flow and fracture
of the ice shelf to enable predictions to be made of its future behaviour.
This work is ongoing and a real challenge to applied mathematicians. A time
scale for its eventual demise is the objective. The Larsen B Ice Shelf is
still in place.

*What effect will the disintegration of Larsen B have on the rest of
the environment?

When the Larsen B Ice Shelf disintegrates it will have little effect on two
accounts. Sea level will rise only if the ice held back by the ice shelf
flows more quickly onto the sea. In fact there is very little grounded ice
behind the ice shelf. The melting of an ice shelf (or turning it into a mass
of icebergs) has no impact on sea level. The loss of Larsen B cannot
influence global ocean circulation on any major scale. There can be no talk
of the alteration of the Gulf Stream from the loss of such minor ice
shelves. Scientists are still trying to detect the impact on the
glaciological and oceanic environment of the loss of the ice shelves which
have already occurred this century in the Antarctic Peninsula.

*What is the truth about the Gulf Stream then?

The circulation of the Atlantic is a result of many interactions between
water and the atmosphere and between water and ice. A key element of the
circulation is the sinking of surface waters at each end of the Atlantic
conveyor, in the Arctic and Antarctic. It has been argued that if these
surface waters did not sink, the route of the Gulf Stream would be affected.
In the Antarctic the primary cause of sinking water is the formation of
Antarctic Bottom Water (ABW) which has its origins in surface water, formed
by the freezing of sea ice, sinking under ice shelves and emerging as a
colder less saline Ice Shelf Water (ISW) which on further mixing becomes the
dense Antarctic Bottom Water (ABW). If ice shelves did not exist, then the
precursor for Antarctic Bottom Water could not exist. By Antarctic standards
the Larsen B Ice Shelf is a minor region where such processes could occur.
The threat to a markedly different Atlantic circulation would come if the
major ice shelf, Ronne-Filchner Ice Shelf, at the head of the Weddell Sea,
were to disappear. Is this likely?

*What can be said about the disintegration of other major ice

shelves and a future threat to the UK climate?
Extrapolating from the disintegration of Larsen A and other northerly ice
shelves to the important ice shelves of Antarctica is difficult indeed. They
have not experienced warming as yet. There is no indication that warming
trends in the Antarctic Peninsula will be maintained, or spread to areas
with a stable climate. Even so, the major ice shelves have average summer
temperatures around -10 degrees Centigrade; a full 10 degrees Centigrade
rise in temperatures before surface melting could herald in a threshold for
disintegration. A climate warming of 10 degrees Centigrade is outside any
predictions for a future Antarctic climate considered by the
Intergovernmental Panel on Climate Change (IPCC). If current warming in the
Antarctic Peninsula were maintained and the warming spread further over the
Antarctic, 200 years would be needed. This is a minimum time for change,
since neither eventuality appears likely.

Sea temperatures are also affected by climate warming. Before 10 degrees
Centigrade of warmth have occurred the sea temperatures around the largest
ice shelves could have risen enough to change the concentration of sea ice
and the characteristics of the water that ultimately lead to the production
of Antarctic Bottom Water. Experiments undertaken by British Antarctic
scientists using equipment installed beneath the Ronne Ice Shelf have
suggested that the bases of the ice shelves will melt less as the sea water
warms adjacent to the ice shelf. A warming ocean could lead to thickening
ice shelves because of reduced melting at their base and enhanced snowfall.
This process would postpone beyond 200 years the minimum time for
irreversible change.

British scientists with international collaborators are currently aboard HMS
Endurance studying the oceanographic conditions adjacent to Ronne Ice Shelf
with a view to increasing an understanding of the ocean circulation beneath
ice shelves and its feedback into the global ocean circulation. Such studies
confirm that there can be no simple extrapolation of events in the warmest
sector of the Antarctic to the ice shelves that dominate the Antarctic
environment and which dictate to some degree ocean circulation worldwide.

*If the continuing disintegration of Larsen Ice Shelf is inevitable
and has little impact on the global environment, why is it the object of
detailed study?

To date, the disappearance of ice shelves has been linked to the presence of
summer melt water which raises the internal temperatures of the ice shelves.
The direct cause/effect link has been inferred but not proved. By studying
all aspects of the flow and internal workings of the Larsen B Ice Shelf,
which is available to study, a more mechanistic understanding should emerge
of the processes which modify the size and structure of the ice shelf. The
basic physics involved can then be applied elsewhere. Larsen B Ice Shelf is
easily studied using the resources of the BAS Station at Rothera and the
Argentinian Station at Marambio.

*If you have further questions please address them to Dr Julian Paren,
British Antarctic Survey, High Cross, Madingley Road, Cambridge, CB3 0ET.
E-mail j.paren@bas.ac.uk.

===============
(7) TO BLEACH OR NOT TO BLEACH: CORAL REEF RESPONSE TO GLOBAL WARMING

From CO2 Science, 17 January 2001
(http://www.co2science.org/edit/v4_edit/v4n3edit.htm).

The massive El Niño of 1997-98, which pushed sea surface temperatures to
some of their highest levels of the past century, created a great stir among
students and aficionados of coral reefs.  It also raised a number of
concerns among many indigenous peoples who depend upon reef ecosystems for
their sustenance - either directly, via sea-life harvests, or indirectly,
via tourist-generated income - as near-synchronous mass coral bleaching was
observed to occur contemporaneously with the anomalous El Niño-induced
warming in several of the world's oceans.

Many environmentalists and media personalities equated this phenomenon with
the beginning of what they said would be the unavoidable end of CO2-induced
global warming, citing as evidence for their claims an impressive review of
the subject by Hoegh-Guldberg (1999).  However, their doomsday perspective
was challenged by the more optimistic assessment of Idso et al. (2000), who
conducted an equally rigorous review the scientific literature and concluded
that the predicted demise of the world's coral reefs was based on rather
tenuous evidence and that much remained to be learned before the dire
prognostication could be given any credence.

As the saga of the competing theories continues to evolve, the two ways of
looking at the issue continue to be elaborated.  In a report in the 1
December 2000 issue of Geophysical Research Letters, for example, Lough
(2000) provides additional support for the thesis of Hoegh-Guldberg.  In a
study of sea surface temperatures recorded at 47 coral reef sites around the
world, he shows that 1998 temperatures were the warmest of the past century,
and that the 1998 product of elevated temperature and its duration was fully
four times greater than previous high values recorded in 1983 and 1958.

In light of these observations, it is not surprising, Lough informs us, that
"during 1997-98 there were unprecedented numbers of reports of bleaching on
many of the world's coral reefs."  The implication that the bleaching events
were caused by the warm-temperature anomalies, however, is challenged by
Stone et al. (1999), who note "it is possible that mass coral reef bleaching
has been occurring unobserved throughout the last centuries [when it was
almost always much colder than it is now] but has only been noticed in
recent decades."  These researchers also suggest that the idea that the
recent bleaching event was fundamentally linked to global warming - which
provides a rising background temperature upon which El Niño warming spikes
are superimposed - "should be viewed more as an untested hypothesis,
supported so far only by circumstantial evidence."

Be that as it may, there is another aspect of the
global-warming/coral-bleaching debate that may be even more important than
whether elevated temperatures truly induce coral bleaching, which we are
willing to concede does indeed happen in many instances.  This other concern
has to do with what happens during and after bleaching events in terms of
resistance and response to prolonged episodes of elevated water temperature;
and it is this other half of the famed Shakespearian question we now
address.

In a recent study of the effects of the 1982-83 El Niño, Glynn et al. (2000)
observed that warming-induced coral mortality was approximately 50% in Costa
Rica, 75 to 85% in Panama, and 97% in the Galapagos Islands. However, they
subsequently found that the reefs in these locations returned to pre-El Niño
conditions in only a decade, and that bigger strides in reestablishment were
made in the warmer of the intervening years, demonstrating not only the fact
of reasonably rapid reef recovery, but also the adaptability of the
recovering corals to higher temperatures.

In the case of the more recent 1997-98 El Niño, which Normile (2000) credits
as causing "the most extensive coral bleaching event ever seen," a similar
remarkable reef recovery appears to be underway. Reefs in the Indian and
Pacific Oceans, in particular, he says, "seem to be recovering more quickly
than expected," and he quotes Terry Done of the Australian Institute of
Marine Science as saying that this rapid recovery "may indicate that reefs
are more resilient than we had thought." In fact, Normile reports that reefs
that "looked 'like a graveyard' after the 1998 bleaching" were found as
early as March of last year to contain "a surprising amount of new coral."

A similar observation was made by Mumby (1999) in reefs off Belize.
Immediately after corals there experienced what the scientist called "two of
the most severe disturbances of recent decades: massive coral bleaching and
Hurricane Mitch," which severely damaged 70 to 90% of adult coral colonies,
only 25% of new coral recruits exhibited signs of bleaching.  And only one
month after the damage was done, net bleaching-induced mortality of coral
recruits was essentially nonexistent. "Surprisingly," the author writes,
"coral bleaching alone had no measurable effect on either recruit density or
community structure."

In much the same fashion, giant kelp plants located near Bahia Tortugas,
Baja California, Mexico were essentially wiped out by the 1997-98 El Niño.
From the fall of 1997 to the spring of 1998, in fact, not a single kelp
could be found where extensive "forests" of these plants had grown
previously.  Less than a year later, however, in July of 1998, according to
Ladah et al. (1999), kelp plants were again observed to be growing in their
old haunts.  As to how this amazing recovery of the large alga might have
occurred, the authors suggest that "a microscopic stage that was not visible
during dive surveys survived the stressful conditions of ENSO and caused the
recruitment event, supporting the hypothesis that a bank of microscopic
forms can survive conditions stressful to macroscopic algae."  And in this
regard it is important to note that the symbionts of corals are also
microscopic algae, and that they too may be thus preserved during times of
intense thermal stress.

Another way by which corals may be able to survive prolonged periods of
solar and thermal stresses that can cause severe bleaching was described by
Salih et al. (2000) in the 14 December issue of Nature.  This most
interesting paper, of which Hoegh-Guldberg is a co-author, describes several
newly-discovered roles played by coral fluorescent pigments (FPs) in
protecting reefs from intense solar radiation and high temperatures.  These
pigments - whose "widespread abundance," according to the authors, "has not
been previously reported" - dissipate excess energy at wavelengths of low
photosynthetic activity when exposed to intense sunlight, as they also do by
reflecting visible and infrared light.  In addition, the scientists
determined that "FPs enhance the resistance to mass bleaching of corals
during periods of heat stress," thus ensuring "enhanced survival of a broad
range of corals" during episodes of anomalous warming, such as those that
typically accompany El Niño events.

In light of these important new discoveries about the abilities of corals
and their symbionts to both resist and recover from the effects of severe
solar and thermal stresses, and in consequence of the many real-world
observations of rapid reef recoveries from coral bleaching events associated
with the most massive El Niño of the past century, it is fair to say that
predictions of the demise of earth's coral reef ecosystems as a result of
possible future global warming must be considered dubious at best and
premature at the very least.  As knowledge continues to be acquired, it is
becoming ever more evident that corals exhibit a tenacity for survival that
is the complete antithesis of their legendary and oft-harped-upon fragility.

Dr. Craig D. Idso
Dr. Keith E. Idso

References

Glynn, P.W., Colley, S.B., Ting, J.H., Mate, J.L. and Guzman, H.M.  2000.
Reef coral reproduction in the eastern Pacific: Costa Rica, Panama and
Galapagos Islands (Ecuador). IV. Agariciidae, recruitment and recovery of
Pavona varians and Pavona sp.a.  Marine Biology 136: 785-805.

Hoegh-Guldberg, O.  1999.  Climate change, coral bleaching and the future of
the world's coral reefs.  Marine and Freshwater Research 50: 839-866.

Idso, S.B., Idso, C.D. and Idso, K.E.  2000.  CO2, global warming and coral
reefs: Prospects for the future.  Technology 7S: 71-93.

Ladah, L.B., Zertuche-Gonzalez, J.A. and Hernandez-Carmona, G.  1999.  Giant
kelp (Macrocystis pyrifera, Phaeophyceae) recruitment near its southern
limit in Baja California after mass disappearance during ENSO 1997-1998.
Journal of Phycology 35: 1106-1112.

Lough, J.M.  2000.  1997-98: Unprecedented thermal stress to coral reefs?
Geophysical Research Letters 27: 3901-3904.

Mumby, P.J.  1999.  Bleaching and hurricane disturbances to populations of
coral recruits in Belize.  Marine Ecology Progress Series 190: 27-35.

Normile, D.  2000.  Global Warming: Some coral bouncing back from El Niño.
Science 288: 941-942.

Salih, A., Larkum, A., Cox, G., Kuhl, M. and Hoegh-Guldberg, O.  2000.
Fluorescent pigments in corals are photoprotective.  Nature 408: 850-853.

Stone, L., Huppert, A., Rajagopalan, B., Bhasin, H. and Loya, Y.  1999.
Mass coral reef bleaching: A recent outcome of increased El Niño activity?
Ecology Letters 2: 325-330.
 
17 January 2001
Copyright © 2001.  Center for the Study of Carbon Dioxide and Global Change


============
(8) ICE AGES & INSTABLITIES

From Nature Science Update, 11 January 2001
http://www.nature.com/nature/fow/010111.html
 
The transition of our world from a temperate into a glacial state is one of
the most worrying potential impacts of climate change. It is imperative that
we understand exactly how stable our current climate is and what could
trigger another ice age.

A key factor in climate stability is the pattern of ocean circulation. The
network of global ocean currents, of which the Gulf Stream is a part,
transports not only water but also heat, with a profound effect on many
regions' climate. The Gulf Stream, for example, adds about 20% to the total
heat from the winter Sun in northern Europe, and its shut-down would bring
massive environmental upheaval.

In this week's Nature, two groups present robust climate simulations that
provide the first glimpses of the dynamics involved in ocean circulation.

Ganopolski and Rahmstorf examine ocean circulation under glacial conditions.
In particular, their study focuses on events known as 'Dansgaard-Oescheger
warmings', during which temperatures in Greenland can jump up to 10 °C in a
few decades. They suggest that the warmings correlate to shifts between two
metastable circulation patterns triggered by an excess of freshwater
entering the Nordic sea. This finding contrasts sharply with the generally
held belief that ocean circulation stops or is greatly reduced during ice
ages.

Hall and Stouffer use a finer-scale simulation to model future climate over
the next 15,000 years, starting with present-day conditions but excluding
further human impacts such as emissions of greenhouse gases. An unexpected
result is a dramatic cold spell in the North Atlantic region, lasting for
about 30-40 years, caused by an unusually long period of north-westerly
winds over Greenland.

Although neither of the chilly regimens predicted are likely to occur in the
foreseeable future, the studies are an important advance in our
understanding of the dynamics of both climate and ocean circulation.

----------------------------------------------------------------------------
----

Featured articles

Rapid changes of glacial climate simulated in a coupled climate model
ANDREY GANOPOLSKI, STEFAN RAHMSTORF
Nature 409, 153-158 (11 January 2001)

An abrupt climate event in a coupled ocean--atmosphere simulation without
external forcing
ALEX HALL, RONALD J. STOUFFER
Nature 409, 171-175 (11 January 2001)

Climatology: Glacial hiccups
DIDIER PAILLARD
The climate instability of glacial times probably resulted from abrupt
switches in ocean circulation. A computer-model simulation provides the
first glimpse of the dynamics involved.
Nature 409, 147-148 (11 January 2001)

climate: Great rivers of the ocean
Vast currents, like giant rivers, flow throughout the seas driven by
differences in temperature and salt concentration. These transport so much
heat around the globe that they play a critical role in shaping the Earth's
climate. (11 January 2001)

climate: Cold comfort for climate's future
New computer models hint that another cold snap could be round the corner.
(11 January 2001)

Related articles
Glacial circulation pattern

Changes in deep-water formation during the Younger Dryas event inferred from
10Be and 14C records
RAIMUND MUSCHELER, JÜRG BEER, GERHARD WAGNER, ROBERT C. FINKEL
Nature 408, 567-570 (30 November 2000)

Warming of the tropical Atlantic Ocean and slowdown of thermohaline
circulation during the last deglaciation
CARSTEN RÜHLEMANN, STEFAN MULITZA, PETER J. MÜLLER, GEROLD WEFER, RAINER
ZAHN
Nature 402, 511-514 (2 December 1999)

Rapid changes in the mechanism of ocean convection during the last glacial
period
TROND M. DOKKEN, EYSTEIN JANSEN
Nature 401, 458-461 (30 September 1999)

Rapid environmental changes in southern Europe during the last glacial
period
JUDY R. M. ALLEN, UTE BRANDT, ACHIM BRAUER, HANS-WOLFGANG HUBBERTEN, BRIAN
HUNTLEY, JÖRG KELLER, MICHAEL KRAML, ANDREAS MACKENSEN, JENS MINGRAM, JÖRG
F. W. NEGENDANK, NORBERT R. NOWACZYK, HEDI OBERHÄNSLI, WILLIAM A. WATTS,
SABINE WULF, BERND ZOLITSCHKA
Nature 400, 740-743 (19 August 1999)

Holocene periodicity in North Atlantic climate and deep-ocean flow south of
Iceland
GIANCARLO G. BIANCHI, I. NICHOLAS MCCAVE
Nature 397, 515-517 (11 February 1999)

Asynchrony of Antarctic and Greenland climate change during the last glacial
period
T. BLUNIER, J. CHAPPELLAZ, J. SCHWANDER, A. DÄLLENBACH, B. STAUFFER, T. F.
STOCKER, D. RAYNAUD, J. JOUZEL, H. B. CLAUSEN, C. U. HAMMER, S. J. JOHNSEN
Nature 394, 739-743 (20 August 1998)

Simulation of modern and glacial climates with a coupled global model of
intermediate complexity
ANDREY GANOPOLSKI, STEFAN RAHMSTORF, VLADIMIR PETOUKHOV, MARTIN CLAUSSEN
Nature 391, 351-356 (22 January 1998)

Palaeoclimatology: Icing the North Atlantic
RICHARD B. ALLEY
There is debate over the causes of the large and abrupt climate changes that
the North Atlantic region has experienced in the past (and may do in the
future). The driving forces of such changes might originate in the North
Atlantic itself, or could be transmitted to the region from elsewhere. New
evidence on the extent and movement of the British Ice Sheet around the end
of the last ice age supports the first contention, and in particular
implicates the advance and retreat of the Laurentide Ice Sheet in causing
some of the big climate jumps of the past.
Nature 392, 335-337 (26 March 1998)

Atmospheric CO2 concentration and millennial-scale climate change during the
last glacial period
B. STAUFFER, T. BLUNIER, A. DÄLLENBACH, A. INDERMÜHLE, J. SCHWANDER, T. F.
STOCKER, J. TSCHUMI, J. CHAPPELLAZ, D. RAYNAUD, C. U. HAMMER, H. B. CLAUSEN
Nature 392, 59-62 (5 March 1998)

Weaker Gulf Stream in the Florida Straits during the Last Glacial Maximum
JEAN LYNCH-STIEGLITZ, WILLIAM B. CURRY, NIALL SLOWEY
Nature 402, 644-648 (9 December 1999)
Temperate circulation pattern

Oceanography: Drifters reveal deep circulation
MONIKA RHEIN
Circulation in the North Atlantic at depths of 500-2,000 metres is largely
fed by water from the Labrador Sea. Data from an armada of subsurface floats
provide the first direct view of the flow of this water.
Nature 407, 30-31 (7 September 2000)

Mid-depth recirculation observed in the interior Labrador and Irminger seas
by direct velocity measurements
KARA L. LAVENDER, RUSS E. DAVIS, W. BRECHNER OWENS
Nature 407, 66-69 (7 September 2000)

Decadal variability in the outflow from the Nordic seas to the deep Atlantic
Ocean
SHELDON BACON
Nature 394, 871-874 (27 August 1998)
 
Nature © Macmillan Publishers Ltd 2001 Registered No. 785998 England. 

=============
(9) COLD COMFORT FOR CLIMATE'S FUTURE

From Nature Science Update, 12 January 2001
http://www.nature.com/nsu/010111/010111-5.html

HEIKE LANGENBERG
 
Plants, animals and humans all depend on a stable climate. Yet we tamper
with it, pumping large amounts of greenhouse gases into the atmosphere. Two
new computer models hint that even without man's interference, the climate
might suddenly turn cold.

Past climates can be reconstructed by drilling into the ice caps and the
ocean bed. This evidence reveals that the Earth's climate has changed
dramatically over the past 20,000 years. Temperatures over Greenland, for
example, have sometimes changed by as much as 10 °C in a few decades. The
key to the variability is ocean circulation, which moves vast quantities of
water - and therefore heat - around the globe.

Alex Hall, of Columbia University's Lamont-Doherty Earth Observatory in
Palisades, New York, and Ronald J. Stouffer of the US National Oceanic and
Atmospheric Administration's Geophysical Fluid Dynamics Laboratory in
Princeton, have simulated how the ocean's circulation would change over a
15,000-year period if the climate remained as it is today(1) - that is,
without any further human impacts.

One of the features of their model is a dramatic cold spell in the North
Atlantic region, lasting for about 30-40 years, caused by an unusually long
period of north-westerly winds over Greenland.

Ocean sediments record similar cold snaps, but these are thought to have
lasted longer and to have affected larger areas. "These differences could be
attributable to a model deficiency," the researchers admit. To simulate
15,000 years of climate, the duo had to exclude a lot of detail from their
model.

In the same issue of Nature(2), Andrey Ganopolski and Stefan Rahmstorf of
the Potsdam Institute for Climate Impact Research, Germany, describe their
computer simulation of the last ice age - which included rapid changes in
climate.

They find that the world's oceans may not have stopped circulating in
glacial times, as had been thought. Instead, the site in the North Atlantic
where cold, salty water sinks to the deep ocean probably shifted slightly
south.

This shift was brought about by reducing the amount of fresh water entering
the North Atlantic. Under these conditions, short warm periods give the
world a climate like today's for a few centuries. Longer cold spells occur
when more fresh water enters the North Atlantic and sends armadas of
icebergs off into the oceans.

Neither of these instabilities is likely to occur today, as the pattern of
ocean circulation is fundamentally different. For present-day conditions,
Ganopolski and Rahmstorf's model suggests that the current climate is more
stable.

But a large addition of fresh water into the North Atlantic could still
provoke change into a second scenario - a colder Earth where the oceans do
not circulate. The transition of our world from the first into the second
state is one of the most worrying potential impacts of climate change.

----------------------------------------------------------------------------
----
Hall, A. & Stouffer, R. J. An abrupt climate event in a coupled
ocean-atmosphere simulation without external forcing. Nature 409, 171-174
(2001).

Ganopolski, A. & Rahmstorf, S. Rapid changes of glacial climate simulated in
a coupled climate model. Nature 409, 153-158 (2001).

© Macmillan Magazines Ltd 2001 - NATURE NEWS SERVICE

====================
(10) COMPUTER SPECULATION ABOUT RAPID CLIMATE CHANGES DURING THE LAST ICE AGE
 
From Nature 409, 153 - 158 (2001) © Macmillan Publishers Ltd.
http://www.nature.com/cgi-taf/DynaPage.taf?file=/nature/journal/v409/n6817/abs/409153a0_fs.html  

Rapid changes of glacial climate simulated in a coupled climate model

ANDREY GANOPOLSKI AND STEFAN RAHMSTORF

Abrupt changes in climate, termed Dansgaard-Oeschger and Heinrich events,
have punctuated the last glacial period (100-10 kyr ago) but not the
Holocene (the past 10 kyr). Here we use an intermediate-complexity climate
model to investigate the stability of glacial climate, and we find that only
one mode of Atlantic Ocean circulation is stable: a cold mode with deep
water formation in the Atlantic Ocean south of Iceland. However, a 'warm'
circulation mode similar to the present-day Atlantic Ocean is only
marginally unstable, and temporary transitions to this warm mode can easily
be triggered. This leads to abrupt warm events in the model which share many
characteristics of the observed Dansgaard-Oeschger events. For a large
freshwater input (such as a large release of icebergs), the model's deep
water formation is temporarily switched off, causing no strong cooling in
Greenland but warming in Antarctica, as is observed for Heinrich events. Our
stability analysis provides an explanation why glacial climate is much more
variable than Holocene climate.

Nature © Macmillan Publishers Ltd 2001 Registered No. 785998 England.

=============
(11) WHAT TRIGGERS GLOBAL COOLING EVENTS?
 
From Nature 409, 171 - 175 (2001) © Macmillan Publishers Ltd.
http://www.nature.com/cgi-taf/DynaPage.taf?file=/nature/journal/v409/n6817/abs/409171a0_fs.html

An abrupt climate event in a coupled ocean-atmosphere simulation without
external forcing

ALEX HALL AND RONALD J. STOUFFER

Temperature reconstructions from the North Atlantic region indicate frequent
abrupt and severe climate fluctuations during the last glacial and Holocene
periods. The driving forces for these events are unclear and coupled
atmosphere-ocean models of global circulation have only simulated such
events by inserting large amounts of fresh water into the northern North
Atlantic Ocean. Here we report a drastic cooling event in a 15,000-yr
simulation of global circulation with present-day climate conditions without
the use of such external forcing. In our simulation, the annual average
surface temperature near southern Greenland spontaneously fell 6-10 standard
deviations below its mean value for a period of 30-40 yr. The event was
triggered by a persistent northwesterly wind that transported large amounts
of buoyant cold and fresh water into the northern North Atlantic Ocean.
Oceanic convection shut down in response to this flow, concentrating the
entire cooling of the northern North Atlantic by the colder atmosphere in
the uppermost ocean layer. Given the similarity between our simulation and
observed records of rapid cooling events, our results indicate that internal
atmospheric variability alone could have generated the extreme climate
disruptions in this region.

Nature © Macmillan Publishers Ltd 2001 Registered No. 785998 England.


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