CCNet, 55/2000 -  8 May 2000


     Asteroid 'Kleopatra' from Arecibo

     Its dogbone shape has made us laugh today
     and some of us may be suspicious - was the image
     'tweaked' a bit by someone with a sense of humour?
     The Iron Age has ended long ago, and 'rustbelt' industry
     on Earth is winding down, yet settlement in space
     might need strong structures, and lifting them from here
     would be extravagant.  Now there we see a place
     with ample iron and nickel for construction.
     One day we'll mine this metal bone, smelt iron on the spot
     if energy's available, and if not, ship it slow and cheaply
     to a place where space age smiths can fabricate
     the ploughshares needed for our New Worlds' farms
     or build great ships for our  new age of exploration.

     Malcolm Miller (c)               

    Jonathan Tate <>

    ASTRONOMY NOW, 8 May 2000


    Reiner M. Stoss <RSTOSS@HRZ1.HRZ.TU-Darmstadt.De>

    Michael Paine <>

    Alain Maury <>

    Andrew Yee <>


From Jonathan Tate <>


Welcome to the 10th edition of "Impact". When Impact 1 was published,
who would have believed that we would be where we are today by Issue
10! The government Task Force is forging ahead, having recently
returned from their fact-finding trip to the United States.

Reports from all sides of the discussions have been very positive, and
it appears that the Task Force is committed to producing a meaningful
and robust report to the minister in June. Apart from the Task Force,
other activities have included a busy lecture schedule that included a
presentation to the annual conference of the Institute of Emergency
Management in March. It was interesting to interact with those who plan
for and deal with natural disasters, and to find out what sort of
information, warning and advice that they require to deal with
catastrophic events. It would be true to say that the emergency services
are almost totally unaware of the nature and scale of the hazard from
cometary or asteroidal impacts, so events such as this are vital for
spreading the word.

The level of exposure in the media has been surprisingly high recently,
given that there has been no "Earth shattering" news. Astronomy Now
magazine published two related articles in their March edition in a
Focus section devoted to the impact hazard. Also in March there were two
television programmes, typically on the same evening, one dealing with
the search for a large iron meteorite in the Sahara desert, and the
other with the impact hazard in general. The latter, while being
generally  accurate, did give the impression that astronomers have the
NEO situation under control - a fact that is sadly erroneous.

Of course, all eyes are now on the progress of the NEAR spacecraft,
recently re-named "NEAR-Shoemaker" in honour of Gene Shoemaker, the
pioneer of impact studies, and inspiration for Spaceguard organisations
around the world. The stunning images of Eros are breathtaking, and
excellent science is already being done. Well done NASA, at least this
one worked!

The next issue of "Impact" will be due in July when I hope to be able
to brief you all on aspects of the Task Force report. Of course, there
is no reason why I should be party to this document, but I am hoping to
have at least some information by then. In the meantime, we will
continue to support the task Force in their work, reinforce our links
with Spaceguard organisations elsewhere, and "keep watching the skies".

Jay Tate
April 2000


The Task Force accepts the numerous threat assessments produced in the
  last decade; that the threat from asteroidal or cometary impacts,
  while being low probability but very high consequence, substantially
  exceeds the government's own threshold of risk tolerability.

At the policy and co-ordination level any Spaceguard programme must be
  international in nature.

Cost will preclude an immediate "Rolls-Royce" solution, but sensible
  investment will be commensurate with the hazard.


The requirement for some sort of national Spaceguard centre is
predicated on the following factors:

The international scientific community (represented by, amongst
  others, the UN and IAU) strongly supports the establishment of
  national Spaceguard Centres.

The detection of asteroids and comets is only the beginning of a long
  and complicated process to determine their orbits and their physical
  properties. The follow-up work required for this is not as glamorous
  as detection, but is just as essential. The UK has established
  expertise in the fields required for this work.

Without a national focus, the UK will be totally dependent on foreign
  agencies for its information. As we saw in March 1998 when it was
  announced that an asteroid (1997 XF11) had the potential to strike
  the Earth, there was no response from the British government at all.
  The public, looking for reassurance and information, was left in the
  lurch. Private and foreign organisations filled the gap and assumed
  responsibility for telling the public what was going on. There have
  been three more cases recently of asteroids with small but non-zero
  collision probabilities and again there has been no response from
  government departments. As the detection programmes in the US ramp
  up, cases like these will happen more and more frequently. A
  dedicated organisation is required to handle this situation.

NEO issues are complex, and require specialist handling/ specialist

The National Spaceguard Centre proposed by Spaceguard UK would be that
  focus, would undertake vital and complex research and could be
  established for 65,000, and run for 600,000 per year (i.e. it could
  operate for over fifty years for the price of one Tornado aircraft).


Do nothing - contrary to common sense and public opinion.

Establish a National Spaceguard Centre as proposed below - a modest
  but evolutionary approach.

Enter negotiations with European or other bodies - possibly the
  nightmare scenario (all talk, no action).

Recommend an accelerated programme, based on the three-phase proposal
  below - the "big bang" option.

Something else.


It is suggested, in line with the recommendations of the IAU and the UN,
that a National Spaceguard Centre be established, in three phases, with
the following Mission Statement:

To provide an expert domestic advisory service to the public,
  government, media and relevant authorities regarding the
  environmental hazard posed by natural extraterrestrial objects.

To facilitate UK involvement in the international Spaceguard

To conduct world-leading research regarding the nature and extent of
  this hazard.

Phase 1

Establish National Spaceguard Centre. The most cost-effective option is
to establish a central headquarters, with outstations optimally located
to achieve their missions. The following are proposed:

Armagh Observatory - The primary location, with the following

- Theoretical analysis of NEO astrometry, extrapolation of orbits,
  identification of priority follow-up
  observations, in collaboration with other UK and overseas

- Co-ordination of follow-up astrometry by other observers, both UK and

- Research into other effects of NEOs upon the terrestrial environment
  (atmospheric dusting, etc.).

- Modelling of atmospheric interactions by small (50-100 metre)

- Involvement in NEO space missions.

- Collaboration with NEO search programmes elsewhere.

- Investigations of feasible UK search programmes, e.g. using VISTA

- Investigations of the feasibility of a dedicated UK NEO search system.

- Investigations of outer solar system objects: theory and detection
  systems for bodies such as long-period
  comets, Halley-type comets (dark and active), Centaurs etc.

- Co-ordination of Public Understanding of Science and Technology (PUST)

Queen's University, Belfast - Lead centre for physical observations of

In or near Edinburgh (ROE, University of Edinburgh or  St Andrews) -
  To carry out the following responsibilities:

- Close collaboration with all aspects of the work at the main centre in

- Rapid access to the UKST plate library at ROE to make possible
  precoveries of NEOs discovered elsewhere.

- Lead centre for investigations of new NEO search programmes using
  VISTA data or other telescopic systems
  already in operation, and the design of novel NEO search systems.

- Collaborate with research staff at the Astronomy Technology Centre at

Near London - One public liaison / PUST manager employed to promote
  the activities of the National Spaceguard Centre and astronomy in
  general through media contacts, public presentations etc. as well as
  being a link with external bodies such as disaster management
  agencies, industry and others.

Total annual budget for the proposed national Spaceguard Centre -

Phase 2

Construction and operation of a 2m-class follow-up telescope (possibly
robotic), either as a national project or in collaboration with other
nations. Details and costings will be produced by the National
Spaceguard Centre.

Phase 3

Construction and operation of 4m-class detection telescope, either as a
national project or in collaboration with other nations. Details and
costings will be produced by the National Spaceguard Centre.


It is now clear that cosmic impacts have played an important role in
the geological and environmental development of the Earth, and may even
have been the dominant factor in the evolution of life. The universe in
which we live is a violent and unpredictable place, and this
realisation is driving a paradigm shift in scientific thinking
analogous with that caused by the work of Sir Isaac Newton and the
publication of Darwin's "On the Origin of Species by Means of Natural
Selection". The impact threat can be summarised as follows:

Rare. Major impacts are rare, therefore easy to dismiss as irrelevant
  to the current generation. Indeed, the whole subject has suffered
  from a substantial "giggle factor", though this is waning fast.

Devastating. Unlike other natural catastrophes there is no upper
  limit to the potential energy release into the ecosystem. Physical
  effects from the impact aside, even small impacts can have far
  reaching climatic effects and human institutions, which are far from
  robust in the face of disaster, are especially vulnerable in our
  global civilisation.

Avoidable. It is now technically possible to avoid or, at least
  mitigate the effects of impacts. Impacts have catastrophically
  disrupted the ecosphere in the past, and
  will again; the only question is when. But, for the first time in the
  history of our planet, there is a species with the ability to prevent
  cataclysm. We owe it to the future of mankind and all other forms of
  life that share our home to start the project that will prevent
  widespread destruction in the future.




On 8th April 2000, at the offices of KPMG in London, an extraordinary
meeting took place, bringing together many of the major amateur
organisations concerned with the development of space. The meeting was
organised by the Mars Society of UK.


The following were represented:
Space Age Associates
Space Settlers
Spaceguard UK
Mars Society
Discovery Space Club
British Rocketry Oral History Programme

The British Interplanetary Society and UKSEDS were also represented, but
only as observers, in line with their charitable status that precludes
them from active political lobbying.

Mission Statement

The delegates unanimously agreed a mission statement for the Space
development Council as follows:

"To provide mutual support and co-ordination between organisations
involved with the exploration and development of the space environment."

A constitution is under development, and a trawl for other organisations
that may wish to become involved is underway. Already there are a
number who have stated a desire to join the Council, boosting the
membership further.


Andrew Nimmo was elected Chairman of the council, and each organisation
represented has a member. A secretary, Captain John Broomfield, was
elected, and a treasurer will be elected soon.


Some readers might be tempted to criticise this initiative as another
example of amateur meddling in the realm of professionals, but it is
worth pointing out that the combined membership of the organisations
represented exceeds 4000. There are also a number of additional
organisations that are willing to join. Add this to the substantial
international membership of organisations such as the Planetary Society
and the various Spaceguard organisations around the world, and it
becomes obvious that the SDC will be a very significant lobby base for
UK participation in the development of space based activities.

The Future

The Space Development Council will now enter a phase of consolidation
and organisation before starting work on its primary task. The concept
of the SDC as a facilitator for co-operation and co-ordination is
simple, sensible and exciting. If all goes well this could become a
significant force in UK space development.

Spaceguard UK Perspective

At the beginning of the planning process for the SDC I raised some
concerns about Spaceguard UK's place in this organisation. In particular
I was concerned that Spaceguard UK, as a single-issue organisation,
would be out of place and uncomfortable lobbying for things like ISS and
trips to Mars. I pointed out to the group that we are not a "blue sky"
organisation, but that we have our feet firmly planted in reality, with
solid, costed proposals that have reached the highest levels of
government. In addition, we have the almost unanimous support of the
relevant experts in the scientific community and significant
international backing. However, the fact remains that we are, at
present, a lay group with an interest in the space environment. Having
debated the point with a number of people I decided that there is a
place for us on the SDC and have acted accordingly. As it happens,
Spaceguard is now one of the SDC priorities, so we have an added
resource to call upon should it become necessary!


From ASTRONOMY NOW, 8 May 2000

Dust grains older than comets
Comet Hale-Bopp. Photo: Courtesy NASA/JPL

Comets, the icy wanderers that occasionally grace the inner Solar
System, have long been considered the  oldest and most pristine
components of the primordial material out of which the planets and their
cortege of satellites were spawned. Now, new research has cast fresh
doubts on this long-cherished impression. In a paper published in the
April 27 edition of Nature, the American planetary scientist Scott
Messenger, at Washington University, has unearthed new and provocative
evidence suggesting that a class of interplanetary dust grains (IDPs)
might well have pre-dated the planetary system.

IDPs are a diverse assemblage of dusty material, with typical sizes
between 0.1 and 1.0 microns (a micron is one millionth of a metre), that
have retained much of their volatile inventory in the form of water ice
and other ices. And while this material continually rains down on the
earth, it is only in the upper atmosphere, particularly in the
stratosphere, that unaltered IDPs are routinely retrieved.

Messenger chemically analysed a variety of IDP specimens, including
isolated dust grains and cluster IDPs, comprising of many, loosely-bound
grains. After analysing 40 individual IDPs and 28 cluster IDPs,
Messenger showed that the latter were considerably more enriched in
deuterium - a 'heavy' species of atomic hydrogen, containing an extra
neutron in its atomic nucleus - relative to isolated individual IDPs.

Deuterium is a sensitive indicator of the physical environment in which
the grains formed. In particular, because its formation and
concentration inside dust grains is favoured in very cold environs,
deuterium tends to become enriched in the coldest parts of space,
particularly cool molecular clouds - the cocoons out of which new stars
emerge - where temperatures can be as low as 10 K.

But the biggest surprise came when Messenger compared the relative
abundance of deuterium in comets, primitive meteorites and cluster IDPs
studied to date. Though IDPs exhibited a larger overall range in
deuterium enrichments, they were often up to ten times more enriched in
deuterium relative to cometary material. Indeed, the enrichments are
consistent with the idea that cluster IDPs may have pre-dated the Solar
System and may even have been derived from a variety of cool molecular
clouds that brushed by this neck of the Galaxy before the Sun was even a
distant idea.

More work will undoubtedly serve to establish the precise age of these
tiny and ancient interstellar caravels. 

Copyright 2000, Astronomy Now



Donald Savage
Headquarters, Washington, DC                      May 4, 2000
(Phone: 202/358-1547)

Jane Platt
Jet Propulsion Laboratory, Pasadena, CA
(Phone: 818/354-0880)

RELEASE:  00-74


     NASA astronomers have collected the first-ever radar images
of a "main belt" asteroid, a metallic, dog bone-shaped rock the
size of New Jersey, an apparent leftover from an ancient, violent
cosmic collision.

     The asteroid, named 216 Kleopatra, is a large object in the
main asteroid belt between Mars and Jupiter; it measures about 135
miles (217 kilometers) long and about 58 miles (94 kilometers)
wide.  Kleopatra was discovered in 1880, but until now, its shape
was unknown.

     "With its dog bone shape, Kleopatra is one of the most
unusual asteroids we've seen in the Solar System," said Dr. Steven
Ostro of NASA's Jet Propulsion Laboratory, Pasadena, CA, who led a
team of astronomers observing Kleopatra with the 1,000-foot (305-
meter) telescope of the Arecibo Observatory in Puerto Rico. 
"Kleopatra could be the remnant of an incredibly violent collision
between two asteroids that did not completely shatter and disperse
all the fragments."

     The astronomers used the telescope to bounce radar signals
off Kleopatra.  With sophisticated computer-analysis techniques,
they decoded the echoes, transformed them into images, and
assembled a computer model of the asteroid's shape.  The Arecibo
telescope underwent major upgrades in the 1990s, which
dramatically improved its sensitivity and made it feasible to
image more distant objects. 

     These new radar images were obtained when Kleopatra was about
106 million miles (171 million kilometers) from Earth.  Travelling
at the speed of light, the transmitted signal took about 19
minutes to make the round trip to Kleopatra and back.

     "Getting images of Kleopatra from Arecibo was like using a
Los Angeles telescope the size of the human eye's lens to image a
car in New York," Ostro said.

     Kleopatra is one of several dozen asteroids whose coloring
suggests they contain metal.  Kleopatra's strong reflection of
radar signals indicates it is mostly metal, possibly a nickel-iron
alloy.  These objects were once heated, melted and differentiated
into structures containing a core, mantle and crust, much as the
Earth was formed.  Unlike Earth, those asteroids cooled and
solidified throughout, and many underwent massive collisions that
exposed their metallic cores.  In some cases, those collisions
launched fragments that eventually collided with Earth, becoming
iron meteorites like the one that created Meteor Crater in

     "But we don't need to worry about Kleopatra -- it will never
hit Earth," Ostro said.

      "The radar-based reconstruction of Kleopatra's shape shows
the object's two lobes connected by a handle, forming a shape that
resembles a distorted dumbbell, or dog bone," said Dr. R. Scott
Hudson of Washington State University, Pullman, WA.  "The shape
may have been produced by the collision of two objects that had
previously been thoroughly fractured and ground into piles of
loosely consolidated rubble.  Or, Kleopatra may once have been two
separate lobes in orbit around each other with empty space between
them, with subsequent impacts filling in the area between the
lobes with debris." 

     "The radar observations indicated the surface of Kleopatra is
porous and loosely consolidated, much like surface of the Moon,
although the composition is different," said Dr. Michael Nolan of
the Arecibo Observatory.   "Kleopatra's interior arrangement of
solid metal fragments and loose metallic rubble, and the geometry
of fractures within any solid components, are unknown. What is
clear is that this object's collision history is extremely

     "It is amazing that nature has produced a giant metallic
object with such a peculiar shape," said Ostro.  "We can think of
some possible scenarios, but at this point none is very
satisfying.  The object's existence is a perplexing mystery that
tells us how far we have to go to understand more about asteroid
shapes and collisions."

     The team's findings will appear in the May 5 issue of the
journal Science.  Ostro's team includes Hudson; Nolan and Jean-Luc
Margot of the Arecibo Observatory; Dr. Daniel Scheeres of the
University of Michigan, Ann Arbor; Dr. Donald Campbell of Cornell
University, Ithaca, N.Y; Dr. Christopher Magri of the University
of Maine at Farmington; and Jon Giorgini and Dr. Donald Yeomans of
the Jet Propulsion Laboratory.

     The Kleopatra images are available at:


The Arecibo Observatory is part of the National Astronomy and 
Ionosphere Center, operated by Cornell University for the National
Science Foundation.  The Kleopatra radar observations were supported by
NASA's Office of Space Science, Washington, DC. JPL is managed for NASA
by the California Institute of Technology in Pasadena.



From Reiner M. Stoss <RSTOSS@HRZ1.HRZ.TU-Darmstadt.De>

Duncan Steel wrote:

"Number of NEAs discovered from Siding Spring since the end of
1996 = ZERO"

This is not true. Rob McNaught/ M. Hartley discovered one in
1999 and one in 1997! Both have H brighter than 18.3mag and were
discovered at 413.

Not significant "but the story must be consistent
with reality" ;-)


Discovery date, site and discoverer(s)
1999 RM28     1999 09 03  413  R. H. McNaught
1997 WS22     1997 11 24  413  M. Hartley


Reiner Stoss
611 Starkenburg


From Michael Paine <>

Dear Benny,

Following the posting of my "Bigger telescopes" article on CCNet,
Jeremy Tatum from Spaceguard Canada sent me an email pointing out that
my list of major programs searching for NEOs left out the Canadian
program that uses the 1.85m Plaskett telescope on Vancouver Island.

See and

Jeremy advises that the program has "the largest telescope in the world
used in a regular programme of NEO follow-up astrometry... It is
recognized by those who observe (rather than write about) [point taken!]
asteroids that discovery and follow-up are more efficient when
performed independently by programmes dedicated to each of these ends. 
Discovery cannot proceed efficiently when encumbered by the need to do
follow-up astrometry, nor can follow-up be efficient if diverted by
discovery. Discovery and follow-up teams are typically in routine
e-mail contact with each other, so that discovery of potentially
interesting NEOs is immediately transmitted to follow-up teams."

He is quite correct in that my list is biased towards discovery rather
than follow-up work and I apologise for the oversight. I did stress
several times in the article (as did Don Yeomans) that follow-up work is
vital to Spaceguard.

I don't have the experience to respond in detail to Duncan Steel's
comments about the "Spaceguard Goal" - Duncan was involved with the
various discussions in the early 90s - but from the published reports I
thought the "goal" had started out as 80% of NEAs and increased to 90%.
Trouble is it is not clear whose goal it was!

Michael Paine


From Alain Maury <>

Over recent months, I have seen numerous critical remarks by various
persons concerning the Torino scale, aka the Binzel scale.

- My own personal point of view as an observer, who has had in the past
to answer questions from journalists, is that I will never use Binzel's
scale. A scale is something that measures something. The something we
are referring to in this case is a probability of something happening
(or better: not happening) in the future.

Moreover, this something is going to fluctuate a lot, depending on
observations in the past or in the future. Most likely, we will have to
worry about more objects similar to the five that are currently in the
NEODys page. Alan Harris of JPL, in a personal communication,
pointed out quite correctly that it may take a million objects with an
impact probability of one millionth before we get one worth worrying
about, i.e., and not surprisingly so, it is very unlikely that in our
lifetimes we shall have anything other than objects having a given
impact probability after the first observations, but which, with a new
set of observations, shall turn into level 0 objects (I mean, white on
the Binzel scale: harmless).

To be logical, the Scale would have to relate to the probability of a
large explosion happening on the surface of the Earth caused by the
impact of an asteroid. My guess is that the public is not interested in
"probability" of large explosions occurring. What  it wants to know is
whether or not *this* object will hit the earth: yes or no, when and do
we have time to do something about it.

While with insufficient astrometric observations the orbital elements
are quite uncertain, leading to uncertain probabilities, even lousier
photometric observations mean uncertain taxonomic determinations that do
not allow more than a rough measure of the mass of the object and
estimates of the consequences of the impact. I mean, I would not claim
such an object is harmless or not when I know perfectly well that I have
no way of establishing its diameter and composition, other than from a
rough single-color photometric observation. With the current Binzel
scale, every person concerned knows that a metallic "yellow  4" is a
stony "orange 7".

- A scale is something that is adopted and used by most specialists in
the field. In this respect, I feel quite frustrated by the way things
were handled in Torino. Subcommittees reflected on various aspects of
the NEO problem. One subcommittee (composed, I assume, of people having
some expertise) discussed the scale. The meeting ended before clear
conclusions could be drawn, and we were told that small committees
would draw up recommendations for us. Since I was neither in the
subgroup that discussed this scale, nor in the small committee that
finished the work, I have to say that, despite all that has been said,
here and there about this scale, and despite its endorsement by the IAU,
I have yet to hear a convincing argument in favor of it, other than

- As far as I am concerned, I will use the Maury scale (MS for short:-),
which is a simple binary scale (i.e. perfectly harmless and we say so,
or not harmless at first sight and we take the time to explain what we
know and what we don't), not approved by the IAU.
Most, if not all of the time, the first level of the MS is used, and it
is a simple phrase that, I guess, will be more than enough to answer the
questions of most journalists:

  "We have here an object, discovered a few weeks/months ago (name  
  the discoverer and the country in which the discovery was made),
  whose orbit was computed by several scientists working in this field 
  (state names and institutions/countries), which shows a possible  
  close approach to the Earth in (give the date) with a probability of 
  impact of (give the probability). This means that there is a  
  probability of (give one minus impact probability, usually a number  
  like 99.9999%) that there will be no impact at that time. Close  
  approaches of asteroids to the Earth, astronomically speaking, are  
  not such rare events, but it is difficult, many years in advance, to 
  make very precise estimations of impacts. So far, all objects for  
  which such non-zero impact probabilities were computed, and for which
  new observations became available, were shown to be completely  
  harmless. We know very little about this object, which is probably  
  between (give a size estimate) and more observations are needed".

I think journalists and the public will get this idea pretty well, as
they have in the past, at least much better than an obscure scale,
putting numbers, colors and subclasses where none is needed.

This is much longer than to say "this object is a yellow 3" and then
leave. But it is much shorter than to say the same, then have to explain
it, trying --if possible-- during the conversation to explain what the
above phrase says so concisely.

In the very extremely unlikely case that the first level MS would not be
adequate (if we were unlucky enough to find an object really worth
worrying about), I will have to improvise a second one that will
describe the situation as exactly as possible. We should say what we
know and what we don't, at the moment of the interview, explaining why
the situation might still change, in the most precise and honest manner
possible. If such a case should occur, I think we will have much more
time to talk to the press, and more time and ways to make fools of
ourselves, unless of course the object is a "red 8" coming in a few
hours, and the interview is held just at the wrong place at the wrong
time, in which case, I recommend leaving the studio as soon as possible.

Alain Maury

MODERATOR'S NOTE: I should point out that, almost one year after the
Torino IMPACT meeting, none of the recommendations made by the
delegates have been made available yet. I understand that there are
ongoing attempts to change or overturn some of the decisions taken in
Turin. Unless the IAU can clean up the Torino mess soon, these
shenanigans and delays do not bode well for the forthcoming IAU General
Assembly in Manchester.


From Andrew Yee < >

New Scientist

Contact: Claire Bowles, 0171 331 2751,

Don't blame the Sun

GREENHOUSE effect sceptics may have lost their final excuse. The Sun
has been dethroned as the dominant source of climate change, leaving
the finger of blame pointing at humans.

A correlation between the sunspot cycle and temperatures in the
northern hemisphere seemed to account for most of the warming seen up
until 1985. But new results reveal that for the past 15 years something
other than the Sun -- probably greenhouse emissions -- has pushed
temperatures higher.

In 1991, Knud Lassen of the Danish Meteorological Institute in
Copenhagen and his colleague Eigil Friis-Christensen found a strong
correlation between the length of the solar cycle and temperature
changes throughout the northern hemisphere. Initially, they used
sunspot and temperature measurements from 1861 to 1989, but later found
that climate records dating back four centuries supported their
findings. The mysterious -- and unexplained -- relationship appeared to
account for nearly 80 per cent of the measured temperature changes over
this period.       

Now Lassen and astrophysicist Peter Thejll have updated the research
and found that while the solar cycle still accounts for about half the
temperature rise since 1900, it fails to explain a rise of 0.4 C since
1980. "The curves diverge after 1980," says Thejll, "and it's a
startlingly large deviation. Something else is acting on the climate." 

Although they can't be sure, they suspect that emissions from the
burning of fossil fuels are responsible. "It has the fingerprints of
the greenhouse effect," says Thejll. Other climatologists agree. "It
sounds like an actual piece of evidence for greenhouse warming," says
Richard Betts of Britain's Hadley Centre for Climate Prediction and
Research in Bracknell, Berkshire. "Any natural effect would swamp the
small early changes, so you'd expect to see the larger changes more

Others, however, remain sceptical about this line of research. Tom
Wigley at the National Center for Atmospheric Research in Boulder,
Colorado, who in 1992 criticised Lassen's initial research, points out
that since then no one has provided a convincing physical explanation
for the correlation between the sunspot cycle and temperature. Wigley
accepts that solar effects may have dominated until about 1950, but
certainly not as late as 1980.       

Lassen and Thejll recognise that the link between the solar cycle and
climate is controversial. But they hope their new findings will move
climate-change researchers towards a more balanced view. "It became
political," says Thejll. "We're now seeing that the Sun plays a role,
and something in addition to the Sun. Maybe that will help people see
there is room for both."

New Scientist issue: 6th MAY 2000


[NOTE: An illustration supporting this release is available at ]

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