|
|
|
|
News & Views item - February 2010 |
Australian Science Media Centre Produces Q&A on Climate Change. (February 25, 2010)
Australian Science Media Centre – 25
February 2010
RAPID ROUNDUP:
Climate confusion - Scientists answer your questions
After conversations and emails from a number of media
representatives, AusSMC decided to put the most pressing questions about
climate change to a panel of climate scientists.
Here are questions they received with links to the answers from climate scientists.
Further answers will be added to the AusSMC website as they come to hand:
_________________
Professor Steven Sherwood, Climate Change
Research Centre at the University of New South Wales
“The trend on meaningful time-scales has remained upward.
Recent observations remain consistent with mainstream models and theories
that predict warming. A longer period of sustained flat or cooling
temperatures would be needed to challenge them.”
Associate Professor Kevin Walsh, Associate
Professor of meteorology in the School of Earth Sciences at the University
of Melbourne
“It is getting warmer, but not at the same rate
everywhere. Take the global average temperature, for instance. The year 1998
was the warmest year to date (because it was a big El Nino year), and if a
trend line is calculated starting at 1998 going to 2009, this trend is not
statistically significant. But if you take the same trend from 1997 or 1999,
the upward temperature trend is statistically significant. And if you take a
trend from 1900 to 2009, the upward temperature trend is REALLY
statistically significant.
Why do I pick 1998? Because it is often said that the lack
of a trend since 1998 invalidates the global warming hypothesis. But global
warming is a trend superimposed upon natural variability, variability that
still exists despite global warming. This means every so often you would
expect a spike in the global average arising from natural variability alone,
just like the year 1998. It would be MUCH more surprising if the global
average temperature just kept on going up, year after year, without some
years of slightly cooler temperatures.”
Professor Neville Nicholls, Professorial
Fellow in the School of Geography and Environmental Science at Monash
University
“The graph below shows global temperatures of the lower
atmosphere (just above the Earth’s surface) averaged over November-January
each year (ending in November 2009 – January 2010). The data are from Dr Roy
Spencer and Dr John Christy (http://vortex.nsstc.uah.edu/data/msu/t2lt/uahncdc.lt),
whose data have been used in the past to suggest that warming has ‘stopped’.
As the figure shows, global warming is going strong, despite rumours of its
demise. Global temperatures have increased about 0.5C since 1979/80
(satellite data started in 1979). Other data (temperatures over land, sea
surface temperatures) show similar warming.”
Dr Paul Beggs, Senior Lecturer in
the Division of Environmental and Life Sciences at Macquarie University, NSW
“The message from climate change experts about warming in
recent years has been clear and consistent. Warming of the climate
system is unequivocal. It is getting warmer.”
Professor
Steven Sherwood,
Climate Change Research Centre at the University of New South Wales
“Most
studies find that the warming stands out statistically, though this will be
contested. What is more important is that the warming was predicted
decades ago based on physical principles, and the predictions came true.
The predicted future warming is much larger, if emissions continue. We
ain't seen nothing yet.”
Professor Steven Sherwood, Climate Change
Research Centre at the University of New South Wales
“Yes, satellites can measure the greenhouse effect and its
increase over time. These claims are false.”
Associate Professor Kevin Walsh, Associate
Professor of meteorology in the School of Earth Sciences at the University
of Melbourne
“If there is no link between increased concentrations of
carbon dioxide in the atmosphere and global warming, then we don’t
understand physics that has been used successfully in other scientific
fields since the nineteenth century. There has to be a link. The controversy
is about the size of the effect, not whether it exists or not.”
Professor Neville Nicholls, Professorial Fellow
in the School of Geography and Environmental Science at Monash University,
Melbourne
“Confidence in the reality of the link between carbon
dioxide in the atmosphere and warming comes from three sources:
1.
Laboratory experiments 150 years ago (and repeated many times since –
you can even see a demonstration on YouTube) show that carbon dioxide is a
greenhouse gas and that increasing its concentration will lead to warming
unless other processes (a weakening sun, or massive volcanoes, or dust from
an asteroid hitting the earth) offset this warming.
2.
Predictions of the amount of warming expected from the likely
increases in carbon dioxide have been made since at least 1959 (the 1959
prediction was published in Scientific American at the time). These
predictions were initially done without the use of climate models, and were
just based on physics. By the early 1970s, warming (up to the end of the 20th
century) was being accurately predicted in journals such as Nature,
using the climate models available at that time. Better models were
used in 1988 to make predictions of warming, again proving quite accurate.
Successful prediction is the standard technique that scientists use to
confirm their understanding of a process. The success of repeated
predictions (made over 50 years) of warming confirm our understanding of the
physics of the greenhouse effect.
3.
In recent decades, a large number of more sophisticated climate
models that take account of a wider range of climate mechanisms, and do a
better job of simulating atmospheric behaviour, have been shown to reproduce
the observed 20th century warming and cooling episodes when they
use anthropogenic influences (including greenhouse gas increases) but cannot
reproduce the observed temperature behaviour if only natural processes
(solar variations and volcanoes) are included in the model. Some of the
variations in the Earth’s climate in previous ages were caused by changes in
the amount of energy received from the Sun. But satellite observations show
that there has not been a trend to more heating from the Sun over recent
decades, so the Sun has not caused the warming of the past 50 years.”
Dr Paul Beggs, Senior Lecturer in
the Division of Environmental and Life Sciences at Macquarie University, NSW
“The sceptics are wrong. There is considerable
evidence of a link between the observed increase in anthropogenic greenhouse
gas concentrations in the atmosphere and the observed increase in global
average temperatures. The link is clear.”
Professor
Steven Sherwood,
Climate Change Research Centre at the University of New South Wales
“This event
has been horribly overblown. The unfounded claims that have caused the
controversy were so minor, they were not even mentioned in the report's
Executive Summary. The executive summaries are vetted very very
thoroughly, could not have errors of this kind, and contain all the findings
of importance to policymakers. The bowels of the text, where errors
have been found, are not vetted very well (especially in the WG II and III
reports) and IPCC needs to address this.
It is worth
pointing out that the sin of the IPCC--publishing a prediction with no
scientific foundation--is one that contrarians do every time they say we
have nothing to worry about.”
Associate
Professor Kevin Walsh,
Associate
Professor of Meteorology in the School of Earth Sciences at the University
of Melbourne
“I’m assuming that most will understand the process of
peer review, but maybe not, so I’ll just briefly describe it. A “peer” is
someone who is an expert in the field of the work being evaluated, or who is
an expert in a closely related scientific field. Often, they will be
scientific competitors of the scientists whose work is being evaluated.
Sometimes, the reviewer may be deeply sceptical about the topic of the work
being assessed. So peer review is certainly not a self-congratulation
society of like-minded scientists. On the other hand, though, even rigorous
peer review can let things slip through, or assess work incompletely. It’s
not surprising, therefore, that in the several thousand pages of the IPCC
reports, a few problems have been found with the review process.
Can peer review be trusted? I guess the next question is
what is the alternative? Review by non-peers, or in other words by
non-experts? This does not seem like a viable alternative. There will always
be some issues with any review process. But peer review is the best process
that we have come up with so far to perform quality control on scientific
publications.”
Professor
Neville Nicholls, Professorial Fellow in the School
of Geography and Environmental Science at Monash University, Melbourne
“In 2009 there were 7,541 peer-reviewed
scientific papers published in the peer-reviewed literature with the topic
of ‘global warming’ or ‘greenhouse effect’ or ‘climate change’. With such a
large number of papers there must be some that are incorrect. But the large
number indicates that this is a very busy field, and such a busy field
should ensure that most of the work published is checked by many other
scientists.
All those journal papers have been
reviewed by 2-3 other scientists, prior to their publication. The IPCC then
assesses this mountain of published scientific literature. The Fourth
Assessment cites over 10,000 papers from the scientific literature, most of
which have already been through the peer-review process to get into the
scientific literature. The IPCC reports themselves are subjected to four
reviews, over a 2-3 year period. The IPCC Fourth Assessment received about
90,000 comments from about 2,500 reviewers. The review comments are publicly
available, as are the responses of the authors. So, any errors made by the
authors in response to the reviewer comments should be found pretty quickly.
It is hard to conceive of a more comprehensive and transparent process than
that used by the IPCC.
Once the IPCC reports themselves are
completed, there is another process of review to prepare and revise
summaries of the reports. Every sentence in these summaries is discussed and
argued about (and finally agreed by consensus – not a vote) by scientists
and representatives from more than 130 governments (and many of these
government representatives are also scientists). It is hard to imagine
any process of assessing a complex subject that would be subject to more
comprehensive debate and review.”
Dr
Paul Beggs,
Senior Lecturer in the
Division of Environmental and Life Sciences at Macquarie University, NSW
“Peer
review can certainly be trusted, particularly the IPCC peer review process
which is arguably the most rigorous and transparent peer review process in
the history of science. Similarly, of course we can trust the science
and scientists. Asking if we can trust the science and the scientists
is like asking if we can trust medicine and the doctors. Just like we
consult a doctor when we are unwell, we must trust and accept the consensus
of the world's climate change experts as clearly presented in the IPCC's
most recent Assessment Report (published in 2007, the year it was jointly
awarded the Nobel Peace Prize with Al Gore).”
Professor
Steven Sherwood,
Climate Change Research Centre at the University of New South Wales
“If I
began pumping carbon monoxide into your office, and an alarm soon went off
indicating CO levels were rising toward dangerous levels, would you dismiss
concerns on the basis that there is much more CO in the global atmosphere
than in your office and that you don't fully understand the building's air
handling system?
This is a
slight of hand to distract the public from the clear facts that carbon
dioxide rises are unequivocally due to fossil fuel burning (plus a few
smaller sources). It sounds inspired by Ian Plimer's book. His
arguments rest on false assertions (which he continues to refuse to recant)
and a willingness to ignore the most crucial evidence and arguments.
His assertion that we don't know why CO2 levels are rising or that is
natural is preposterous and easily disproved.”
Professor Steven Sherwood, Climate Change
Research Centre at the University of New South Wales
“The sceptics here are (for once) technically correct, in
that there is no proven link--yet-- between Murray-Darling drought and
climate change. BUT...(a) there are good reasons to expect most of
Australia to gradually dry due to warming, regardless of any particular
drought happening right now; (b) the severe droughts in southern Victoria
and southwest Australia have been more firmly attributed to global warming;
and (c) temperatures everywhere, including the Murray-Darling, are rising
which increases the need for rainfall. Thus drought is worsening even
though rain isn't decreasing (because it isn't increasing enough).”
Professor Neville Nicholls, Professorial Fellow
in the School of Geography and Environmental Science at Monash University,
Melbourne
“Annual MDB rainfall in each of the last nine years has
been below 500mm (you can find these data at the Bureau of Meteorology’s web
page). Prior to this dry period, the longest run of years below 500mm, since
we have had decent data (starting in 1900), was six years (1925-1930). So,
the current dry period is 50% longer than the previous record dry period.
But this current dry period might still be just a fluke, or natural
variability. We cannot confidently attribute it to global warming.”
Professor Steven Sherwood, Climate Change
Research Centre at the University of New South Wales
“For some extremes this is true, but there is little doubt
that a warmer climate will bring more extreme heat waves, and heavier
downpours in areas that still receive ample rain. These things are
being observed. We also expect more frequent and severe droughts,
which is also being observed.”
Associate Professor Kevin Walsh,
Associate Professor of meteorology in the School of Earth Sciences at the
University of Melbourne
“The link is weak, but not necessarily unproven. I
say it is weak because, so far, there is little indication of detectable
trends in extreme weather events that can be tied directly to the warming
that has occurred to date. One exception, of course, is increases in extreme
high temperatures, which have been demonstrated in some regions of the globe
to be associated with climate change trends. But for other phenomena such as
tropical cyclones, trends have not been unambiguously associated with global
warming. On the other hand, climate predictions suggest that we should start
to see trends in some of these other phenomena, but probably not until later
this century.”
Professor Neville Nicholls, Professorial Fellow
in the School of Geography and Environmental Science at Monash University,
Melbourne
“Hot extremes (hot days and nights, and heat waves) over
much of the world have increased as the world has warmed over the past 50
years, while cold events (cold days, cold nights) have decreased in
frequency and intensity. The link between these changes in extremes and
global warming is very clear. Linking global warming and other types of
extremes is more complicated. Some extremes (tornadoes, strong winds) are
not monitored well enough to determine if they are changing. Some (tropical
cyclones) are not modeled sufficiently well to make confident predictions of
changes, or to understand the causes of changes. Some extremes (droughts,
heavy rains) have been changing in different ways in different regions, so
it is hard to make a global assessment. All the above issues are discussed
in the IPCC Fourth Assessment reports.”
Professor
Steven Sherwood,
Climate Change Research Centre at the University of New South Wales
“Relatively
few things are certain, but these things should compel people to action.
They are: (a) human activities (mainly fossil fuel burning) are increasing
greenhouse gas levels, (b) increased greenhouse gas levels have a warming
effect, and (c) we are observing warming at the rate calculated from this
effect. None of this is contestable.”
Associate
Professor Kevin Walsh,
Associate
Professor of meteorology in the School of Earth Sciences at the University
of Melbourne
“If we wait until we have absolute certainty on all
aspects of this topic before acting, we will never act. People in their
daily and professional lives make decisions all the time without being
absolutely certain about the consequences. Regarding uncertainty: most
scientists – and not just most climate scientists, most scientists in
general – are pretty certain that the observed global warming over the past
100 years is due to man-made greenhouse gases, and have been for some time.
But it seems very difficult to get this message across to the public. One
reason is that it is much harder to figure out what the effect of global
warming will be at the local level, for example, what will be the average
rainfall in the Murray-Darling basin in 2050. It’s harder because
calculations involving rainfall are harder to do, since some of the
processes involved are not as well understood as they should be, and so the
uncertainty is greater. We are dealing here with likelihood and risk
management, not certainty. The important thing for scientists (and
journalists) is to clearly convey an appreciation of the likelihood of a
particular prediction, which will range from almost certain (e.g. that the
global temperature will continue to increase, although not always every
year) to predictions of much lower certainty. But some predictions ARE
certain enough for action to be taken, and it has – like restrictions on the
building of new structures close to the coast due to predicted sea level
rise, for instance. The only way to reduce uncertainty is with better
science.”
Dr
Paul Beggs,
Senior Lecturer in the
Division of Environmental and Life Sciences at Macquarie University
“There is,
of course, some uncertainty regarding some aspects of climate change, but we
can be sure about many things. I think the public is being
underestimated if the media or anyone else thinks it will only act if it has
certainty on this issue. The public acts without certainly all the
time. Many people are already acting on climate change. While
the research on climate change must continue, I look forward to much more
community discussion of the many responses to climate change.”
Professor
Steven Sherwood,
Climate
Change Research Centre at the University of New South Wales
“Monckton
has no credibility on this issue and is peddling snake oil. It is true that
meaningful reduction will not be easy, but economic studies show that half
the job can be accomplished at zero net cost. It just requires
changing habits and standing up to some special interest groups.”
Professor Steven Sherwood, Climate Change
Research Centre at the University of New South Wales
“That would count as weather, not climate. The real
question in science is whether observations are consistent with different
hypotheses. The snowstorms in Europe and the US, for example, are
fully consistent with greenhouse warming predictions: less than one degree
of warming will not put an end to snowstorms! The only evidence that
matters is that which would be inconsistent with one argument or the other.
The observed global warming, and its geographic pattern, is inconsistent
with the notion that greenhouse gases have no effect on climate and has been
shown so in many independent, peer-reviewed studies.”
Professor Neville Nicholls, Professorial Fellow
in the School of Geography and Environmental Science at Monash University,
Melbourne
“As the IPCC Fourth Assessment says very clearly, a single
extreme event cannot be attributed to global warming (or any other cause).
This is the case whether we are talking about a single storm or a single hot
summer. But a consistent string of extreme events of the same type - such as
the run of unprecedented heat waves that have hit Australia in the past few
years - starts to look a lot more like climate change, and less like a
fluke.”
Professor Steven Sherwood, Climate Change
Research Centre at the University of New South Wales
“We can predict temperature rises over the long term to
about a factor of 2, which isn't great and means we are dealing here with
probabilities. To have a decent chance of avoiding an eventual 2C rise
would require that future emissions be roughly equal to all past emissions.
This would require emissions to peak in the next decade or so and then
decline almost as fast as they rose over the 20th century.”
-----------
Australian Science Media
Centre (AusSMC)
Street address: The Science
Exchange, 55 Exchange Place, ADELAIDE SA 5000
Postal address: PO Box
237, RUNDLE MALL SA 5000
Ph: (08) 7120 8666 |
Fax: (08) 8231 7333 |
info@aussmc.org
|
www.aussmc.org
The
Australian Science Media Centre (AusSMC) is an independent, non-profit
service for the news media, giving journalists direct access to
evidence-based science and expertise. The national centre is advised by a
Science Advisory Panel and governed by a Board of Management. It is
supported by a wide variety of sectors with each contribution capped at 10%
of total running costs. Foundation sponsors are the ABC, APN News &
Media, Cochlear Foundation Ltd, CSIRO, the Govt of SA, Innovative Research
Universities Australia, Macquarie Bank, Media Monitors, News Ltd, New South
Wales Govt, Orica Ltd, Queensland Govt, ResMed Inc, the Royal Institution of
Australia, the State Govt of Victoria, Network Ten and the University of
Melbourne. Gold Sponsors are ATSE, Cisco Systems Inc., CSL Ltd, IBM
Australia, Johnson Winter & Slattery, Shell Australia Ltd and the University
of Adelaide. Supporters include AMTA, FASTS, Microsoft, Powerhouse Museum
and Flinders University.
Disclaimer:
Please note that any views expressed are the personal opinions of the
experts named. They do not represent the views of the AusSMC or any
other organisation unless specifically stated. The AusSMC attempts to
provide a range of views from the scientific community.