In a recent blog entry, I discussed why professional societies should issue position papers on issues of public importance. That was the topic of an exchange of letters to Physics Today, including mine. Now, as if to emphasize my reasoning, the UK Royal Society has published an excellent and informative 16-page summary of the scientific issues surrounding climate change for general readers.
That report begins with a section of background on climate and climate science. It then has a section describing “Aspects of climate change on which there is wide agreement.” Following that is “Aspects of climate change where there is a wide consensus but continuing debate and discussion. Next comes “Aspects that are not well understood,” followed by developments in climate science, concluding remarks, background reading, and acknowledgments.
As a scientist, I am most pleased that the report enables non-scientists an opportunity to see how scientists draw conclusions based on evidence, consider dissenting interpretations, and develop a consensus view with clearly stated strengths and limitations.
You can download the pamphlet by following this link. I highly recommend that you read the report and not be content with summaries, including this one.
However, knowing that many of you want just a summary of that summary report, here are the section headings. I also include some excerpts:
Climate and climate change: some background science
The greenhouse effect
Climate change
Mechanisms of global climate change
Modelling the climate system
Changes in global-average surface temperature
Other changes in climate
Aspects of climate change on which there is wide agreement
Changes in atmospheric composition
Climate forcing by greenhouse gas changes
Carbon dioxide and climate
Aspects of climate change where there is a wide consensus but continuing debate and discussion
The carbon cycle and climate
Other drivers of global climate change
[NOTE: These include:
* Volcanic eruptions
* Natural forcing due to sustained variations in the energy emitted by the Sun
* Human activity]
Climate sensitivity
Attribution of climate change
Excerpt:
The size and sustained nature of the observed global-average surface warming on
decadal and longer timescales greatly exceeds the internal climate variability simulated
by the complex climate models. Unless this variability has been grossly underestimated,
the observed climate change must result from natural and/or human-induced climate
forcing.
When only natural climate forcings are put into climate models, the models are
incapable of reproducing the size of the observed increase in global-average surface
temperatures over the past 50 years. However, when the models include estimates of
forcings resulting from human activity, they can reproduce the increase. The same
result is found, albeit with a greater spread between different models, for the simulation
of observed surface temperature changes for each of the habitable continents
separately.
When known uncertainties in both observed trends and climate models are taken into
account, the observed vertical and latitudinal variations of temperature change are also
broadly consistent with those expected from a dominant role for human activity. There
is an ongoing controversy concerning whether or not the increased warming with
height in the tropical regions given by climate models is supported by satellite
measurements.
Future climate change
Excerpt:
As with almost any attempts to forecast future conditions, projections of future climate
change depend on a number of factors. Future emissions due to human activity will
depend on social, technological and population changes which cannot be known with
confidence. The underlying uncertainties in climate science and the inability to predict
precisely the size of future natural climate forcing mechanisms mean that projections
must be made which take into account the range of uncertainties across these different
areas.
-snip-
Aspects that are not well understood
Excerpt:
There is currently insufficient understanding of the enhanced melting and retreat of the
ice sheets on Greenland and West Antarctica to predict exactly how much the rate of
sea level rise will increase above that observed in the past century (see paragraph 45)
for a given temperature increase. Similarly, the possibility of large changes in the
circulation of the North Atlantic Ocean cannot be assessed with confidence. The latter
limits the ability to predict with confidence what changes in climate will occur in
Western Europe….
[NOTE: I consider this to be the most significant uncertainty, and I reviewed a book that speculates what might happen if the melting is much greater than projected.]
Developments in climate science
Excerpt:
Climate change science has advanced markedly over the past 20 years, as a result of
many factors. These include improved methods for handling long-term climate data
sets, the ever-lengthening record of climate observations, improved measurement
techniques, including those from satellites, better understanding of the climate system,
improved methods for simulating the climate system, and increased computer power.
One indication of these advances is the increasing degree of confidence in the
attribution of climate change to human activity, as expressed in the key conclusions of
IPCC Working Group 1 (WG1) in its assessments.
-snip-
Remaining uncertainties are the subject of ongoing research worldwide….
There remains the possibility that hitherto unknown aspects of the climate and climate
change could emerge and lead to significant modifications in our understanding.
Concluding remarks [Note: This section is reproduced in full]
There is strong evidence that changes in greenhouse gas concentrations due to human
activity are the dominant cause of the global warming that has taken place over the last
half century. This warming trend is expected to continue as are changes in precipitation
over the long term in many regions. Further and more rapid increases in sea level are
likely which will have profound implications for coastal communities and ecosystems.
It is not possible to determine exactly how much the Earth will warm or exactly how the
climate will change in the future, but careful estimates of potential changes and
associated uncertainties have been made. Scientists continue to work to narrow these
areas of uncertainty. Uncertainty can work both ways, since the changes and their
impacts may be either smaller or larger than those projected.
Like many important decisions, policy choices about climate change have to be made in
the absence of perfect knowledge. Even if the remaining uncertainties were
substantially resolved, the wide variety of interests, cultures and beliefs in society would
make consensus about such choices difficult to achieve. However, the potential impacts
of climate change are sufficiently serious that important decisions will need to be made.
Climate science – including the substantial body of knowledge that is already well
established, and the results of future research – is the essential basis for future climate
projections and planning, and must be a vital component of public reasoning in this
complex and challenging area.
Background Reading
Acknowledgments
An addendum: For those who would like to see how I have handled this topic in my writing for young readers, see my webpage about my book Seven Wonders of Exploration Technology (Twenty-First Century Books, 2010).
Dear Dr. Bortz,
Thank you for this very well designed site. I am pleased that a scientist of your stature is willing to host an open discussion on the causes of global climate change.
I am not a climatologist, but I was critical of the IPCC reports because they:
a.) Assumed the validity of “complex climate models”, and
b.) Ignored natural variability in Earth’s heat source – the Sun.
My concerns are summarized in the paper, “Earth’s Heat Source – The Sun”, Energy & Environment 20 (2009) 131-144: http://arxiv.org/pdf/0905.0704
The Sun is a variable star, and opinions are still divided on its origin, composition, and source of energy, as explained in this brief video clip (<1 min) [1] and this 2001 report to the Lunar & Planetary Conference [2].
1. Cassiopeia A and the Birth of the Sun
2. "The Sun's origin, composition and source of energy"
http://www.lpi.usra.edu/meetings/lpsc2001/pdf/1041.pdf
Again, I appreciate the work you have done to establish this site and I look forward to a frank and polite discussion of the causes for variability in Earth's climate.
With kind regards,
Oliver K. Manuel
Former NASA Principal
Investigator for Apollo
Emeritus Professor of
Nuclear & Space Sciences
I will not comment on Dr. Manuel’s “iron Sun” theory beyond stating that we disagreed about that elsewhere on Science Blog some time ago. But that is off the subject of this thread.
I will comment on his two main reasons for disagreement with the IPCC report:
Reason (a) has a long history, with disagreements between empiricists and modelers underlying much interesting scientific debate, as detailed in Chris Mooney’s insightful book Storm World. The Royal Society report recognizes that but its section on developments in climate science specifically notes “improved methods for simulating the climate system, and increased computer power.”
My response is that modeling has a long history in physical science, going back to the Ancients’ attempts to understand planetary motion and continuing through today’s well-established techniques in computational physics. Of course we must always test the validity of our models with real data, and that’s what the Royal Society is talking about as “improved methods.”
I think the report does an excellent job of of describing the strengths and weaknesses of those “complex models,” as Dr. Manuel calls them, and describing the strength of the consensus about their conclusions.
Obviously Dr. Manuel doesn’t consider the improvement in those methods sufficient. The only response to that is that time will tell, since the improvement in both data collection and modeling will continue.
As for (b), my understanding from the Royal Society report is that variation in solar radiation and electromagnetic activity was considered by the IPCC, but “When only natural climate forcings are put into climate models, the models are incapable of reproducing the size of the observed increase in global-average surface temperatures over the past 50 years.”
Finally, one of my major reasons for posting this summary of the report was the cogent statement about how policy decisions almost always have to be made without “perfect knowledge.” We need to weigh the risks of inaction as well as action using the best scientific scenarios we can muster.
I don’t think the climate models are nearly as complex as “the wide variety of interests, cultures and beliefs in society [which] make consensus about such choices difficult to achieve. However, the potential impacts of climate change are sufficiently serious that important decisions will need to be made.
“Climate science – including the substantial body of knowledge that is already well established, and the results of future research – is the essential basis for future climate projections and planning, and must be a vital component of public reasoning in this complex and challenging area.”
Dear Dr. Bortz,
Thank you for your kindness in allowing my post to be viewed and for your very well written and detailed reply.
We agree that ultimately “time will tell.”
Thank you, also for using your considerable talents to help children understand the “fascinating world-wide pattern of ever-changing, yet often predictable, weather.”
http://www.fredbortz.com/WWIntro.htm
Could I persuade you to help communicate the intriguing story of the transformation of subatomic particles from angry, resentful neutrons at the core of the Sun into the beautiful, peaceful world on this Skeptical Swedish Scientists blog?
http://skepticalswedishscientists.wordpress.com/2010/10/01/beautiful-bing/
With kind regards,
Oliver K. Manuel
Sorry, Dr. Manuel, but that blog does not interest me, and I sense an ulterior motive in your compliments and request.
Here’s why:
I have written about neutrons as one of six short volumes in the Library of Subatomic Particles (Rosen, 2004). It’s a high-low set (high-interest, low reading-level) aimed at junior high students.
I have also written about neutrons and other subatomic particles in Physics: Decade by Decade (Twentieth Century Science, Facts On File, 2007), a science history for high school and up.
In The Neutrino and The Quark in the subatomic set and also in the closing chapter of the physics history that includes discoveries in the first decade of this century, I discuss neutrino mode oscillation, a Nobel-Prize winning discovery that you refuse to accept because it undoes one of the main pillars of your Iron Sun theory.
So I suggest we just keep this thread focused on the Royal Society’s valuable summary report and leave your beyond-the-fringe Iron Sun theory out of it. There are plenty of other solar variations that are widely accepted as possibly having relevance to understanding Earth’s climate, so let’s just stick to those.
I’m sorry that I can’t be as complimentary about your work as you have been about mine.
That’s okay, Dr. Bortz.
The nuclear mass data – showing repulsive interactions between neutrons in every nucleus with two or more neutrons – will not change.
When you find time, you may want to examine these data yourself to see if they are in agreement with the stories you have written:
http://www.omatumr.com/Overheads/8a.pdf
You have received great talents for communication, Dr. Bortz. May you continue to use those talents to communicate the wonderful world of science to children.
With kind regards,
Oliver K. Manuel
One correction please, Dr. Bortz:
[NOTE FROM BLOG OWNER: I am inserting my response directly here, after which I consider this subtopic closed. If Dr. Manuel wants to discuss his Iron Sun theory, he needs to get his own blog. We argued this out elsewhere previously, as I noted in response to his first comment.]
It is incorrect to suggest (above) that the science is settled about solar neutrino oscillations: “. . . neutrino mode oscillation, a Nobel-Prize winning discovery that you refuse to accept because it undoes one of the main pillars of your Iron Sun theory.”
1. The Climategate scandal showed that the science of CO2-induced global warming was not settled by the Nobel Prize that was given to Al Gore, the UN’s IPCC, and the army of climatologists championing that questionable claim.
[RESPONSE: That had nothing to do with the Iron Sun theory. Now that the dust has settled, it is clear that the excesses of the scientists in that tempest did not change any data or the consensus view. It did lead to some procedural changes which will no doubt benefit future IPCC reports. Read My Take on “Climategate” for the way I see it. You will note that it contains no incendiary language, unlike Dr. Manuel’s sarcastic reference to “The army of climatologists.”]
2. Physics Professor Janet M. Conrad of MIT states on page 15 of her booklet “Neutrinos Matter” http://www-boone.fnal.gov/about/nusmatter/
“But do neutrinos oscillate? No experiment has proved that they do – at least not to the satisfaction of the very demanding scientific establishment.”
[RESPONSE: That is a very good report written for young readers. However, it appears to have been written in approximately 2001, just about the time that evidence that most physicists considered conclusive came from the Sudbury facility in Canada. She follows the quoted paragraph by looking ahead to other experiments which were expected in projects at Fermilab, her institution, at the time of the writing. Just yesterday, I read a news report that further research is finding oscillation in anti-neutrinos that may differ slightly from that observed in neutrinos, and that may lead to an even deeper understanding of the difference between matter and antimatter as well as other existing puzzles. The phenomenon of neutrino oscillation, which Dr. Manuel continues to deny, is producing some very fruitful physics, indeed.]
3. I knew Raymond Davis, Jr. personally for many years and admired his integrity in reporting that the number of neutrinos that he measured coming from the Sun were less than had been predicted. In my opinion, he shared the 2002 Nobel Prize in Physics for very careful measurements that identified the “Solar Neutrino Puzzle.”
He was very old and feeble by the time he received the Nobel Prize, and he did not (so far as I know) contradict others who interpreted Professor Davis’ results as evidence of neutrino oscillations.
[RESPONSE: This is disingenuous. Davis was feeble, but his mind was not. He traveled to accept the Nobel and delivered a lecture, in which he stated the following:
That seems quite definitive to me.]
4. In 2001 we showed that neutron repulsion in the Sun’s core produces solar luminosity, solar neutrinos, and solar wind Hydrogen in exactly the proportions observed. That same year, one hundred and seventy-eight (178) other scientists co-authored the paper by Q. R. Ahmad et al. [“Measurement of Charged Current Interactions Reduced by 8B Solar Neutrinos at the Sudbury Neutrino Observatory,” Physical Review Letters 87 (2001): 71301-5] and claimed solar neutrino oscillations explained the missing solar neutrinos. Those scientists did not share the Nobel Prize.
[RESPONSE: Davis cited the Ahmad et. al. result in the paragraph quoted. Nowhere in his lecture does he cite Manuel. Since the Nobel Prize is never shared by more than three individuals, and two others besides Davis were included in the citation, there was no room left for Ahmad. The Nobel Prize website states:
In short, Dr. Manuel appears to be struggling to keep his theory alive in spite of Nobel Prize-winning data and interpretations that contradict it. It is no shame to have a well thought-out theory contradicted by the evidence. But it is sad when the creator of that theory refuses to accept the evidence and starts attacking as “feeble” the aging (and now deceased) Nobel Prize winner who stated in his lecture: “In 2002, additional SNO data proved beyond doubt that neutrinos oscillate and that the total neutrino flux agrees with theoretical predictions.”]
With kind regards,
Oliver K. Manuel
[FINAL RESPONSE: This sidetrack is now closed. I will not accept further discussion on it.]
Thanks for providing a link to the Royal Society’s summary.
I agree that it’s best to read the full report, as well as information from other sources.
Nature News has an interesting article about the possibility that the decline in solar activity may be linked to the most recent warming. The article has key quotations from several scientists who view this result in the same way I do. It does not change the main conclusion that human activities are primarily responsible for changes in climate. For example:
The Report says “The size and sustained nature of the observed global-average surface warming on
decadal and longer timescales greatly exceeds the internal climate variability simulated
by the complex climate models.”
Yet the past 50 years has not warmed faster than other 50 year periods in the past! So the models must be wrong.
Ann G writes, incorrectly and without supporting evidence: “Yet the past 50 years has not warmed faster than other 50 year periods in the past!”
Yet immediately following the sentence of the report she highlights is this, which points out how wrong her assertion is (emphasis added):
“Unless this variability has been grossly underestimated, the observed climate change must result from natural and/or human-induced climate forcing.
“When only natural climate forcings are put into climate models, the models are
incapable of reproducing the size of the observed increase in global-average surface
temperatures over the past 50 years. However, when the models include estimates of
forcings resulting from human activity, they can reproduce the increase. The same
result is found, albeit with a greater spread between different models, for the simulation
of observed surface temperature changes for each of the habitable continents
separately.”
In other words, the models match the evidence. Furthermore the current sharp increase in temperature is not only happening but it is attributable to human action, not natural phenomena.