Category Archives: Definition of Climate

Q&A “On GCMs, Weather, and Climate”

 Dan Hughes has sent in a question on climate science (thanks Dan!).

The title is  “GCMs, weather, and climate”, and following is his question.

Hello Professor Pielke,

I have a candidate for Question for the Day.

GCMs do not resolve weather, either spatially or temporally.  Even if sufficient spatial and temporal resolution were used at run time, GCMs are not applied in the same manner as NWP models and codes are applied.  All NWP calculations immediately begin to derivate from reality, and after a relatively short period of time ( a very few days ) the calculated numbers exhibit almost no fidelity to the real world.  The NWP models and codes, knowing that the forecast window into future time is severely limited, inject updated measured information into the calculations.  Obviously, GCMs applied to calculations of future states of the Earth’s climate systems cannot be applied in this manner.

If the above is a correct, but rough, description of the situation, how can the variability seen in the numbers calculated by GCMs be assigned to be weather.  If the numbers are weather, then it is clear that it cannot be the correct weather.  If climate is taken to be the average of weather, how can the average of the weather calculated by GCMs be expected to have any fidelity to actual future states of the Earth’s climate systems.

Kindly let me know if I have presented an incorrect description.

Thank you for taking time to consider this candidate question.

Dan

There is a fundamental difference in how scientists who have prompted the 2007 IPCC WG1 report view climate modeling and how other climate scientists view this modeling. The IPCC perspective is that numerical weather prediction is an initial value problem while  climate prediction is a boundary value problem in which levels of atmospheric CO2 and aerosols are the primary “boundary forcing”.  With this perspective, they claim that changes in the statistics of weather (and other climate features) can be skillfully predicted.

However, our research has shown this is a seriously flawed view as climate prediction is really an initial value problem. It even more complicated than weather prediction since there are more variables that need to be initialized accurately (e.g. ocean temperatures and salinity; land ice depth and area, vegetation type, amount and distribution, etc).  Moreover, there are feedbacks between components of the climate system (e.g. see Figure in NRC, 2005), which become important on time periods of seasons, years and decades.

The need for treating climate as an initial value problem has been documented in a number of publications, including

Pielke, R.A., 1998: Climate prediction as an initial value problem. Bull. Amer. Meteor. Soc., 79, 2743-2746.

Pielke Sr., R.A., G.E. Liston, J.L. Eastman, L. Lu, and M. Coughenour, 1999: Seasonal weather prediction as an initial value problem. J. Geophys. Res., 104, 19463-19479.

Rial, J., R.A. Pielke Sr., M. Beniston, M. Claussen, J. Canadell, P. Cox, H. Held, N. de Noblet-Ducoudre, R. Prinn, J. Reynolds, and J.D. Salas, 2004: Nonlinearities, feedbacks and critical thresholds within the Earth’s climate system. Climatic Change, 65, 11-38. 

Indeed, the broader climate community is starting to come around to this view, as illustrated in the concept of “seamless climate prediction“, which I have discussed on my weblog (e.g. see).

They have a difficult challenge. On time scales longer than perhaps a single season, there is no demonstrated skill in regional predictions.

I hope this addresses your question and appreciate your input!

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What is Climate? Why Does it Matter How We Define Climate?

Originally Posted on July 11, 2005.

The title of this weblog is “Climate Science,” so the first thing we need to do is define “climate.” For many, the term refers to long-term weather statistics. However, on this blog we are adopting the definition that is provided in the 2005 National Research Council (NRC) report where the climate is the system consisting of the atmosphere, hydrosphere, lithosphere, and biosphere. Physical, chemical, and biological processes are involved in interactions among the components of the climate system. Figure 1-1 and 1-2 in the report illustrate this definition of climate very clearly. In the NRC report, climate forcings were extended beyond the radiative forcing of carbon dioxide to include the biogeochemical influence of carbon dioxide, but also a variety of aerosol forcings (see Table 2-2 in the report), nitrogen deposition, and land-cover changes. Each of these forcings has been determined to influence long-term weather statisitics as well as other aspects of the climate.

However, this concept of climate and its alterations by humans, has been generally ignored. The NRC report listed above certainly appears to have been incompletely missed by policymakers. As an example, at the G-8 meeting, the term “climate change” is used interchangably with “global warming.” However, the human influence on climate is much more complex and multi-dimensional than captured by the term “global warming” (see, for example, http://www.climatesci.org/publications/pdf/R-260.pdf; http://www.nap.edu/books/0309095069/html/15.html and http://www.climatesci.org/pdf/R-225.pdf). The term “global warming” is generally used to refer to an increase in the globally-averaged surface temperature in response to the increase of well-mixed greenhouse gases, particularly CO2.

If, however, we are interested in atmospheric and ocean circulation changes, which, afterall is what creates our weather, we need to focus on how humans are altering these circulations. Ocean heat content changes are the much more appropriate metric than a globally-averaged surface temperature when evaluating “global warming” in any case (http://www.climatesci.org.edu/publications/pdf/R-247.pdf).

Thus it matters how we define climate and climate forcing (http://www.nap.edu/books/0309095069/html/15.html). By ignoring a number of the other first-order climate forcings, we are not properly addressing the threat we face in the future, but instead relying on the overly simplistic view of focusing on reductions in carbon dioxide emissions as the way to reduce our “dangerous intervention” in the climate. With respect to the changes of circulations, and therefore, weather, we need to identify and quantify the role of spatially heterogeneous climate forcings such as from aerosols and land-cover change, in addition to the influence of well-mixed greenhouse gases. These heterogeneous climate forcings could represent a more significant threat to our future climate system than the risk of an increase in the atmospheric concentration of CO2.

Hopefully, this blog will stimulate discussion, as well as illuminate reasons why this broader perspective on climate variability and change has been mostly ignored.

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What is Climate Change?

For the next several weeks Climate Science is reposting a number of weblogs that are worth repeating. We have quite a few more readers now than we did when my weblog started. The first reposting appears below.

Originally posted on July 29, 2005.

The different definitions of climate, have done much to confuse policymakers in the discussion of climate science.

The American Meteorological Society (AMS) definition of “climate change” is

“(Also called climatic change.) Any systematic change in the long-term statistics of climate elements (such as temperature, pressure, or winds) sustained over several decades or longer. Climate change may be due to natural external forcings, such as changes in solar emission or slow changes in the earth’s orbital elements; natural internal processes of the climate system; or anthropogenic forcing.”

The AMS defines anthropogenic forcing as

“Human-induced or resulting from human activities; often used to refer to environmental changes, global or local in scale.

The AMS defines the climate system as the

“system, consisting of the atmosphere, hydrosphere, lithosphere, and biosphere, determining the earth’s climate as the result of mutual interactions and responses to external influences (forcing). Physical, chemical, and biological processes are involved in the interactions among the components of the climate system.”

Here we have an inconsistency with the definition even by a very distinguished professional society! Climate, as defined by the AMS, is focused on the atmosphere, while the climate system consists of the atmosphere, hydrosphere, lithosphere, and biosphere. No wonder policymakers misapply this terminology.

As one example of the misuse by policymakers, the Royal Society released the following statement by Lord May:

“The science points to the need for a Herculean effort to make massive cuts in the amount of greenhouse gases that we pump into the atmosphere. So, while this encouraging new deal may play a role in this, it will only be part, and not all, of the solution.”

“But we have serious concerns that the apparent lack of targets in this deal means that there is no sense of what it is ultimately trying to achieve or the urgency of taking action to combat climate change. And the developed countries involved with this agreement must not be tempted to use it as an excuse to avoid tackling their own emissions.”

“All eyes should be on the United Nations Framework Convention on Climate Change in Montreal at the end of November [2005]. Top of the agenda at this meeting should be the initiation of a study into what concentration of greenhouse gases in the atmosphere we can allow without suffering the most catastrophic effects of climate change. This would allow us to plan cuts in worldwide emissions accordingly and provide direction to such efforts to tackle what is the biggest environmental threat we face today.”

Here the conclusion is made that to “combat climate change” we must initiate “a study into what concentration of greenhouse gases in the atmosphere we can allow without suffering the most catastrophic effectsof climate change.”

Ignored in this statement is the role of the other anthropogenic climate forcings that we identified in the National Research Council report.

Lord May, President of the Royal Society, has clearly overlooked a very critical definition of what really constitutes the climate system and what the anthropogenic forcings and feedbacks are that influence climate. He is, unfortunately, cherrypicking climate science.

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New Article In Physics Today Titled “A Broader View Of The Role Of Humans In The Climate System.”

Physics Today has just published an invited opinion piece

Pielke Sr., R.A., 2008: A broader view of the role of humans in the climate system. Physics Today, 61, Vol. 11, 54-55.

The article starts with the text

“The 2007 report from the Intergovernmental Panel on Climate Change Working Group I presents a narrow view of the state of climate science. Attempts to significantly influence regional and local-scale climate based on controlling carbon dioxide emissions alone cannot succeed since humans are significantly altering the global climate in a variety of diverse ways beyond the radiative effect of CO2. The IPCC assessments have been too conservative in recognizing the importance of these human climate forcings as they alter regional and global climate. When the IPCC focuses its policy attention on CO2, it neglects other important aspects of the impact of human activities on climate.”

The conclusion of the article reads

 “Humans are significantly altering the global climate, but in a variety of diverse ways beyond the radiative effect of CO2. Significant, societally important climate change on the regional and local scales, due to both natural and human climate forcings, can occur due to these diverse influences. The result of the more complex interference of humans in the climate system is that attempts to significantly influence regional and local-scale climate based on controlling CO2 emissions alone is an inadequate policy for this purpose. There is a need to minimize the human disturbance of the climate by limiting the amount of CO2 that is emitted into the atmosphere by human activities, but the diversity of human climate forcings should not be ignored.”

The entire article can be read  at http://www.climatesci.org/publications/pdf/R-334.pdf.

 

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A 1,000-year, Annually-Resolved Record of Hurricane Activity From Boston, Massachusetts by Besonen et al.

There is a new paper which uses paelo-data to extend the record of hurricane activity back before the histroical record. The paper is

Besonen, M. R., R. S. Bradley, M. Mudelsee, M. B. Abbott, and P. Francus (2008), A 1,000-year, annually-resolved record of hurricane activity from Boston, Massachusetts,Geophys. Res. Lett., 35, L14705, doi:10.1029/2008GL033950.

with the abstract

“The annually-laminated (i.e., varved) sediment record from the Lower Mystic Lake (near Boston, MA), contains a series of anomalous graded beds deposited by strong flooding events that have affected the basin over the last millennium. From the historic portion of the record, 10 out of 11 of the most prominent graded beds correspond with years in which category 2-3 hurricanes are known to have struck the Boston area. Thus, we conclude that the graded beds represent deposition related to intense hurricane precipitation combined with wind-driven vegetation disturbance that exposes fresh, loose sediment. The hurricane signal shows strong, centennial-scale variations in frequency with a period of increased activity between the 12th-16th centuries, and decreased activity during the 11th and 17th-19th centuries. These frequency changes are consistent with other paleoclimate indicators from the tropical North Atlantic, in particular, sea surface temperature variations.”

The conclusion reads,

“The LML sedimentary record provides a well-controlled and annually-resolved record of category 2–3 hurricane activity in the Boston area over the last millennium. The hurricane signal shows centennial-scale variations in frequency with a period of increased activity between the 12th–16th centuries, and decreased activity during the 11th and 17th–19th centuries. We recognize that the LML record is a single point source record representative for the greater Boston area, and hurricanes that passed a few hundred km to the east or west may not have produced the very heavy rainfall amounts and vegetation disturbance in the lake watershed necessary to produce a strong signal within the LML sediments. Nevertheless, we also note that clear evidence of a secular change in hurricane frequency identified in the LML record is consistent with other lines of evidence that conditions for the development of hurricanes have changed on centennial timescales. Hence, it appears that hurricane activity was more frequent in the first half of the last millennium when tropical Atlantic SSTs were warmer and eastern equatorial Pacific SSTs were cooler than in subsequent centuries.”

This study adds to the clear documentation in the paleo-record that climate is not stationary, and never has been!

Climate Science discussed this recently in the weblog

The Value Of Paleoclimate Records In Assessing Vulnerability to Drought: A New Paper Meko et al 2008

This perspective is also presented in

Rial, J., R.A. Pielke Sr., M. Beniston, M. Claussen, J. Canadell, P. Cox, H. Held, N. de Noblet-Ducoudre, R. Prinn, J. Reynolds, and J.D. Salas, 2004: Nonlinearities, feedbacks and critical thresholds within the Earth’s climate system. Climatic Change, 65, 11-38.

Claims that we “need to stabilize the climate”  illustrate a complete lack of understanding of the actual large variations in time and space of the climate system from natural climate variability.

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Important New Insight into Climate and Energy Policy by Peter R. Hartley and Kenneth B. Medlock III of Rice University

In response to the Climate Science posting entitled Roger A. Pielke Sr.’s Perspective On Adaptation and Mitigation, Peter R. Hartley contacted me with respect to an in-depth assessment of the subject of climate and energy policies and the degree to which they overlap. Professor Hartley is the George and Cynthia Mitchell chair and a professor of economics at Rice University.

He has a James A. Baker Institute for Public Policy Working Paper with colleague Dr. Kenneth B. Medlock III titled

Climate Policy and Energy Security: Two Sides of the Same Coin?

and an excellent powerpoint presentation with the same title, summarizing the key points of their working paper (see).

Climate Science has concluded that the energy and climate issues should be separated, based on the strong scientific evidence that supports the statement below (see) that

  • While natural variations are important, the human influence is significant and involves a diverse range of first-order climate forcings (including, but not limited to the human input of CO2).

The powerpoint by Professor Baker and Dr. Medlock is a very effective overview of their major findings, and presents a valuable and much needed framework to address the issue of the consequences to climate and energy policies if they are not “two sides of the same coin”.

For instance, they ask the question

“How much climate change is natural, how much is attributable to anthropogenic non-CO2 sources, and how much results from the accumulation of CO2?”,

with the conclusion that

“The larger the non-CO2 components of climate change, the stronger the case for mitigation or remediation of damages.”

 Climate Science, and our research group, have been urging a broader perspective to the role of human climate forcings, and the adoption of a more inclusive set of climate metrics than just the global average surface temperature trend (e.g., see  where we propose, as one new metric, a diagnosis of changes in regional climate forcing of atmospheric circulations from human climate forcings).  This broader view has also been presented in the 2005 National Research Council report that is discussed frequently on Climate Science.

The recognition by the economic community of the need to assess the degree of actual overlap between energy and climate policies is very much welcome!

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Summary Conclusions of Climate Science

The Climate Science Weblog has documented the following conclusions:

The needed focus for the study of climate change and variability is on the regional and local scales. Global and zonally-averaged climate metrics would only be important to the extent that they provide useful information on these space scales.

Global and zonally-averaged surface temperature trend assessments, besides having major difficulties in terms of how this metric is diagnosed and analyzed, do not provide significant information on climate change and variability on the regional and local scales.

Global warming is not equivalent to climate change. Significant, societally important climate change, due to both natural- and human- climate forcings, can occur without any global warming or cooling.

The spatial pattern of ocean heat content change is the appropriate metric to assess climate system heat changes including global warming.

In terms of climate change and variability on the regional and local scale, the IPCC Reports, the CCSP Report on surface and tropospheric temperature trends, and the U.S. National Assessment have overstated the role of the radiative effect of the anthropogenic increase of CO2 relative to the role of the diversity of other human climate climate forcing on global warming, and more generally, on climate variability and change.

Global and regional climate models have not demonstrated skill at predicting regional and local climate change and variability on multi-decadal time scales.

Attempts to significantly influence regional and local-scale climate based on controlling CO2 emissions alone is an inadequate policy for this purpose.

A vulnerability pespective, focused on regional and local societal and environmental resources of importance, is a more inclusive, useful, and scientifically robust framework to interact with policymakers, than is the focus on global multi-decadal climate predictions which are downscaled to the regional and local scales. The vulnerability paradigm permits the evaluation of the entire spectrum of risks associated with different social and environmental threats, including climate variability and change.

Humans are significantly altering the global climate, but in a variety of diverse ways beyond the radiative effect of carbon dioxide. The IPCC assessments have been too conservative in recognizing the importance of these human climate forcings as they alter regional and global climate. These assessments have also not communicated the inability of the models to accurately forecast the spread of possibilities of future climate. The forecasts, therefore, do not provide any skill in quantifying the impact of different mitigation strategies on the actual climate response
that would occur.

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Human Impacts on Weather and Climate by W. R. Cotton and R. A. Pielke Sr. Published By Cambridge University Press

As initially announced on Climate Science where a discount is available (and as another plug for our book! :-)) The second edition of our book Human Impacts on Weather and Climate has appeared. There is both a hardback and a paperback version.

The summary of the book published by Cambridge University Press is,

“This new edition of Human Impacts on Weather and Climate examines the scientific and political debates surrounding anthropogenic impacts on the Earth’s climate and presents the most recent theories, data and modeling studies. The book discusses the concepts behind deliberate human attempts to modify the weather through cloud seeding, as well as inadvertent modification of weather and climate on the regional scale. The natural variability of weather and climate greatly complicates our ability to determine a clear cause-and-effect relationship to human activity. The authors describe the basic theories and critique them in simple and accessible terms. This fully revised edition will be a valuable resource for undergraduate and graduate courses in atmospheric and environmental science, and will also appeal to policy makers and general readers interested in how humans are affecting the global climate.

• Includes updated concepts and theories, new observational data, and modeling studies
• A generally non-mathematical presentation of scientific concepts and theories to appeal to a broad range of readers
• Discusses both inadvertent and planned weather modification
Contents

Part I. The Rise and Fall of the Science of Weather Modification: 1. The rise of the science of weather modification; 2. The glory years of weather modification; 3. The fall of the science of weather modification; Part II. Inadvertent Human Impacts on Regional Weather and Climate: 4. Anthropogenic emissions of aerosols and gases; 5. Urban-induced changes in precipitation and weather; 6. Other land-use/land-cover changes; 7. Concluding remarks; 8. Overview of global climate forcings and feedbacks; 9. Climatic effects and anthropogenic aerosols; 10. Nuclear winter; 11. Global effects of land-use/land-cover changes and vegetation dynamics; Epilogue; Index.
Reviews

The reviews that they list are,

“‘Contents-wise this is an excellent book … It is written with great honesty and courage, attacking many of the sacred tenets of weather modification and of climatic doomsday predictions.’ Meteorology and Atmospheric Physics

‘I can recommend the book to anyone concerned to understand the present debates with regard to climate change on both a local and global scale. The style of writing makes for easy reading, and the layout of the book is such that sections of particular interest can be found easily.’ Open University Geological Society Journal

‘… offers a valuable perspective that will be useful particularly for undergraduate courses in earth and atmospheric sciences. Students without a strong grounding in mathematics and physics will find this straightforward account quite approachable and welcome.’ International Journal of Climatology

‘ … a comprehensive, well-written, and highly interesting book. I strongly recommend it to all atmospheric scientists, to students in the atmospheric sciences, and to those in the environmental sciences interested in understanding weather and climate issues.’ Bulletin of the American Meteorological Society”

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Merger Of Air Quality Studies and Weather And Climate Research

I presented a lecture at the 2005 the Golden Jubilee of the EPA/NOAA partnership in Durham, North Carolina entitled “The Partnership of Weather and Air Quality“.

The report version of my talk

Pielke Sr. R.A., 2006: The partnership of weather and air quality – An essay. Atmospheric Science Paper No. 770, Colorado State University, Fort Collins, CO 80523, 44 pp. is now available.

The abstract reads,

“As part of the celebration of the Golden Jubilee of the EPA/NOAA partnership, this paper provides a perspective on the movement towards a merger of the disciplines of weather and air quality science. Also presented are several major conclusions regarding the modeling of atmospheric dispersion, which have resulted in the use of combined knowledge from both disciplines These conclusions include the recognition that dispersion is greater than evaluated from Gaussian models in situations with significant large scale wind flow over heterogeneous landscapes, but overestimated in light wind conditions, particularly in heterogeneous landscapes.

Methodologies are proposed that would improve the ability to model the interactions of weather and air quality. These include the replacement of existing parameterizations with much more computationally efficient look-up-tables, the calculation of the linear and nonlinear components of the models separately, and use of wind tunnel modeling to improve the accuracy of the numerical models.”

The report includes discussion on the merger of research between traditional air quality studies and climate, since atmospheric chemistry and the dispersion of natural and anthropogenic aerosols into the atmosphere are integral components of the climate system [e.g. see the 2005 National Research Council Report: Radiative forcing of climate change: Expanding the concept and addressing uncertainties].

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Climate Science Summary

Climate Science has been posting weblogs since July 2005. This weblog highlights the topic areas and the link to each category.

Climate Change Forcings and Feedbacks

Climate Change Metrics

Climate Models

Climate Science Meetings

Climate Science Misconceptions

Climate Science Op-Eds

Climate Science Reporting

Definition of Climate

Guest Weblogs

Q&A on Climate Science

Vulnerability Paradigm

The Major Conclusions of Climate Science

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