Hypothesis Testing – A Failure In The 2007 IPCC Reports

In my post

Short Circuiting The Scientific Process – A Serious Problem In The Climate Science Community

I wrote

There has been a development over the last 10-15 years or so in the scientific peer reviewed literature that is short circuiting the scientific method.

The scientific method involves developing a hypothesis and then seeking to refute it. If all attempts to discredit the hypothesis fails, we start to accept the proposed theory as being an accurate description of how the real world works.

A useful summary of the scientific method is given on the website sciencebuddies.org.where they list six steps

• Ask a Question
• Do Background Research
• Construct a Hypothesis
• Test Your Hypothesis by Doing an Experiment
• Analyze Your Data and Draw a Conclusion
• Communicate Your Results

Unfortunately, in recent years papers have been published in the peer reviewed literature that fail to follow these proper steps of scientific investigation. These papers are short circuiting the scientific method.

In the recent report

“Climate Change Assessments, Review of the Processes & Procedures of the IPCC“ 

within the section titled

IPCC’s Evaluation of Evidence and Treatment of Uncertainty

it is written [boldface added]

The IPCC uncertainty guidance provides a good starting point for characterizing uncertainty in the assessment reports. However, the guidance was not consistently followed in the fourth assessment, leading to unnecessary errors. For example, authors reported high confidence in statements for which there is little evidence, such as the widely-quoted statement that agricultural yields in Africa might decline by up to 50 percent by 2020. Moreover, the guidance was often applied to statements that are so vague they cannot be falsified. In these cases the impression was often left, quite incorrectly, that a substantive finding was being presented.”

My comment on the publication process in the post

Short Circuiting The Scientific Process – A Serious Problem In The Climate Science Community

fits and can be rewritten as

What the current IPCC assessment process has evolved into, at the detriment of proper scientific investigation, is the inclusion of untested (and often untestable) hypotheses.  The fourth step in the scientific method“Test Your Hypothesis by Doing an Experiment” is bypassed.

It is written in the IAC Review of the IPCC report that

“…the guidance was often applied to statements that are so vague they cannot be falsified.”

This is a correct conclusion and also applies to the predictions decades from now as presented in the 2007 IPCC report.

These also cannot be falsified.

The acceptance of hypotheses as facts in the publication process including the IPCC assessments is a main reason that the policy community is being significantly misinformed about the actual status of our understanding of the climate system and the role of humans within it.

Status Of The Ozone Hole In Antarctica

There is an article in the Fall 2010 NOAA ESRL Fall Newsletter titled

Antarctic Ozone Hole Persists, At Least for Awhile

Excerpts from the article read

Major success in reducing ozone-depleting substances may not pay off in the Antarctic for several more years

Then, in the Antarctic spring (August through October), sunlight-sparked chemical reactions begin eating away at ozone. Scientists start making measurements more often, and by October, Morgan or his colleagues are outside in minus 80°F temperatures about every other day. Morgan and other scientists around the world are watching those data carefully, looking for evidence that the Antarctic ozone hole is beginning to heal after decades of hurt.

There’s scant evidence yet, from the balloon-borne instrumnets or others on the ground and on satellites: At the end of September, total ozone was at its annual low of 122 Dobson units. Typical fall, winter, and summertime levels are 250-300 Dobson units. The worst-of-the-year ozone levels have averaged 108 during the last 24 years.

International scientists contributing to the quadrennial 2010 Ozone Assessment— including many NOAA scientists—have calculated that although global stratospheric ozone may recover by midcentury, the ozone hole in the Antarctic will likely persist longer.

Erroneous Information On The Website “Sourcewatch”

In reading Judy Curry’s very informative post

Uncertainty gets a seat at the “big table”

I went to her listed link on Sourcewatch with respect to her views. Out of curiosity, I looked up my name

Roger A. Pielke Sr

and was disappointed to see the site writes

Roger A. Pielke, Sr. is a global warming skeptic.

As I have repeatedly shown, I am not in any way a “global warming skeptic”. This pejorative characterization of my views in such a sound bite erroneously presents my perspective on the climate system.

My views can be read, for example, in the papers

Pielke Sr., R., K. Beven, G. Brasseur, J. Calvert, M. Chahine, R. Dickerson, D. Entekhabi, E. Foufoula-Georgiou, H. Gupta, V. Gupta, W. Krajewski, E. Philip Krider, W. K.M. Lau, J. McDonnell,  W. Rossow,  J. Schaake, J. Smith, S. Sorooshian,  and E. Wood, 2009: Climate change: The need to consider human forcings besides greenhouse gases. Eos, Vol. 90, No. 45, 10 November 2009, 413. Copyright (2009) American Geophysical Union,

McAlpine, C.A., W.F. Laurance, J.G. Ryan, L. Seabrook, J.I. Syktus, A.E. Etter, P.M. Fearnside, P. Dargusch, and R.A. Pielke Sr. 2010: More than CO2: A broader picture for managing climate change and variability to avoid ecosystem collapse. Current Opinion in Environmental Sustainability, 2:1–13, DOI 10.1016/j.cosust.2010.10.001,

and

my testimony

Pielke, R.A. Sr., 2008: A Broader View of the Role of Humans in the Climate System is Required In the Assessment of Costs and Benefits of Effective Climate Policy. Written Testimony for the Subcommittee on Energy and Air Quality of the Committee on Energy and Commerce Hearing “Climate Change: Costs of Inaction” – Honorable Rick Boucher, Chairman. June 26, 2008, Washington, DC., 52 pp

If other presentations of viewpoints are as incorrectly reported as mine, Source Watch should be a website to avoid.

New Insight Into Cloud-Aerosol Interactions Within The Climate System

There is an interesting article in NOAA ESRL Fall Newsletter  by Linda Joy titled

 Oscillating Clouds

This article presents yet another example of the diversity of human and natural climate forcings and feedbacks.  Excerpts from the article are

Rain clouds within a large cloud field respond to signals from other clouds, much like chirping crickets or flashing fireflies on a summer night, according to a new ESRL-led study. Published in Nature in August,the finding has significant implications for our understanding of climate change.

Graham Feingold (CSD) and his colleagues showed for the first time that interactions between certain types of neighboring clouds can result in synchronized rain patterns within a large cloud system.

The scientists say that their findings point to a significant influence of particulate matter, or aerosols, on the large-scale structure of clouds and, therefore, on climate change. Scientists have long known that aerosols can influence local rain formation and block solar energy from reaching the Earth’s surface—for an overall surface cooling effect.

However, until recently, the scientific community has not considered the self-organization that results from these effects. Computer simulations for this study indicate that high aerosol concentrations favor the formation of large, dense cloud fields with less open space and less rain.

This creates a more reflective cloud pattern and cooling of the surface. Low particulate levels in computer models resulted in rain and the open honeycomb structure with an oscillating pattern. The open honeycomb structure in a large cloud field lets more sunlight reach the surface, and hence results in surface warming.

“Our work also suggests that we should expand our thinking about interactions between aerosols and clouds,” Feingold said. “Integrating our current focus on fundamental physical processes with broader studies on system dynamics could give us a more complete understanding of climate change.”

Geoengineering – The Perpetuation Of Myths

Update (pm November 10 2010): To make sure my post is clear, this post comments on just two parts of an otherwise excellent overview of the issues associated with geoengineering.  The article is very informative in overviewing the approaches and the issues of geoengineering.  My last paragraph should not have been specifically critical of the Economist, as the article does effectively discuss the concerns with geoengineering. It is other media that has generally not properly reported on this subject. I have edited the last paragraph of my post to clarify.

There is an informative summary of geoengineering in an Economist article in their November 6 2010 article titled (subscription required)

“Lift-off”

The article does provide a useful summary of a number of geoengineering proposals. However, it also perpetuates myths about climate science. The article includes the text that there is a

“subtle distinction between “global warming” and “climate change”.”

The article itself is inconsistent. In the same paragraph they write

“Double the amount of carbon dioxide in the atmosphere and the average global temperature will go up. Add the right amount of stratospheric sulphur and the temperature will come back down to where it began. There will, in other words, be no net global warming. But though the average temperature is unchanged, the climate is not.”

In the real climate system, global warming and cooling is just one subset of a much broader range of climate issues. There is no “subtle distinction”. 

This was discussed, for example, in my post

Is Global Warming the Same as Climate Change?

In that post, I wrote

“Global warming is defined by a positive accumulation of heat (Joules) in the climate system, of which most occurs in the oceans (see Pielke Sr., R.A., 2003: Heat storage within the Earth system. Bull. Amer. Meteor. Soc., 84, 331-335). While surface temperature as also been used to define this heating, it has a range of problems with its use in this context, as we have discussed in our papers, and in earlier weblogs, with more to follow.

Human-caused climate change, however, involves forcings beyond the radiative forcing of the well-mixed greenhouse gases. As summarized in the 2005 NRC report, this includes the multiple influences of aerosols and of biogeochemically active gases, and land-cover changes. The regional changes from these forcings must be considered, even if there were no global warming from these forcings.

By conflating the terms “global warming” and “climate change”, we misinform policymakers, by leading them to believe that the radiative effect of the well-mixed greenhouse gases is the only major forcing of human-caused climate change. It is not. Dealing with climate change is a much more difficult issue than is captured by focusing on global warming.”

In Chapter 1 of my son’s book, The Climate Fix, this broader viewpoint is discussed in his section “Carbon dioxide is Important, but Climate Change Involves Much More”.

They also write with respect to geoengineering that it

“might have political ramifications—even though both countries come closer to their original climates with the other’s optimal level of geoengineering than with no geoengineering at all.”

The use of the term “original climate” perpetuates the misconception that the climate has some constant level in the absence of human intervention. This is an erroneous view as we demonstrate in our paper

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

where we conclude that

“The Earth’s climate system is highly nonlinear: inputs and outputs are not proportional, change is often episodic and abrupt, rather than slow and gradual, and multiple equilibria are the norm.”

Until the broader media (and the policymakers) recognize the real complexity of the climate system, and the unknown risks of geoengineering, such articles such as presented in the Economist will mislead with respect to the dangers of deliberate large scale intervention into the climate system. We already have a number of inadvertant human interventions (e.g. landscape change, aerosol emissions, CO2, etc) whose effects we still do not adequately understand.

My Comments On The Andy Lacis Post On CO2 As A Climate Thermostat

Andy Lacis has posted two guest contributions on my weblog;

Guest Post “CO2: The Thermostat That Controls Earth’s Temperature” By Andy Lacis

Further Comment By Andy Lacis On CO2 As A Climate Thermostat

I very much appreciate this collegial interaction.

Today, I want to comment on his conclusions.

First, I agree with Andy’s conclusion that if CO2 were removed from the Earth’s atmosphere, the climate system would rapidly cool. I also concur that CO2 is a first order climate forcing and is a non-condensing greenhouse gas forcing.

The more interesting question, however, is how this applies both to how the Earth’s climate system actually evolved, and how incremental increases in CO2 above what was present in pre-industral times alter the climate.

With respect to the early Earth atmosphere, CO2 was emitted from volcanic eruptions but so was water vapor. The two acted together to warm the climate. Indeed, this is one explanation proposed to explain the warm, wet period in the earlier atmosphere of Mars and Venus. While, the model experiment presented by Andy and colleagues is quite interesting, it does not reflect the real climate system.

The second issue is, of course, directly relevant to our future climate. As I posted in

Comment On The Science Paper “Atmospheric CO2: Principal Control Knob Governing Earth’s Temperature” By Lacis Et Al 2010

we have examined the effect of incremental increases in CO2 (and water vapor) as described in detail in

Relative Roles of CO2 and Water Vapor in Radiative Forcing

Further Analysis Of Radiative Forcing By Norm Woods

In regards to the effect of an incremental effect on radiative flux of an increase in the atmospheric concentration of CO2, there is an informative figure at Watts Up With That in a post by David Archibald titled The Logarithmic Effect of Carbon Dioxide. The figure is from 2006 by Willis Eschenbach which was posted  on Climate Audit.

What is of importance to our future climate is the added downwelling radiative fluxes as given by the green and black lines. The Lacis and colleagues study examined the effect of the radiative forcing from red line.

The issue with respect to our future climate is how will it be altered in response to these incremental increases, part of which (particularly in the humid parts of the world) overlaps with water vapor absorption).

In terms of how environmentally and societally important resources are altered, as I have often posted on (e.g. see), in terms of climate, this involves how droughts, floods, tropical cyclones, heat waves, etc are altered. This means  the focus should be on alterations in regional ocean and atmospheric circulations, mesoscale weather patterns, and so forth rather than on trends in the global average surface temperatures.  The addition of CO2 is one factor (both radiatively and biogeochemically) but is not the single “control” of these climate metrics. 

The  equilibrium temperature of Earth is just one of these metrics, and, indeed is not adequate to explain how regional and local climate could change. In fact, even with respect to global warming and cooling, the use of ocean heat content is a much more robust way to diagnose these climate system heat changes than a global average surface temperature trend, as discussed most recently in

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

Andy’s posts (and paper) do clearly show that

” there is a clear demonstration that without the radiative forcing provided by the non-condensing GHGs, the terrestrial greenhouse effect collapses because there is no structural temperature support to restrain the current climate water vapor from condensing and precipitating.”

However, there needs to be a recognition that the human influence on the climate system, including global warming and cooling, involves much more than the non-condensing greenhouse gases, and that the role of natural climate forcings and variability remain incompletely understood. We have discussed this in our paper

Pielke Sr., R., K. Beven, G. Brasseur, J. Calvert, M. Chahine, R. Dickerson, D. Entekhabi, E. Foufoula-Georgiou, H. Gupta, V. Gupta, W. Krajewski, E. Philip Krider, W. K.M. Lau, J. McDonnell,  W. Rossow,  J. Schaake, J. Smith, S. Sorooshian,  and E. Wood, 2009: Climate change: The need to consider human forcings besides greenhouse gases. Eos, Vol. 90, No. 45, 10 November 2009, 413. Copyright (2009) American Geophysical Union.

I invite Andy to discuss where he agrees, and where he disagrees, with our conclusions and recommendations in the above paper.

An Insightful Review By Brendan Barrett Of The Book Authored By Roger A. Pielke Jr – The Climate Fix: What Scientists and Politicians Won’t Tell You About Global Warming

There is an informative review of

The Climate Fix: What Scientists and Politicians Won’t Tell You About Global Warming by Roger A. Pielke Jr

by Brandan Barrett of the United Nations University as posted on my son’s weblog. The review is

What kind of climate fix would you prefer?

 With respect to the perspective that we have urged be adopted in our article

Pielke Sr., R., K. Beven, G. Brasseur, J. Calvert, M. Chahine, R. Dickerson, D. Entekhabi, E. Foufoula-Georgiou, H. Gupta, V. Gupta, W. Krajewski, E. Philip Krider, W. K.M. Lau, J. McDonnell,  W. Rossow,  J. Schaake, J. Smith, S. Sorooshian,  and E. Wood, 2009: Climate change: The need to consider human forcings besides greenhouse gases. Eos, Vol. 90, No. 45, 10 November 2009, 413. Copyright (2009) American Geophysical Union.

this review further emphasizes this view in the text

“Pielke’s approach to climate science and policy-making is based on pragmatism and common sense. He accepts that CO2 influences the climate system, perhaps irreversibly, but points out that even if we succeed in reducing CO2 concentrations in the atmosphere to a low level, “we would not have solved the larger challenge of addressing human influences on the climate system”. Put simply, stabilizing CO2 emissions in the atmosphere would not stop climate change if other human influences remain unaddressed (e.g., deforestation, urbanization, desertification, atmospheric aerosols, etc.).”

The entire review (and the book) are worth reading.

Further Comment By Andy Lacis On CO2 As A Climate Thermostat

Andy Lacis sent me a follow up his guest post

Guest Post “CO2: The Thermostat That Controls Earth’s Temperature” By Andy Lacis

 which I have presented below with his permission.

Roger,

Thanks for the post. It looks very good. No doubt you will be receiving a variety of comments on it.

I am pleased that both Roy Spencer’s and your initial comments were basically that “there is really nothing that is particularly new” in our Science paper, for that would be precisely Jim Hansen’s opinion. Of course Jim Hansen would go further and say that there is nothing that is particularly new about proclaiming CO2 to be control knob that governs the temperature of Earth, since he has been saying that for years.

Roy felt that we were engaged in “circular” reasoning by ASSUMING(?) that water vapor and clouds were feedbacks, hence no surprise about the greenhouse effect collapsing when the non-condensing greenhouse gases are zeroed out.

I am not personally involved with the GCM evaporation and condensation of water vapor treatment. (I think that is Tony Del Genio’s job.) But it is my impression that evaporation and condensation of water vapor in the GCM is all physics based, with perhaps some coefficients based on field campaign observations. Nothing that could be interpreted as an “assumption”.

One of my objectives in writing the Science paper was to make a clear distinction between global warming (which can be understood as a cause and effect problem) and global climate change, which includes the much less well understood natural (unforced) variability on inter-annual and decadal time scales, the well documented 11-year solar variability and sporadic volcanic activity.

Since the natural variability and solar cycle forcing produce fluctuations about the global equilibrium temperature, they make no long term trend contribution (except that for a short climate record, they make it difficult to extract the global warming trend due to GHG increases from the climate record by statistical means).

Accordingly, there is a clear demonstration that without the radiative forcing provided by the non-condensing GHGs, the terrestrial greenhouse effect collapses because there is no structural temperature support to restrain the current climate water vapor from condensing and precipitating. Since atmospheric CO2 accounts for about 80% of the non-condensing GHG forcing, we thus conclude that CO2 acts as a thermostat  in controlling the equilibrium temperature of Earth.

Andy

I  invited Roy Spencer to comment, and he referred me to his post

http://www.drroyspencer.com/2010/10/does-co2-drive-the-earths-climate-system-comments-on-the-latest-nasa-giss-paper/

My comments on Andy’s guest posts will appear tomorrow.

Diminishing Returns From Multi-Decadal Global Climate Model Simulations

I have posted that the NSF is funding grants which as part of (or all) of their focus is to provide multi-decadal global and regional climate model projections; i.e. see

The National Science Foundation Funds Multi-Decadal Climate Predictions Without An Ability To Verify Their Skill.

The NSF is also perpetuating an erroneously narrow view of the climate system, as I posted in

Comments On An NSF Webcast On “Will Clouds – The Wild Card of Climate Change – Speed Or Slow Warming?” By David A. Randall.

These claims and projections are based on global climate models.

Judy Curry, on her weblog Climate Etc has very effectively summarized the diminishing scientific responses from the use of these models in her post

Decision making under climate uncertainty: Part I

where she wrote

“So it seems like we are gearing up for much more model development in terms of higher resolution and adding additional complexity. Yes, we will learn more about the climate models and possibly something new about how the climate system works.  But  it is not clear that any of this will provide useful information for decision makers on a time scale of less than 10 years to support decision making on stabilization targets, beyond the information presented in the AR4.”

I agree with this viewpoint.  This culture of using models as the tool to communicate to policymakers is an inappropriate and misleading use of the scientific method. I also discussed this misuse of models in my post

Comments On Numerical Modeling As The New Climate Science Paradigm

where Dick Lindzen is quoted

“In brief, we have the new paradigm where simulation and programs have replaced theory and observation, where government largely determines the nature of scientific activity, and where the primary role of professional societies is the lobbying of the government for special advantage.”

Hopefully, the NSF (and other agencies) will soon realize that most of this funding is a waste of taxpayers money and could be better spent on other research uses in climate and elsewhere.

New “American Meteorological Society [AMS] Policy Statement On Inadvertent Weather Modification” Adopted

The American Meteorological Society has approved a new policy statement. It is presented below. This statement is further recognition of the correctness of the need for a broader view of the human role in the climate system, as we dicussed in our article

Pielke Sr., R., K. Beven, G. Brasseur, J. Calvert, M. Chahine, R. Dickerson, D. Entekhabi, E. Foufoula-Georgiou, H. Gupta, V. Gupta, W. Krajewski, E. Philip Krider, W. K.M. Lau, J. McDonnell,  W. Rossow,  J. Schaake, J. Smith, S. Sorooshian,  and E. Wood, 2009: Climate change: The need to consider human forcings besides greenhouse gases. Eos, Vol. 90, No. 45, 10 November 2009, 413. Copyright (2009) American Geophysical Union.

The statement is

AMS Policy Statement on Inadvertent Weather Modification

 This statement highlights the causes and possible effects of inadvertent weather modification[1] at local and regional scales due to aerosol[2] and gas emissions[3] and to changes in land use.  The known effects can have unanticipated and often undesirable socioeconomic consequences.  This statement assesses the impacts of inadvertent weather modification and suggests potential respective actions.

The climatic effects of greenhouse gases (GHGs) have been summarized by the AMS Information Statement on Climate Change.  This policy statement, however, highlights the key understanding of anthropogenic effects on weather in order to support effective decision making for emission controls, alternate water resources, severe-storm preparedness, and climate-change mitigation and adaptation strategies.  Further, understanding anthropogenic effects on weather is important to improve short-range and longer term weather predictions.

 1. Status of inadvertent weather modification 

This section summarizes the current knowledge of the physical processes affecting weather modification as a result of changes in land use, aerosol and gas emissions.

 a. Aerosol radiative effects

 By partially blocking solar radiation from heating the surface, air pollutants lower surface heating and evaporation rates.  This slows vertical air motions, and hence causes slower dispersal rates of air pollutants, suppresses formation of convective clouds and precipitation.  Reduced surface evaporation has major implications for the global hydrological cycle and how it responds to the combined forcing of GHGs, land use change, and aerosol pollution.  In addition, surface deposition of dark aerosols accelerates ice-melt rates, hence affecting water resources.  While these conclusions are based on sound physical meteorology, many of these effects are yet to be quantified.

b. Cloud mediated effects of aerosol

 Aerosols act mostly as cloud-drop condensation nuclei (CCN), and some of them as ice nuclei (IN), both of which change cloud radiative and precipitation properties in complex ways.  Over oceans, emissions from fossil-fuel-burning ships produce tracks, observed to dramatically influence the extent and persistence of local shallow cloud cover, reducing the amount of solar radiation received at the surface and enhancing the amount reflected back to space.  Aerosols also suppress precipitation from shallow or short-lived clouds (e.g., orographic cap clouds). Their impacts on deep convective clouds are much less certain, but are of potentially great importance.  Recent research suggests that, depending on meteorological conditions, aerosols can either increase or decrease rainfall from such clouds.  In warm moist atmospheres, aerosols often invigorate deep convective clouds, usually resulting in greater electrical activity, stronger damaging winds, and a greater likelihood of flash floods.  Studies indicate that aerosols might also modulate the intensity of tornadoes and hurricanes.

c. Changes in land use

 One example of significant land use change is the rapid global increase in urbanization and its associated changes in land surface properties and topography that create “urban heat islands” and urban barrier effects that perturb regional air flows, which thus redistributes precipitation, runoff, and flood risk over and around cites. Land-use changes alter surface albedos, as well as surface fluxes of heat, water vapor, and momentum to the atmosphere, and thus modify local and regional atmospheric circulations, which in turn can modify weather. For example, when a forest is removed and replaced by an agricultural field, it can result in a significantly different albedo, especially after a snow storm.  Artificial lakes, wind and solar farms also change the surface fluxes and albedo. Such changes also occur indirectly through increases in nitrogen deposition and atmospheric CO₂, which alter leaf area amounts and thus the portioning of latent and sensible heat fluxes.  Poor agricultural practices that favor wind erosion, such as from summer fallow, overgrazing, and deforestation, as well as from tillage, can produce large quantities of dust that absorb and reflect solar radiation which modify clouds and precipitation processes.

 d. Integrated effects

 The cumulative changes in surface and atmospheric heat and moisture profiles modify atmospheric circulation and weather patterns on all scales, including synoptic storm tracks in ways that are just beginning to be explored.  In the aggregate, these changes can affect air quality, ecosystems, and water resources.  The cumulative impacts of inadvertent weather modification may thus result in local or regional-scale climatic alterations superimposed on, and interacting with, natural and GHG-induced climate variability and change. Understanding, still in its infancy, of inadvertent weather modification is thus necessary for understanding the sources, triggers, and response mechanisms of climate change.

2. Mitigation

Mitigation or avoidance, of these unintended impacts requires:

• Application of new knowledge to curtail pollutant emissions and adverse land use changes and to mitigate their impacts.
• Advancement of scientific and engineering understanding to elucidate the causes of atmospheric changes and to lay the foundation of knowledge for countering their adverse impacts.

 Achieving these objectives requires:

• Documentation of anthropogenic weather forcings.
• Process studies (both observations and simulations) of how such forcings affect meteorological conditions.
• Simulations of the extent to which such local and regional forcings influence hemispheric-scale systems, such as the subtropical and polar jet streams. 

3. Adaptation

 Adaptation is necessary when impacts cannot be fully mitigated.  Adaptation to the unavoidable components of unintended weather modification requires:

• Consideration of environmental impacts of inadvertent weather modification as part of development and planning processes, e.g., crop adaptation, management practices, and water utilization.
• Implementation of strategies to enhance depleted water resources in response to reduced precipitation (e.g., through desalination).
• Evaluation and planning of public response to risks from inadvertent weather modification that can influence severe weather events.  

4. Recommendations

 High-priority research and new technological capabilities are required to improve understanding of the impacts of inadvertent weather modification.  These might include:

• Further use of satellite remote sensing of land, trace gas, aerosol, cloud, and precipitation properties.
• Enhanced documentation of emissions of aerosols and their precursors; their chemical evolution; radiative properties; CCN and IN activity; and their transport and deposition.
• Expanded in situ measurements of aerosol–atmosphere and land-atmosphere interactions over a range of cloud regimes, from fair weather to severe convective storms and to hurricanes.
• Detailed simulations of these processes at a hierarchy of scales, up to global.

These research efforts on unintended weather modification should be recognized as addressing parts of the broader question of climate variability and change, which crosses geopolitical boundaries.  As was the case of acid rain and stratospheric ozone depletion, national and international frameworks should be developed for addressing the related environmental and ethical issues for inadvertent weather modification.

---

[1] Inadvertent weather modification is the unintended consequence of an act, either on purpose or accidentally, that results in changes in the weather. 

[2] An aerosol is a suspension of solid or liquid particles in a gas.  Atmospheric aerosols can have natural or anthropogenic sources, the latter primarily through the combustion of fuels, but also from blowing dust due to degradation of land surfaces, particularly in semi-arid regions.  The large difference in geographic locations between sources and sinks (in deposition areas) and the variety of physical and chemical processes affecting them, lead to a large spatial variability in aerosol concentration, size distribution, and composition.  Aerosols are removed by gradual fall due to gravity (dry deposition) or precipitation (wet deposition), and almost all have a tropospheric half life from a few days to a few weeks.  Evidence exists that aerosols modify weather systems, so that the aggregated changes could affect regional systems.

[3]  Trace gases that result in noticeable atmospheric effects, and that are considered as a group in this statement include: carbon dioxide, methane, carbon monoxide, sulfur dioxide, chlorofluorocarbons, tropospheric ozone, nitrous oxide, and nitrogen oxide.  These gases have natural and/or anthropogenic sources.  .