Monthly Archives: February 2006

What is Global Warming?

This topic has been discussed several times on the Climate Science weblog (e.g. see ). With the current emphasis on this issue in the media (e.g. see Climate scientists issue dire warning ), it is worth stating what global warming, as a concept in physics, means.

Global warming is the addition of heat to the climate system. The unit of measure (its metric) is in Joules. Most of the reported global warming has been in the oceans in the mid-latitude Southern Hemisphere ocean (see Willis, J.K., D. Roemmich, and B. Cornuelle, 2004: Interannual variability in upper ocean heat content, temperature, and thermosteric expansion on global scales. J. Geophys. Res., 109, C12036, doi: 10.1029/2003JC002260. )

As stated in the Willis et al paper,

“”Maps of yearly heat content anomaly show patterns of warming commensurate with ENSO variability in the tropics, but also show that a large part of the trend in global, oceanic heat content is caused by regional warming at midlatitudes in the Southern Hemisphere.”

This heating

“…centered on 40S is spread more uniformly over the water column and warms steadily throughout the entire time series…”

This is for the period mid-1993 through mid-2003.

They further find that, with respect to the current rate of warming (as compared with the Levitus et al earlier data)

“….the warming rate in the early 1970s is comparable to the present rate…..With the present time series, it is therefore not possible to identify whether the recent increase in ocean warming is due to an acceleration of heat uptake by the ocean or is simply decadal variability”.

As I wrote in my September 9 2005 weblog

“A significant portion of the warming is at depth. The portion of this heat that is a depth below the thermocline is not readily available to heat the atmosphere above or to contribute to enhanced evaporation of water vapor from the ocean surface. This heat is ‘sequestered for an unknown period of time.'”


“….global warming has significant spatial variations. Global warming is not a more-or-less uniform warming spread across the oceans. Such a spatially complex warming pattern further supports the claim that a multiple set of climate forcings, in addition to the more homogeneous radiative forcing of the well-mixed greenhouse gases, is altering our climate. The reconstruction of the observed temporal evolution of the spatial pattern over the last several decades by the global climate models remains an unrealized goal.â€?

To justify the claims of a catastrophic impact from global warming, one must show how this heat addition to the climate system results in such dramatic climate consequences. The use of a global average surface temperature clearly does not provide the rigor of scientific cause and effect that is promoted in the media.

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Further Comment on the Feddema et al. (2005) Science paper “The Importance of Land-Cover Change in Simulating Future Climates”

The Climate Science weblog has commented on the excellent Feddema et al Science paper entitled “The Importance of Land-Cover Change in Simulating Future Climates ” (see , see , and see ).

In response to several e-mails between Dr. Feddema and I, I recommended the following approach to move beyond the metric of a global average surface temperature trend in order to assess the significance of the climate response to land use/land cover change;

“The first thing that is needed is the determination of what metric(s) should be used to determine the relative effects of “global warming” and of the more inclusive term “human caused climate change”. The global mean surface temperature trend has become an icon for this purpose. However, as I will discuss in my NCAR ASP seminar on Wednesday [December 14, 2005] (and have published on), it has major unresolved issues regarding its robustness.

Moreover, it is an inadequate metric to describe how we are altering the climate system, as was emphasized in the 2005 NRC report . The global mean temperature trend, even if it were accurately evaluated, does not inform us how the spatial patterns in the atmosphere, oceans and other components of the climate system are changed as a result of human intervention in the climate system.

We have already proposed two new metrics; one is based on the global averged redistribution of surface sensible and latent heat flux due to LULC change (see Pielke Sr., R.A., G. Marland, R.A. Betts, T.N. Chase, J.L. Eastman, J.O. Niles, D. Niyogi, and S. Running, 2002: The influence of land-use change and landscape dynamics on the climate system- relevance to climate change policy beyond the radiative effect of greenhouse gases. Phil. Trans. A. Special Theme Issue, 360, 1705-1719),

while the other is based on the globally-averaged redistribution of aspects of the water cycle such as precipitation (see Pielke, R.A. Sr., and T.N. Chase, 2003: A Proposed New Metric for Quantifying the Climatic Effects of Human-Caused Alterations to the Global Water Cycle. Presented at the Symposium on Observing and Understanding the Variability of Water in Weather and Climate, 83rd AMS Annual Meeting, Long Beach, CA, February 9-13, 2003).

By running the PCM with each human climate forcing turned on in separate runs, and in combinations, the relative influences of the different forcings can be compared with respect to these metrics.

This approach addresses our hypothesis that LULC change (and also the diverse effects of aerosols and the biogeochemical effect of doubled CO2) have a greater effect on climate spatial patterns than that due to the radiative effect of a doubling of the well-mixed greenhouse gases. Since these forcings alter the spatial pattern of tropospheric diabatic heating, an analysis of this change, due to the different climate forcings, provides
a direct measure of how the pressure gradient field is altered. The pressure gradient field represents the fundamental dynamics that drive atmospheric circulations. With the PCM you have a excellent model to evaluate these issues by model sensitivity studies.�

Time will tell if these recommendations are considered.

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New Paper on Why We Need to Adopt a Vulnerability Paradigm With Respect to Climate Variability and Change

A paper has appeared on 3 February 2006 in Earth Interactions titled

“Long-Duration Drought Variability and Impacts on Ecosystem Services: A Case Study from Glacier National Park, Montana” by Gregory T. Pederson, Stephen T. Gray, Daniel B. Fagre, and Lisa J. Graumlich

This paper further documents why we need to adopt a vulnerability paradigm as a more effective framework to reduce our exposure to environmental and social risks from climate variability and change, regardless of the relative contribution from natural- and human-climate forcings.

The abstract of the paper reads,

“ Instrumental climate records suggest that summer precipitation and winter snowpack in Glacier National Park (Glacier NP), Montana, vary significantly over decadal to multidecadal time scales. Because instrumental records for the region are limited to the twentieth century, knowledge of the range of variability associated with these moisture anomalies and their impacts on ecosystems and physical processes are limited. The authors developed a reconstruction of summer (June–August) moisture variability spanning A.D. 1540–2000 from a multispecies network of tree-ring chronologies in Glacier NP. Decadal-scale drought and pluvial regimes were defined as any event lasting 10 yr or greater, and the significance of each potential regime was assessed using intervention analysis. Intervention analysis prevents single intervening years of average or opposing moisture conditions from ending what was otherwise a sustained moisture regime. The reconstruction shows numerous decadal-scale shifts between persistent drought and wet events prior to the instrumental period (before A.D. 1900). Notable wet events include a series of three long-duration, high-magnitude pluvial regimes spanning the end of the Little Ice Age (A.D. 1770–1840). Though the late-nineteenth century was marked by a series of >10 yr droughts, the single most severe dry event occurred in the early-twentieth century (A.D. 1917–41). These decadal-scale dry and wet events, in conjunction with periods of high and low snowpack, have served as a driver of ecosystem processes such as forest fires and glacial dynamics in the Glacier NP region.

Using a suite of paleoproxy reconstructions and information from previous studies examining the relationship between climate variability and natural processes, the authors explore how such persistent moisture anomalies affect the delivery of vital goods and services provided by Glacier NP and surrounding areas. These analyses show that regional water resources and tourism are particularly vulnerable to persistent moisture anomalies in the Glacier NP area. Many of these same decadal-scale wet and dry events were also seen among a wider network of hydroclimatic reconstructions along a north–south transect of the Rocky Mountains. Such natural climate variability can, in turn, have enormous impacts on the sustainable provision of natural resources over wide areas. Overall, these results highlight the susceptibility of goods and services provided by protected areas like Glacier NP to natural climate variability, and show that this susceptibility will likely be compounded by the effects of future human-induced climate change.â€?

Since even “natural climate variability can……. have enormous impacts on the sustainable provision of natural resources over wide areasâ€? the prudent approach to reduce the risk is to plan for the reoccurrence of historical- and paleo- extreme events.

As reported on the Climate Science weblog (e.g. see and see ), and in our peer-reviewed papers (e.g. see ), the vulnerability paradigm is a more robust approach to assess the threats associated with climate variability and change than relying on the narrow perspective of the multi-decadal global climate prediction models.

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Why We Need to Focus on Regional Tropospheric Temperature Trends

In the Climate Science Weblog of July 28, 2005 entitled “What is the Importance to Climate of Heterogeneous Spatial Trends in Tropospheric Temperatures?“

it was stated that,

“The 2005 National Research Council report concluded that:

‘regional variations in radiative forcing may have important regional and global climate implications that are not resolved by the concept of global mean radiative forcing.’

And furthermore:

‘Regional diabatic heating can cause atmospheric teleconnections that influence regional climate thousands of kilometers away from the point of forcing.’

This regional diabatic heating produces temperature increases or decreases in the layer-averaged regional troposphere. This necessarily alters the regional pressure fields and thus the wind pattern. This pressure and wind pattern then affects the pressure and wind patterns at large distances from the region of the forcing which we refer to as teleconnections.�

To further communicate the importance of the regional variations in tropospheric temperatures on the weather that we experience, it is useful to refer to the National Center for Environmental Prediction (NCEP) analyses and forecasts where the anomalies in the tropospheric temperatures are analyzed on a daily basis. A particularly effective display of this information is given at a UCAR web site (see RAP , and then click the time period of interest and “500 mb Z-Anomalyâ€?).

The 500 mb Z-Anomaly is dependent on the layer-averaged temperature below the middle troposphere. When the anomaly is below average, the lower troposphere is colder than average, while the lower troposphere is warmer than average when the anomaly is positive.

The assessment of multi-decadal lower tropospheric temperature trends using such anomalies is what we reported on in 2000 in Chase et al: “A comparison of regional trends in 1979-1997 depth-averaged tropospheric temperatures”.

The examination of the NCEP analysis and forecast data shows two main items with respect to the climate:

1. The anomalies are significant in magnitude and are on the regional scale. An average value of the anomalies over the entire analysis grid would be of very little value in terms of weather forecasts.

2. The anomalies almost always have large values of both negative and positive sign. With a warming troposphere we would expect to see a greater predominance of positive anomalies. The assessment in the trends in these regional anomalies should be a high priority for the climate change community.

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Land Surface Change and Carbon Management – Implications for Climate-Change Mitigation Policy

We published in 2003 an article in Climate Policy which needs to be repeated today. This is needed since the approaches reported in the media to address climate change and variability is oversimplifying a very complicated issue (e.g. see). Our paper is

Marland, G., R.A. Pielke, Sr., M. Apps, R. Avissar, R.A. Betts, K.J. Davis, P.C. Frumhoff, S.T. Jackson, L. Joyce, P. Kauppi, J. Katzenberger, K.G. MacDicken, R. Neilson, J.O. Niles, D. dutta S. Niyogi, R.J. Norby, N. Pena, N. Sampson, and Y. Xue, 2003: The climatic impacts of land surface change and carbon management, and the implications for climate-change mitigation policy. Climate Policy, 3, 149-157.

The abstract reads,

“Strategies to mitigate anthropogenic climate change recognize that carbon sequestration in the terrestrial biosphere can reduce the build-up of carbon dioxide in the Earth’s atmosphere. However, climate mitigation policies do not generally incorporate the effects of these changes in the land surface on the surface albedo, the fluxes of sensible and latent heat to the atmosphere, and the distribution of energy within the climate system. Changes in these components of the surface energy budget can affect the local, regional, and global climate. Given the goal of mitigating climate change, it is important to consider all of the effects of changes in the terrestrial vegetation and to work toward a better understanding of the full climate system. Acknowledging the importance of land-surface change as a component of climate change makes it more challenging to create a system of credits and debits wherein emission or sequestration of carbon in the biosphere is equated with emission of carbon from fossil fuels. Recognition of the complexity of human-caused changes in climate should not, however, be used as an excuse to avoid actions that would minimize our disturbance of the Earth’s environmental system and that would reduce societal and ecological vulnerability to environmental
change and variability. ”

This paper was written as part of the output from a September, 2001, workshop at the Aspen Global Change Institute. , and shows that a broad based consensus can be achieved when an open process of diaglog is permitted. The diverse group of authors are given below:

Gregg Marland, Environmental Sciences Division, Oak Ridge National Laboratory, USA,
Roger A. Pielke Sr., Department of Atmospheric Science, Colorado State University, USA,
Mike Apps, Canadian Forest Service, Natural Resources Canada,
Roni Avissar, Department of Civil and Environmental Engineering, Duke University, USA,
Richard A. Betts, Met Office, Hadley Centre for Climate Prediction and Rresearch,UK,
Kenneth J. Davis, Department of Meteorology, Pennsylvania State University, USA,
Peter C. Frumhoff, Union of Concerned Scientists, USA,
Stephen T. Jackson, Department of Botany, University of Wyoming, USA,
Linda A. Joyce, Rocky Mountain Research Station, U.S. Forest Service, USA,
Pekka Kauppi, University of Helsinki, Finland,
John Katzenberger, Aspen Global Change Institute, USA,
Kenneth G. MacDicken, Center for International Forestry Research, Indonesia,
Ronald P. Neilson, USDA Forest Service, USA, rneilson@fs.fed.usJohn O. Niles, Energy and Resources Group, University of California, Berkeley, USA,
Dev dutta S. Niyogi, Department of Marine, Earth, and Atmospheric Sciences, N. C. State University, USA,
Richard J. Norby, Environmental Sciences Division, Oak Ridge National Laboratory, USA,
Naomi Pena, Pew Center on Global Climate Change, USA,
Neil Sampson, The Sampson Group Inc., USA,
Yongkang Xue, Geography Department, University of California, Los Angeles, USA,

The Conclusion of the paper states,

“There has been widespread acceptance that at some level sequestering carbon in the terrestrial biosphere has the same effect on atmospheric CO2 as does reducing emissions of CO2 (IPCC, 2000). We point out that whereas the immediate effect on atmospheric CO2 may be the same, the effect on the Earth’s climate is not the same. Climate is the interaction of all of the components of the Earth system and it includes the solar and infrared radiation and sensible and latent heat fluxes that are all impacted by changes in the Earth’s surface.

Given the goal of mitigating climate change, it is important to consider our influence on all of the system components and to work toward a better representation of the full system. Present mitigation strategies focus on a single factor (greenhouse gas concentrations) and a single spatial scale (global average climate). While these provide a starting point for confronting climate change; climate change involves other factors and other scales. Humans and ecosystems reside in local climates, not in the global average climate.

Science is moving toward an integrated understanding of our climate system. How this understanding will be woven into public policy is not clear. The complexity of climate understanding requires a linkage between science and public policy so that policy can evolve as our understanding increases. The immediate question is how to minimize the vulnerability of ecosystems and human society to climate change and climate variability. To what extent do current climate-policy initiatives, focused on greenhouse gas concentrations, succeed in providing incentive for actions that reduce undesirable human influences on the climate system and increase resilience to climate change? The integrated perspective on climate change described here raises the importance of human-induced land-cover change in global mitigation strategies, but makes comparison with other mitigation strategies more complex. Trying to make present investments in the long-term health and resilience of ecosystems, and trying to make the UN Framework Convention on Climate Change operational and consistent with its stated objectives, thus confronts a variety of complex issues.

Which actions then clearly help to prevent “dangerous anthropogenic interference in the climate system?â€? Reducing greenhouse gas emissions to stabilize or reduce greenhouse gas concentrations in the atmosphere and minimizing loss of existing forests, grasslands, and native ecosystems surely work to minimize human-induced climate change on all scales. We suggest that efforts to restore or mimic the structures and functions of native ecosystems will also generally be consistent with the desire to minimize the human impact on the climate system. And, there are many other environmental, economic, and social values that are important in land management choices. Recognition of the complexity of human-caused changes in climate should not be used as an excuse to avoid actions that will minimize our disturbance of the Earth’s environmental system and that will decrease vulnerability to environmental change and variability. Reductions in net greenhouse gas emissions and land-surface change, for example, represent appropriate approaches to lessen our impact on the environment. Our hierarchy of approaches for integrating land surface changes into climate mitigation strategies offers a significant challenge for the further integration of science and public policy.”

The media and “scientific” assessments that neglect the issues raised in this paper should be interpreted as advocacy publications.

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More on the Surface Temperature Trends in Stable Boundary Layers

On January 23, 2006, this weblog summarized the reasons that there is a warm bias
in the diagnosed global average surface temperature record (see “Why there is a Warm Bias in the Existing Analyses of the Global Average Surface Temperature”). The identification of this bias in the peer reviewed literature provides a challenge to the established dogma that the surface temperature trend data is robust.

This issue is fundamental to the media reports that we are past a “tipping pointâ€? (e.g. see ) with respect to climate change, as the global surface temperature trend is the icon that has been adopted by many in the policy making arena (inappropriately; see There is Confusion on What is Meant Regarding the Terms “Global Warmingâ€? and “Climate Changeâ€? ).

Not only is there a problem with the observational interpretation of the data, there is also a major problem with the multi-decadal climate modeling of this icon. As will be reported in a soon to be published special issue of Boundary Layer Meteorology on the “GEWEX Atmospheric Boundary-Layer Study (GABLS) on stable boundary layersâ€?, most of the surface air temperature increase predicted by climate models occurs during stable atmospheric conditions, and that the climate models poorly represent the stable boundary layer. This special issue will be reported on in the Climate Science weblog in more detail when it appears.

The modeling of the stable boundary layer is so difficult due to the need to accurately represent the interaction of long-wave radiative flux divergence and turbulence. These processes significantly affect the surface temperature trend that is predicted by the models. In stable boundary layers, the turbulence is often intermittent, and the vertical temperature profile complex.

A challenge to the multi-decadal global modeling community, and to the IPCC and CCSP assessments that use this information, is how accurately can they predict the stable boundary layer contribution to surface temperature trends. It is remarkable that policy has been implemented which has not even adequately evaluated this icon of the global warming community.

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There is Confusion on What is Meant Regarding the Terms “Global Warming” and “Climate Change”

In the February 16, 2006 New York Times, there is an article by Andy Revkin that states,

“In a more recent example of possible political pressure at the agency, press officers and scientists cited an e-mail message sent last July from NASA’s headquarters to its Jet Propulsion Laboratory in Pasadena, Calif. It said a Web presentation describing the uncontroversial finding that Earth was a “warming planet” could not use the phrase “global warming.” It is “standard practice,” the message went on, to use the phrase “climate change.'”

The weblog Prometheus discusses this news release today.

I want to add to this discussion by posting a perspective of the use of the two terms “global warming” and “climate change” that was in response to a question from Andy Revkin in August 2005. My answer with respect to where global warming fits within the concept of climate change is posted below;

“On Climate Change

To add even more complication, global warming is only one component of climate change. As discussed in our July 28th blog (What is the Importance to Climate of Heterogeneous Spatial Trends in Tropospheric Temperatures?), it is the alteration of atmospheric and ocean circulations as a result of the diversity of climate forcings which have a larger impact on the climate that we experience, than can be described by the metric of the total climate system heat change. The climate forcing of land-use/land-cover change is just one example of such a climate forcing. As shown in a a variety of papers (e.g., see Chase et al. 2000, 2001 ), there are large regional changes in weather patterns due to landscape change as simulated in the models with implications on whether a region warms or cools, and becomes wetter or drier over time. This occurs despite little global average heat changes associated with land-use/land-cover change, since areas of cooling balance with areas with warming. We can see the importance of atmospheric circulation changes in hurricane tracks. Whether the USA is pummeled by landfalling hurricanes such as Katrina or recurves offshore depends on the regional tropospheric wind field not a global average metric.

Thus we limit the communication to policymakers if we use climate change as a synonym for global warming. Global warming is just one aspect of a much more complicated environmental issue.”

We need to properly define our terms on a scientific basis to effectively communciate with policymakers. A key recognition that was made in the text written above is “global warming is only one component of climate change.”

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