Monthly Archives: September 2005

A New Integrated Climate/Environmental Activity: the Northern Eurasia Earth Science Partnership Initiative (NEESPI)

The recognition that environmental, including climate, issues require an integrated assessment is being implemented by NEESPI. This is an international effort including USA and Russian scientific involvement. The Science plan states,

“Climatic changes in Northern Eurasia (20% of the global land mass) interact and affect the rate of the Global Change through atmospheric circulation and through strong biogeophysical and biogeochemical feedbacks. These feedbacks arise from changes in surface energy, water, and carbon budgets of the continent. How this carbon-rich, cold region component of the Earth system functions as a regional entity and interacts with and feeds back to the greater global system is to a large extent unknown. Thus, the capability to predict future changes that may be expected to occur within this region and the consequences of those changes with any acceptable accuracy is currently uncertain and hampers projections of the Global Change rates.

One of the primary reasons for this lack of regional Earth system understanding is the relative paucity of well-coordinated, multidisciplinary and integrating studies of the critical physical and biological systems. Furthermore, the critical measurements needed to monitor changes in the area are not available. NEESPI strives to understand how the land ecosystems and continental water dynamics in northern Eurasia interact with and alter the climate system, the biosphere, the atmosphere, and the hydrosphere of the Earth. Its overarching Science Question is: How do we develop our predictive capability of terrestrial ecosystems dynamics over Northern Eurasia for the 21st century to support global projections as well as informed decision making and numerous practical applications in the region?

The foci of the NEESPI research strategy are the deliverables, which support both national (primarily the U.S. Climate Change Science Program, CCSP) and international science (e.g. International Geosphere Biosphere Program, IGBP) programs.”

The NEESPI mission statement reads,

“The Northern Eurasia Earth Science Partnership Initiative (NEESPI) will identify the critical science questions and establish an international program of coordinated research on the state and dynamics of terrestrial ecosystems in northern Eurasia and their interactions with the Earth’s Climate system to enhance scientific knowledge and develop predictive capabilities to support informed decision-making and practical applications. ”

This program builds on the recognition that climate is a system involving physical, biological and chemical processes, as we discussed in our July 11th blog entitled “What is climate? Why does it matter how we define climate?”, and as identified by the 2005 National Research Council report , and the International Geosphere-Biosphere Programme.

More details on NEESPI are available at http://neespi.org/.

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Comment on Webster et al. September 16, 2005 Science Article “Changes in Tropical Cyclone Number, Duration, and Intensity in a Warming Environment”

The September 16,2005 article by Webster et al. in Science concludes that there has been a large increase in the number and proportion of hurricanes reaching Saffir-Simpson category 4 and 5 hurricanes over the past decade. They report that these increases have taken place while the number of tropical cyclones and tropical cyclone days has decreased in all basins except the North Atlantic.

This is a clearly written article by very well-respected scientists. There are, however, several substantive issues with the study. First, an informative figure illustrating the maximum potential for hurricanes as a function of SST was described by a 1988 paper by Robert Merrill entitled “Environmental Influences on Hurricane Intensification” (see Figure 2 in that paper). This research was completed for the Atlantic hurricane region, but the SST thresholds should be the same for the other basins. As presented in that paper, Category 4 and 5 hurricanes require sea surface temperatures (SST) of over 27°Celsius. Thus the criteria that should be examined are anomalies in SST that result in increases of temperatures above the 27°C criteria. Category 5 hurricanes require temperatures 28°C. Has the area of SST above these thresholds increased, for example?

The Webster et al. Science article actually present a range of SST values during the respective hurricane seasons for the different hurricane basins in Figure 1 of their paper. These range from around 29.5°C for the north Indian Ocean to around 27.5°C for the north Atlantic and eastern Pacific Ocean basins. Such an analysis suggests that regardless of SST temperature trends, the north Indian Ocean should have a greater porportion of Category 4 and 5 hurricanes. Clearly, there are other factors besides SST that determine the ability of the tropical cyclones to attain Category 4 and 5 intensities as we discussed in Pielke, R.A., Jr. and R.A. Pielke, Sr., 1997: Hurricanes: Their nature and impacts on society. John Wiley and Sons, England, 279 pp, and Pielke, R.A., 1990: The hurricane. Routledge Press, London, England, 228 pp. Indeed, it is rare for the hurricane to attain its maximum intensity due to other limitiations. The Science article is silent on the relation between the different SSTs in the different hurricane regions with respect to the proportion that reach category 4 and 5 intensities.

The major limitations that prevent hurricanes from reaching their full potential includes vertical wind shear, dry air intrusion, and less than optimal outflow aloft in the upper portion of the hurricane circulation. In idealized hurricane modeling it is relatively easy to create hurricanes that attain their maximum intensity, since these limitations are not prescribed in the model initialization or boundary conditions. In the real world, however, one or more of these limitations almost always exists (fortunately!). Hurricane Katrina is an example where a particularly effective outflow aloft, moist tropical air, and a lack of vertical wind shear, along with the elevated SSTs, pemitted the cyclone to attain a category 5 intensity.

In Nicholls, M.E., and R.A. Pielke, 1995: A numerical investigation of the effect of vertical wind shear on tropical cyclone intensification. 21st Conference on Hurricanes and Tropical Meteorology, AMS, Boston, April 24-28, Miami, Florida, 339-341, we investigated the role of shear on hurricane intensification. In Eastman, J.L., M.E. Nicholls, and R.A. Pielke, 1996: A numerical simulation of Hurricane Andrew. Second International Symposium on Computational Wind Engineering, 4-8 August 1996, Fort Collins, CO , we investigated the skill in the simulation of a Category 4 and 5 hurricane. A clip of our model simulation of Hurricane Georges is available from Video Clip of Hurricane Georges (8 Megabytes). We suggest that the use of high resolution models of hurricane intensification as influenced by SST anomolies should be a high priority in addressing the issue of their role, relative to other influences, on hurricane intensification. It is only with fine-scale hurricane model simulations of real world systems, that are able to resolve the eyewall region of the hurricane, that we can adequately address the issue of the relative role of the spatial pattern and magnitude of SSTs on the intensity that they attain.

As another issue, why use 5-year running averages? Tropical cyclones respond to the SST that exists when they occur. The analysis should have correlated tropical cyclone intensity with the specific SST values for each event. The conclusions of the authors would be more robust if they evaluated the Category 4 and 5 hurricanes on a case by case basis with respect to the ocean SST temperatures and SST anomolies over which the hurricanes moved.

Finally, the same analysis, as shown by Pat Michaels (Global Warming and Hurricanes: Still No Connection), when applied to an earlier time period (starting in 1945) than in the Webster et al. Science study, indicates that a high proportion of Category 4 and 5 hurricanes also occurred then. Webster et al. is clear as to why they chose to use the more recent era with the better data coverage. However, coverage for the Atlantic basin, for instance, is quite good since 1945 and should have been assessed against the more recent time period. The Michaels communication ideally should have been submitted to Science as a comment, so that Webster et al. would need to respond. Nonetheless, it highlights an important issue that needs to be resolved as to whether Webster et al. are analyzing the upward portion of a cyclic behavior of hurricane intensities or a real much longer-term trend.

Webster et al. do appear to recognize this issue. The Science article concludes with the statement (referring to the trend towards more frequent and intense hurricanes),

“This trend is not inconsistent with recent climate model simulations that a doubling of CO2 may increase the frequency of the most intense tropical cyclones, although the attribution of the 30-year trends to global warming would require a longer global data record and, especially, a deeper understanding of the role of hurricanes in the general circulation of the atmosphere and ocean, even in the present climate state”.

This qualification of their work was lost when the news media highlighted in their reports (e.g., see “Experts say global warming is causing stronger hurricanes“).

The National Oceanographic and Atmospheric Administration (NOAA) provides a very valuable current assessment of SST anomolies , which can be directly related to the SST temperature anomolies presented in the Webster et al. paper. For example, for the September 17th data, above average SST temperatures in the Atlantic Ocean hurricane region is evident, as is the cooling to below average where the recent hurricanes have traveled. The analysis also shows a complex spatial pattern of SSTs which further supports the need for the Webster et al conclusions to be assessed with respect to the actual SSTs traversed by the hurricanes. The NOAA data also show that the hurricane region exceeds the threshold for Category 4 and 5 hurricanes, even without additional warming.

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Additional Evidence as to Why Land-Use/Land-Cover Change is a First-Order Climate Forcing

A September 13, 2005 NASA Press release entitled “Tropical Deforestation Affects Rainfall in the U.S. and Around the Globe” reports on recent research work led by Roni Avissar of Duke University that has provided further evidence of the importance of land-use/land-cover change as a first-order climate forcing. As the news release states

“Today, scientists estimate that between one-third and one-half of our planet’s land surfaces have been transformed by human development… Our study carried somewhat surprising results, showing that although the major impact of deforestation on precipitation is found in and near the deforested regions, it also has a strong influence on rainfall in the mid and even high latitudes,” said Roni Avissar, lead author of the study, published in the April 2005 issue of the Journal of Hydrometeorology… Deforestation does not appear to modify the global average of precipitation, but it changes precipitation patterns and distributions by affecting the amount of both sensible heat and that released into the atmosphere when water vapor condenses, called latent heat,” said Avissar. ‘Associated changes in air pressure distribution shift the typical global circulation patterns, sending storm systems off their typical paths.’ And, because of the Amazon’s location, any sort of weather hiccup from the area could signal serious changes for the rest of the world like droughts and severe storms.”

This work is discussed in detail in Avissar et al. 2005.

This new research supports the conclusions summarized in the NASA publication entitled Local or Global Problem? . As reported in that publication with respect to the global climate implications of land-use/land-cover change,

“Though their results drew national media attention from many sources, all the scientists involved in the research agree that the scientific arena is where the results should be evaluated. Pielke hopes these results will convince scientists to give the land cover-climate connection more attention. In the past, he has been frustrated by the lack of attention to the topic.

Gordon Bonan is a climate modeler for the National Center for Atmospheric Research in Boulder, Colorado. `It’s definitely true that historically, the emphasis in global climate change research has been on other climate forcings-greenhouses gases, solar variability, aerosols-and that the role of land cover has been neglected. Roger’s work, his persistence, has really played a large role in bringing people around to the importance of it.’ Bonan thinks people are finally beginning to listen.

So far, what research has been done on the global-scale influence of land cover change on climate seems to suggest it plays a minor role. That’s not surprising, says Bonan, considering how small the Earth’s land surface is compared to its oceans and that our most common metric for climate change is global mean temperature. Even significant changes in the temperature where we live can get ‘washed out’ (at least for a while) in the global average of a world mostly covered by oceans.

‘Nobody experiences the effect of a half a degree increase in global mean temperature,’ Bonan says. ‘What we experience are the changes in the climate in the place where we live, and those changes might be large. Land cover change is as big an influence on regional and local climate and weather as doubled atmospheric carbon dioxide-perhaps even bigger.’ That’s the idea Pielke says he has been trying to get across for years. ‘Climate change is about more than a change in global temperature,’ he says. ‘It’s about changes in weather patterns across the Earth.’ Even if it turns out that land cover change doesn’t significantly alter the globally-averaged surface temperature of the Earth, it’s still critically important. ‘The land is where we live. This research shows that the land itself exerts a first order [primary] influence on the climate we experience.’

The full text of this May 17 2005 NASA publication article is available at the link above.

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Land Cover/Land Use Change Session March 7-11, 2006 at the Association of American Geographers (AAG) Annual Meeting

CALL FOR PAPERS

Special Session(s) “Land Cover/Land Use Change”

Association of American Geographers (AAG) Annual Meeting
March 7-11 2006
Chicago, IL

Sponsors: Climate Specialty Group, Cryosphere Specialty Group

Local to regional land surface processes related to land cover/land use change represent an important first-order forcing of climate variability. Changes in land cover due to urbanization, agriculture, and engineering projects have important consequences for vegetation, soil moisture, sensible and latent heat fluxes, air temperature, precipitation, atmospheric circulation, the distribution of frozen ground (in high latitude/altitude regions), etc. In areas where rapid and extensive alterations to the land surface have occurred, such as China, parts of North America and Europe, high-latitude areas, as well as many other regions, the analogous land surface processes can have
widespread climatic and environmental consequences. This special session will therefore focus on the contribution of surface processes related to land cover/land use change on climate variability at a variety of spatial scales: local, regional, and potentially hemispheric and global.

To participate in this session, please register for the meeting and submit your abstract online at the AAG web site (http://www.aag.org/). Then, please e-mail your abstract along with your Presenter Identification Number to one/both of the conveners (below) by Tuesday, October 11. Feel free to also e-mail prior to abstract submission if you have questions about this session.

Oliver W. Frauenfeld, oliverf@colorado.edu
CIRES/National Snow and Ice Data Center
University of Colorado at Boulder

Rezaul Mahmood, rezaul.mahmood@wku.edu
Dept. of Geography and Geology, and Kentucky Climate Center
Western Kentucky University

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Wind Changes over Time and Space as a Climate Metric to Diagnose Temperature Trends

In Pielke et al. 2001: Analysis of 200 mbar zonal wind for the period 1958-1997. J. Geophys. Res., 106, D21, 27287-27290, we demonstrated that temporal and spatial trends in upper tropospheric winds can be used to diagnosis the trends in the tropospheric temperatures below the level of the wind observations. This concept uses what is called the “thermal wind relation” and is a robust, well-established relationship between the change of wind with altitude and the horizontal temperature gradient.

In that paper, we showed as an example, that a surface (1000 hPa) to 200 hPa layer-mean horizontal north-south temperature gradient of 1 degree Celsius (using an average latitude of 43 degrees) would produce a 200 hPa wind speed increase of 4.6 meters per second. This means that if there were a 0.1-0.2 degree Celsius decrease in the zonally-averaged gradient between the high- and mid-latitudes over a period of a decade or more, we would see a 0.46-0.92 meter per second decrease in the wind speed over the same time period. Such a magnitude of change in the tropospheric layer-averaged temperatures has been observed (e.g., see http://vortex.nsstc.uah.edu/data/msu/t2lt/uahncdc.lt).

There is an important message to these numbers. First, the wind speed change that must result from the observed reduction of the zonally-averaged layer-average temperature gradient is quite small in comparison to the typical upper tropospheric wind speeds associated with synoptic weather features that can be 50 meters per second and more. This small trend places the use of global- and zonally-averaged tropospheric temperature trends in an appropriate perspective, in that they are a poor metric to diagnose climate variability and change.

Secondly, in order to assess the accuracy of satellite and radiosonde assessments of tropospheric temperature trends, the monitoring of the trends in wind speed and direction provides an independent metric to assess the temperature trends. If the Arctic troposphere is really warming relative to the mid- and tropical latitudes, we should see a weakening of the zonally-averaged wind speeds. However, for the period 1958-1997, in
Chase et al. 2002: A proposed mechanism for the regulation of minimum midtropospheric temperatures in the Arctic. J. Geophys. Res., 107(D14), 10.10291/2001JD001425, we actually found that the 200 hPa winds had become somewhat stronger at higher latitudes.

The finding of the relatively small magnitude of observed zonally- and globally- averaged tropospheric temperature trends with respect to the upper tropospheric winds further illustrates why we need to focus on regional tropospheric temperature changes. Figure 11 in Pielke et al. (2005), shows spatial trends for 1979-2001 in the 300 hPa winds from the NCEP and ERA-40 Reanalyses. Areas with relatively large anomalies are diagnosed. It is the larger regional trends that have the much more direct effect on our weather. The stronger winds across the north Pacific, for example, are just one example of a trend in regional circulation patterns that directly affect the climate of North America.

Such regional assessments of tropospheric temperature trends should be a major initiative within the IPCC and other climate assessments. This needs to be completed on seasonal as well as annually averaged time scales. Our July 28, 2005 blog on What is the Importance to Climate of Heterogeneous Spatial Trends in Tropospheric Temperatures? provides further discussion as to why the regional spatial scale is so important to our understanding of climate variability and change.

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Why is Vegetation Type a First-Order Climate Forcing?

As shown in Figure 1-1 in the 2005 National Research Council report, flora and fauna are climate forcings. A new paper which has just appeared (see Sturm et al. 2005: Changing snow and shrub conditions affect albedo with global implications. J. Geophys. Res., 110, G01004, doi:10.1029/2005JG000013) provides a further quantification of this effect where shrub abundance in the Arctic is increasing. The authors attribute this to a general temperature increase in the region, and suggest that the tundra to shrub conversion further enhances an increase in Arctic temperatures. This occurs because the shrubs have a lower albedo than does the tundra. This specific climate forcing was discussed in the 2005 National Research Council report (see topic 3 ), as well as in several of our papers (Eugster et al. 2000: Land-atmosphere energy exchange in Arctic tundra and boreal forest: available data and feedbacks to climate. Global Change Biology, 6, 84-115; McFadden et al. 2001: Interactions of shrubs and snow in Arctic tundra: Measurements and models. In: Soil-Vegetation-Atmosphere Transfer Schemes and Large-scale Hydrological Models, IAHS Press, Wallingford, Oxfordshire, UK,IAHS Publ. no 270, 317-325; and Liston et al. 2002: Modelled changes in arctic tundra snow, energy and moisture fluxes due to increased shrubs. Global Change Biology, 8, 17-32.)

There are remaining important issues with respect to this study. While the authors attribute tundra to shrub conversion to an increase in temperature, the conversion may also be influenced by the biogeophysical and biogeochemical effect of the observed increased atmospheric concentration of carbon dioxide over the last several decades. Shrubs may preferentially grow with respect to tundra when the carbon dioxide concentrations are higher. Indeed, the authors recognize that a range of vegetation/soil feedbacks need to be investigated before it can be definitively concluded that the tundra to shrub conversion is a general arctic (and therefore global) warming effect.

This study clearly illustrates, however, that vegetation type change even in the natural system is a first-order climate forcing and represents another global heat change effect (global warming is discussed in our August 29th blog). While the role of arctic vegetation in the carbon budget has been extensively investigated, its role in the surface energy budget has not. This new research further demonstrates why we need to look beyond the radiative forcing of carbon dioxide, methane, and the other well-mixed greenhouse gases if we are going to be able to understand global warming and climate change in general.

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A Perspective on Weather and Climate Science by S. Raghavan

S. Raghavan, retired Deputy Director-General of Meteorology of the India Meteorological Department, has written a valuable and very insightful essay on the role of meteorologists in society. Although he recognizes that he is not a climate “expert”, his essay equally applies to climate scientists, as is evident in the text. The article is part of the May 2005 issue of “BREEZE” the newsletter of the Indian Meteorological Society, Chennai Chapter. See also here.

He writes that, with respect to meteorological phenomena;

“Politicians and administrators as well as the public have to evaluate the impact on society of the various phenomena and take decisions in the face of uncertainties. Apparently scientific but incorrect or sensational information is often fed to them. The meteorologist has therefore a responsibility in bringing a correct appreciation of the nature of the meteorological phenomena and the factors which determine their impact, on the part of politicians, administrators and society in general and in removing misconceptions.”

He further states that “A much misunderstood phenomena is “global climate change”.” He discusses the complexity of climate change which has not been properly communicated to politicians.

This essay also illustrates that there are eminently qualified meteorologists of international stature, such as Dr. Raghavan, who are not asked to present their perspectives on climate issues. The article that he wrote, unfortunately, will not have wide dissemination. We need, however, to involve more of the climate science community of the caliber of Dr. Raghavan into the discussion of the science and policy issues, in order to assure a balanced presentation of climate science, which, has been seriously lacking up to the present.

S. Raghavan is also an author with A.K. Sen Sarma of the Chapter entitled “Tropical cyclone impacts in India and neighborhood” in Pielke, R.A., Jr. and R.A. Pielke, Sr., Editors, 2000: Storms, Volumes I and II, Routledge Press, London. His work is obviously of significance in the context of the impacts of Hurricane Katrina in the United States.

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