Monthly Archives: June 2006

Comment on the NRC Report “Surface Temperature Reconstructions for the Last 2000 Years”

The Report “Surface Temperature Reconstructions for the Last 2000 Years” has appeared. This Report discusses the IPCC “hockey stick” plot of the multi-century global average surface temperature trends.

When I first saw this plot several years ago, I assumed it would be quickly shown that pasting togther of proxy data with the instrument data for the last few decades is scientifically flawed. These two approaches represent two distinctly different procedures to assess surface temperature trends. However, this hockey stick figure has become an icon for communicating global warming (and climate change, in general) to the public and policymakers.

In the Report, I fail to see an assessment of the following questions:

1. What is the uncertainty associated with the diagnosis of a global average surface temperature trend by pasting the instrument record onto the end of the proxy record? How does proxy data in the last few decades correspond to the measured surface air temperature trends AT THE SAME LOCATIONS?

2. Why is it assumed that “The Earth warmed by roughly 0.6 degrees….during the 20th century..” when we have documented biases in the peer reviewed literature in the assessment of trends in the land surface temperature data (e.g. see “Should light wind and windy nights have the same temperature trends at individual levels even if the boundary layer averaged heat content change is the same?”; “Assessing ‘Global Warming’ with Surface Heat Content”)? In a national assessment, why was such peer reviewed literature ignored?

Ignoring these science questions provides the perspective that the Report is intended to promote a particular perspective on climate science, rather than providing a balanced presentation on the issues. Indeed, the statement in Boston Globe that,

“Our conclusion is that this recent period of warming is likely the warmest in a (millennium),’’ said John Wallace, one of the 12 members on the panel and professor of atmospheric science at the University of Washington”,

clearly shows such a biased view. The Report is a disappointment in not adequately addressing the accuracy of the global surface temperature trend data. Since its accuracy is at the foundation of the entire Report, the absence of such an evaluation very substantially weakens the value of the Report in climate science.

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Impact of Tropical Deforestation on Climate

The Aspen Global Change Institute (AGI) has had excellent meetings in past. In the venue that they used when I attended, a rich diversity of viewpoints on climate science were presented, and subsequently summarized in reports. In this weblog, I want to communicate the main points of a summary of the presentation by Karen L. O’Brien who attended a 1997 meeting on “Elements of Change 1997: Scaling from Site-Specific Observations to Global Model Grids“.

The report on her work entitled “Scales of Change: The Climatic Impacts of Tropical Deforestation in Chiapas, Mexico” is relevant to all areas of the humid tropics. The report concludes that

“General circulation models coupled with atmosphere-biosphere models provide increasing evidence that deforestation can significantly influence the climate at a number of scales.”

Here are several of the bullet summaries based on her research, as extracted from the AGI Report:

1. “In scaling up to higher levels of analysis, emergent properties may appear as a result of synergistic interactions taking place at higher levels of system integration, such as the regional or global scale.”

2. “Tropical deforestation usually results in a mosaic pattern of land cover, and there is evidence that the atmospheric response to a heterogeneous land surface is nonlinear.”

3. “There is a growing recognition that the simulated impacts of deforestation on the climate are regionally specific, in large part due to the different scales of the deforested areas.”

4. “O’Brien’s local scale analysis shows a strong tendency for maximum daily temperatures to decrease at climate stations exhibiting high deforestation, particularly to the northeast of the station.”

5. “There is no clear-cut distinction between “forested” and “deforested” stations. Instead, deforestation appears as a continuum among stations.”

6. “There is a tendency for minimum temperatures to increase at some of the stations, but the majority of stations show no change.”

7. “Annual precipitation totals are highly variable with no clear trends, contrary to a widespread perception that rainfall has decreased in the Selva Lacandona.”

8. “The amount of deforestation in the full circle surrounding the climate stations seems to be less important than the location of the clearings. ”

9. “These results do not contradict conclusions based on global modeling studies, but they do indicate that the issue of local-scale changes is more complex than the models suggest.”

10. “Environmental change research demands an integrated approach that recognizes the complexity of scale, as well as the importance of analyzing data at a number of scales.”

I also recommend her excellent book,
“Sacrificing the Forest : Environmental & Social Struggle in Chiapas”,

which clearly exemplifies why the vulnerability paradigm is such a powerful assessment tool for policymakers.

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Further Evidence of the Biases in Surface Temperature Measurements At Poorly Sited Locations

An important new paper has appeared which further documents major concerns regarding the use of surface air temperature data to assess long term temperature trends. The June 30, 2006 International Journal of Climatology paper by by Rezaul Mahmood, Stuart A. Foster and David Logan is entitled “The Geoprofile metadata, exposure of instruments, and measurement bias in climatic record revisited“(subscription required).

The abstract reads,

“Station metadata plays a critical role in the accurate assessment of climate data and eventually of climatic change, climate variability, and climate prediction. However, current procedures of metadata collection are insufficient for these purposes. This paper introduces the GeoProfile as a model for documenting and visualizing enhanced spatial metadata. In addition to traditional metadata archiving, GeoProfiles integrate meso-scale topography, slope, aspect, and land-use data from the vicinity of climate observing stations ( main.html). We describe how GeoProfiles are created using Geographical Information Systems (GIS) and demonstrate how they may be used to help identify measurement bias in climate observations due to undesired instrument exposures and the subsequent forcings of micro- and meso-environments. A study involving 12 COOP and US Historical Climate Network (USHCN) stations finds that undesirable instrument exposures associated with both anthropogenic and natural influences resulted in biased measurement of temperature. Differences in average monthly maximum and minimum temperatures between proximate
stations are as large as 1.6 and 3.8 °C, respectively. In addition, it is found that the difference in average extreme monthly minimum temperatures can be as high as 3.6 °C between nearby stations, largely owing to the differences in instrument exposures. Likewise, the difference in monthly extreme maximum temperatures between neighboring stations are as large as 2.4 °C. This investigation finds similar differences in the diurnal temperature range (DTR). GeoProfiles helped us to identify meso-scale forcing, e.g. instruments on a south-facing slope and topography, in addition to forcing of micro-scale sitting.”

Among the conclusions in the text are the statements that,

“In an ideal setting, a well sited station results in recorded temperature values that are free of bias and
representative of the broader region. However, the presence of bias in temperature observations has long been recognized. While troublesome, it is still possible to analyze climate variability and assess climate change if the site and locality of a station remain unchanged, and the bias is stationary over time. Collectively, our analyses of temperature data from 12 COOP stations (including two that are part of the USHCN) show complex patterns of pairwise temperature variability and suggest the influence of multiple sources of bias that are nonstationary over different timescales.

Evidence of bias can be found in temperature records from both urban and rural sites. All of the urban based stations in this study are located in towns and cities ranging in population from just over 2000 to nearly 20 000. Certainly, the small scale of urbanization limits the traditional UHI bias. However, research in urban micrometeorology (Arnfield, 2003) identifying the impacts of diverse surfaces on energy budgets, energy exchanges, and small-scale advection suggests that even a limited urbanization is relevant when examining the potential impacts of the site and locality characteristics of instrument exposures on temperature observations. While rural settings are generally considered to provide superior settings for climate observations, our research reveals that the micro-environments of rural stations are often similar to those of urban stations. Specifically, they are often characterized by the presence of paved surfaces and brick and block buildings in close proximity to instrument installations. In some cases, superior sites are available nearby.”

“Collectively, these empirical results raise questions about the interpretation of climatological time series associated with arbitrarily selected stations from the NWS COOP network, including stations that are part of the USHCN.”

This new peer reviewed paper provides even more evidence that the claims in Chapter 3 of the CCSP Report “Temperature Trends in the Lower Atmosphere: Steps for Understanding and Reconciling Differences“ of a robust multi-decadal surface temperature trend assessment is erroneous.

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Complexity of Current Glacial Advance and Retreat

The media reports on “global warming” often highlight widespread glacial retreat as evidence of worldwide warming. For instance, see the quote from the Arizona Daily Star,

“As evidence of global warming’s effects, Gore shows Alaska’s rapidly retreating glaciers…”

However, in a recent trip to southeast Alaska where I revisited several glaciers that I had viewed several decades ago, it is clear that the issue is more complex than indicated by such news releases. The Margerie Glacier in the northwest corner of Glacier Bay National Park, for example, was in nearly the same place as it was 16 years ago. Southeast of the Park,, the Mendenhall Glacier near Juneau had clearly retreated since I visited yet using the display at the Visitor Center, the northern front the glacier had not changed its position significantly since 1995.

The National Park Service, in their Offical Map and Guide for Glacier National Park states that

“Glacial retreat continues today on the bay’s east and southwest sides, but on its west side, two glaciers are advancing.”

This is not the type of information that is reaching the news media. All of Alaska’s glaciers are not “rapidly retreating”.

In a search on the web, other examples of glacial advance in Alaska are presented. This includes the summaries listed below,

The United States Forest Service at Tongass National Forest reports that

“Hubbard Glacier, one of the few advancing glaciers in the world, could block the entrance to Russell Fiord near Yakutat, Alaska, creating a large ice-dammed lake…. Hubbard Glacier retreated to over 1000 feet from Gilbert Point in summer 2005 and remains a considerable distance from closing. The glacier does not start its annual advance until February and USGS will reinitiate monitoring at that time. Glaciologists predict that Hubbard Glacier will again block Russell Fiord; however they cannot predict when this event may happen. Hubbard Glacier has advanced and retreated in the past and there is evidence of a previous overflow event into the Situk River. ”

A Cyberwest magazine article writes that,

“A University of Alaska Fairbanks glaciologist reported that a glacier in the central Alaska Range has surged, or advanced rapidly. The McGinnis Glacier surge was observed by Martin Truffer, associate professor of physics with UAF, who noticed that the lower portion of the glacier was covered in cracks, crevasses and ice pinnacles — evidence that the glacier recently moved forward at higher-than-normal rates. ”

A similar pattern of complexity in glacial advance and retreat has been observed outside of Alaska. A March 2005 paper by Chinn et al in Geografiska Annaler entitled “Recent Glacier Advances in Norway and New Zealand: A Comparison of their Glaciological and Meteorological Causes” has the following abstract,

“Norway and New Zealand both experienced recent glacial advances, commencing in the early 1980s and ceasing around 2000, which were more extensive than any other since the end of the Little Ice Age. Common to both countries, the positive glacier balances are associated with an increase in the strength of westerly atmospheric circulation which brought increased precipitation. In Norway, the changes are also associated with lower ablation season temperatures. In New Zealand, where the positive balances were distributed uniformly throughout the Southern Alps, the period of increased mass balance
was coincident with a change in the Interdecadal Pacific Oscillation and an associated increase in El Niño/Southern Oscillation events. In Norway, the positive balances occurred across a strong west-east gradient with no balance increases to the continental glaciers of Scandinavia. The Norwegian advances are linked to strongly positive North Atlantic Oscillation events which caused an overall increase of precipitation in the winter accumulation season and a general shift of maximum precipitation from autumn towards winter. These cases both show the influence of atmospheric circulation on
maritime glaciers.”

The Chinn et al paper is very informative. It provides a discussion of why we need to focus on regional climate change and variability with respect to glacial retreat and advance. The use of a global average concept (such as global warming), and the statement claiming that Alaska’s glaciers are rapidly retreating, is an erroneous oversimplification of the complex behavior of glaciers.

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Arctic Tree-line and the Polar Front: Guest Weblog by Professor Harvey Nichols

Professor Harvey Nichols is on the faculty of the Department of Ecology and Evolutionary Biology.

His research interests are summarized on the University of Colorado-Boulder website as

“Research Interests: Paleo-ecology, arctic and alpine environments, and global change, with emphasis on pollen analysis (palynology) as a method of reconstructing past vegetation and climate to understand the present environment and to act as background for current environmental concerns. The program has involved over twenty expeditions into the arctic to study past movements of the arctic tree-line driven by climatic change, which now provides an important perspective and test for the Greenhouse Hypothesis. An agreement has been reached with the Central Siberian Botanical Institute to exchange American and Russian students to explore the Siberian and North American arctic tree-line for signs of atmospheric warming in a long-term research project.”

With his extensive expertise in tree line studies, I invited Professor Nichols to publish one of his very insightful poster presentations on the Climate Science weblog. His knowledge on this subject will inform all of us on the climate metric of high latitude tree line, and its dynamics over time.

The December 2000 American Geophysical Union poster is entitled “Arctic tree-line and the Polar Front: climatic changes past and present, possible sunspot linkage” , and the abstract reads,

“The arctic tree-line is sensitive to climatic changes as indicated by paleoecological studies and it is predicted by global circulation models to respond strongly to greenhouse warming. My Northern Canadian studies of tree-line reproduction in black and white spruce spanning two decades demonstrate a widespread switch from infertility due to cold summers (1960’s-1970’s) to pollen and cone production (1990’s), in line with climatic warming predictions. Ecotonal cone formation is usually sporadic and localized, but this large scale reproductive shift, along a 1500 km transect, suggests widespread biospheric response to climatic warming since the 1970’s across much of the Northwest Territories. Labrador, not included in the original study, has experienced a delayed response in a region of prolonged cooling. In 1995 I tested the hypothesis by examining arctic tree-line at a transect of sites in western Siberia where ecotonal larch trees were reproducing sexually, and greenhouse studies confirm that enough seeds were viable to allow seedling colonization of the tundra. Siberian colleagues noted that the age structure of these “tree-islands” based on tree-ring studies suggested that a recent warming response was identifiable. In 1996 I examined a series of “tree-islands” in the tundra of northern Yakutia in northeast Siberia. All the larch trees bore cones, but greenhouse studies show that seed viability was very low, possibly due to a persistent cold trough in the upper Westerlies. These Siberian studies (at 27 sites) represented only a modest fraction of the Eurasian treeline, but the widespread fertility at so many locations, plus the extensive Canadian evidence, and Fenno-Scandinavian findings, suggest that the predicted polar warming may be responsible, with Labrador and Yakutia showing lagging responses corresponding to troughs in the atmospheric Rossby waves.”

The paper and supplemental material is available at Arctic Tree-line and the Polar Front: Changes Past and Present, Possible Sunspot Linkage.

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Some Controversial Results on the Radiative Forcing of Our Climate System as Extracted from Model Results for the AMIP-2 and IPCC-FAR and for the Radiation Climatologies of the ISCCP-FD and GEWEX-SRB

An interesting seminar was presented at Colorado State University on June 8 2006 by Dr. Ehrhard Raschke of the University of Hamburg, Germany. The seminar title reads,

“Some Controversial Results on the Radiative Forcing of Our Climate System as Extracted from Model Results for the AMIP-2 and IPCC-FAR and for the Radiation Climatologies of the ISCCP-FD and GEWEX-SRB’

with the abstract

“We analyzed only monthly data as provided for the above-mentioned projects and did no further manipulations. This seminar does not report about sensational speculations or new theories on climate change.

Several modeling groups provided data sets describing the radiation fields at both the top and bottom of the atmosphere. Here we compared only values for the incoming solar radiation and found (a) considerable differences in zonal averages (meridional profiles) of up to 15 Wm-2 over both poles during the transitional seasons, (b) systematic regional anomalies of up to ±1 Wm-2, corresponding to seasonal “pulse” of the TSI of 4 Wm-2, (c) different model results on changes of the TSI due to the leap-year and sunspot activity.

ISCCP-FD and GEWEX-SRB radiation products, as they were available until about December 2005 (!) at TOA and at the surface, were simply compared. We found two major errors which need firstly to be removed completely:

(a) ISCCP time series until the data-year 2002 are primarily based on a skin temperature estimate showing a systematic decrease over the entire zone between about 60N and 60S by up to 16 Wm-2, as the inclusion of more recent data, released in April 2006, demonstrates. There are systematic differences in various results on the cloud effect (CRF ) on such products.

(b) GEWEX-SRB data on incoming solar radiation at TOA were often by more than 1% lower than concurrent ISCCP data. This error propagates through all further results on solar radiation budget. It now has been removed in part after a few consultations with the author making the recent data release (2.6) more useful for further studies. Both data sets need a complete reanalysis over both polar regions.

Further, none of both data sets has been validated in detail against satellite measurements of the ERB at TOA. Validations of surface data need a further re-analysis.

We suggest that in future climate studies all model results and climate data sets must be based on the same (well proven) routine for computing the incoming solar radiation at TOA over regions of the earth. Strategies need still development making effective use of ground-based measurements and observations combining the potentials of different networks: e.g. BSRN, ARM, SURFRAD, national and other regional data sets.

`Positive impacts’ of our studies: The GEWEX modelers have invited to report at their workshop on systematic errors in climate models; SRB has done a reanalysis of their solar data during the past 6 months. ISCCP is planning to re-analyze all their radiation products. Our results have been published in Raschke et al., GRL, 2005 and 2006.”

The titles and abstracts of the two papers read,

“How accurate did GCMs compute the insolation at TOA for AMIP-2?”

“Monthly averages of solar radiation reaching the Top of the Atmosphere (TOA) as simulated by 20 General Circulation Models (GCMs) during the period 1985–1988 are compared. They were part of submissions to AMIP-2 (Atmospheric Model Intercomparison Project). Monthly averages of ISCCP-FD (International Satellite Cloud Climatology Project – Flux Data) are considered as reference. Considerable discrepancies are found: Most models reproduce the prescribed Total Solar Irradiance (TSI) value within ±0.7 Wm−2. Monthly zonal averages disagree between ±2 to ±7 Wm−2, depending on latitude and season. The largest model diversity occurs near polar regions. Some models display a zonally symmetric insolation, while others and ISCCP show longitudinal deviations of the order of ±1 Wm−2. With such differences in meridional gradients impacts in multi-annual simulations cannot be excluded. Sensitivity studies are recommended. ”


“An assessment of radiation budget data provided by the ISCCP and GEWEX-SRB”

“The projects ISCCP and GEWEX-SRB compute global data sets of radiation budget components at the top of the atmosphere and at the surface. Time series range from July 1983 to June 2001, and to October 1995, respectively. Comparing monthly averages over broader zones we find that the SRB underestimates the incident radiation at TOA by more than 2–5 Wm−2 over the tropics and up to 40 Wm−2 over polar regions. The ISCCP infrared radiation fluxes near the surface and at TOA, in particular over both polar zones, are higher than those of the SRB. Clouds in the ISCCP appear optically less effective than in the SRB. Interannual and month-to-month variations are observed indicating serious errors in ancillary data. Complete reprocessing is recommended. End products need validation within this large domain in space and time with correlated radiation budget measurements at TOA and at ground. ”

There is a very important conclusion from the Raschke et al. studies. As is stated in the seminar abstract
“We suggest that in future climate studies all model results and climate data sets must be based on the same (well proven) routine for computing the incoming solar radiation at TOA over regions of the earth.”

Regional comparisons would provide a more appropriate quantitative comparison of the multi-decadal global climate models. The ability (or lack of) of regional skill in the global climate model simulations would be crucial information to provide to policymakers. As currently communicated to them, they are presented with regional multi-decadal climate simulations as if they are skillful forecasts for the coming decades. They are not.

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New Christy and Spencer Report on Satellite Temperature Data

A very useful overview of the research of Dr. John Christy and Dr. Roy Spencer of the University of Alabama at Huntsville entitled ” Satellite Temperature Data” was prepared for the Washington Roundtable On Science and Public Policy on April 17, 2006 .

Regardless of your perspective on the climate change issue, it provides an insight and informative summary of their research conclusions. Their talk stated

“Today we are going to show you some of the latest research that has just been published, some that will be published soon and some that hasn’t been published yet, but which gives you an idea where this information is going.”

Among their conclusions are:

“Surface warming has been observed in many regions of the world (not all) in the past century In some of these locations, the warming is more consistent with land-use change, rather than our understanding of greenhouse gas forcing”

“Upper air warming has likely been modest, especially in the tropics Current UAH versions of the data are consistent with balloon-station data while other versions of the satellite data are not.”

The most recent summary of the UAH satellite analyses can be viewed on the UAH website. The current global anomaly (with respect to the periof 1978-present), for example, using the most recent version of their analysis (May 2006) is +0.28C. Their highest global monthly anomaly was +0.77C in April 1998 and the lowest was -0.49C in September 1984. As recently as August 2004 the global anomaly was less than zero.

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