Monthly Archives: March 2007

A Seminar On the Importance of Land Surface Processes On the Global Climate System

I thank Jim Angel, the Illinois State Climatologist, for alerting me to this seminar. While most of us cannot attend, the topic is of considerable interest to us.

ANNNOUNCEMENT

The Illinois State Water Survey Presents
Center for Atmospheric Sciences Seminar

A butterfly flaps its wings: The unintended regional and global
consequences of Amazonian deforestation

Peter Snyder
Department of Atmospheric Sciences
University of Illinois at Urbana-Champaign

Tuesday, April 3 2007 2:00 – 3:00 PM
Illinois Room – ISWS Conference Room
Coffee and Cookies at 1:45 PM

ABSTRACT

Although it has been established that the biosphere has an influence on the atmosphere at local and regional scales, there is widespread disagreement over whether the biosphere is capable of influencing the global climate through large-scale changes to the atmospheric general circulation. Numerous studies have already identified the regional climate response to human modification of the landscape through changes to the biophysical exchanges of energy, water, and momentum between the land surface and the atmosphere. However, we still do not understand whether land use and land cover change are capable of influencing remote regions through teleconnection processes. Furthermore, given a specific surface forcing, it is not entirely clear where the response will occur, how strong it will be, or how large a surface forcing is required in order for a climate response to be felt globally. Tropical deforestation is one example of a surface forcing that has the potential to influence the global climate. Several studies have suggested that significant changes to the Northern Hemisphere climate may occur as a result of selective tropical deforestation in the Amazon basin, yet most of these studies have focused on the climate response in the extratropics with little explanation of the mechanisms responsible for propagating the signal out of the tropics. This has led to disagreement over whether these mechanisms are real or are, in fact, artifacts generated by “noise” in climate models.

I will present results from a coupled atmosphere-biosphere model, CCM3-IBIS (Community Climate Model, version 3 – Integrated Biosphere Simulator), to illustrate the potential influence of theoretical land use and land cover change on the global climate by way of atmospheric teleconnections. The results suggest that pan-tropical and Amazonian deforestation can have a strong influence on the Northern Hemisphere general circulation by way of changes to synoptic-scale dynamics and land-atmosphere feedbacks both in the Amazon and in Asia. The result is a large warming across parts of Asia in boreal winter. While theoretical, this approach illustrates the potentially important processes connecting regional land surface changes in the tropics to climate changes in far-removed regions.

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A New Paper Which Demonstrates The Importance of Land Surface Heat Storage Within The Climate System

I want to thank Jos de Laat of the Royal Dutch Meteorological Institute (KNMI) for alerting me to a new peer reviewed paper on land surface heat storage. It is a very important research contribution as it adopts the appropriate unit of Joules to assess climate system heat changes.

The paper is

Stevens M. B., J. E. Smerdon, J. F. González-Rouco, M. Stieglitz, H. Beltrami (2007), Effects of bottom boundary placement on subsurface heat storage: Implications for climate model simulations, Geophys. Res. Lett., 34, L02702, doi:10.1029/2006GL028546.

The abstract reads,

“A one-dimensional soil model is used to estimate the influence of the position of the bottom boundary condition on heat storage calculations in land-surface components of General Circulation Models (GCMs). It is shown that shallow boundary conditions reduce the capacity of the global continental subsurface to store heat by as much as 1.0 × 10**23 Joules during a 110-year simulation with a 10 m bottom boundary. The calculations are relevant for GCM projections that employ land-surface components with shallow bottom boundary conditions, typically ranging between 3 to 10 m. These shallow boundary conditions preclude a large amount of heat from being stored in the terrestrial subsurface, possibly allocating heat to other parts of the simulated climate system. The results show that climate models of any complexity should consider the potential for subsurface heat storage whenever choosing a bottom boundary condition in simulations of future climate change.”

Important excerpts from the paper, as noted by Dr. de Laat include

“Most GCMs have shallow BBCPs [bottom boundary placements]; Figure 3 can serve as a guide to scale results from other models. For any soil model, if the BBCP is at a depth that is too shallow, the amount of energy stored in the ground may be underestimated. As shown in Figure 3, an increase in BBCP from 10 m to 100 m could result in a four- to five-fold increase in heat storage potential. Furthermore, if there is a feedback mechanism involved between land surface and atmosphere, this unabsorbed quantity of heat may partition to other model subsystems. This is potentially a very important issue for climate models since ascertaining the energy balance of the climate system and all its components is a fundamental requirement for proper evaluations of future climatic trends [Shin et al., 2006, and references therein].”

“As the simulation depth in the 1DSM increases, so too does the potential for subsurface heat storage. For example, for a BBCP at a depth of 10 m, the total heat stored in the subsurface (1.9 × 10**8 J) would be less than one-quarter of the asymptotic value (8.8 × 10**8 J). If scaled over the entire continental surface (1.5 × 10**14 m2), 1.0 × 10**23 J, or 75% of the corresponding asymptotic value (1.3 × 10**23 J) would not be stored in the terrestrial subsurface. This heat, absorbed over 110 years, is more than an order of magnitude greater than the heat absorbed by both the whole atmosphere and continental areas in the latter half of the 20th century [Beltrami et al., 2002; Levitus et al., 2005; Huang, 2006; Beltrami et al., 2006a].”

This is yet another example of why an assessment of heat storage changes in units of Joules should be the appropriate global warming and cooling currency (e.g. see), as well as further evidence of the complexity of the climate system which, unfortunately has been inaccurately discussed in the IPCC assessments. A significant consequence of such deeper land heat storage is that the GCM multi-decadal global climate predictions with shallow lower boundaries are overestimating the land surface temperature trends in response to a positive global radiative forcing.

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Did The Oceans Really Cool Between mid-2003 and mid-2005?

Climate Science has reported numerous times on the paper

Lyman, J. M., J. K. Willis, and G. C. Johnson (2006), Recent cooling of the upper ocean,
Geophys. Res. Lett., 33, L18604, doi:10.1029/2006GL027033.

We have been informed today, however, that a correction will be completed soon on this paper in which the recent cooling trend will be removed.

Climate Science will report on this important new development when it is publically available, as well as the implications with respect to the posting

The Net Climate Feedbacks Must Be A Negative Effect On The Global Average Radiative Imbalance If The IPCC Conclusion Of Net Anthropogenic Radiative Forcings Is Correct

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“Some Fresh Air in the Climate Debate” – An Op Ed by Hendrik Tennekes

On March 28, 2007 the #1 newspaper in Amsterdam De Volkskrant published the following op-ed by Hendrick Tennekes. It reads,

“Recently, IPCC, the climate panel of the United Nations, issued a new report. It focuses on the relation between the emission of greenhouse gases and the rise in globally averaged temperatures in the next one hundred years. A few degrees Centigrade are forecast; in all likelihood this must be ascribed to the burning of fossil fuels. The sea level rise expected by IPCC is on the order of four millimeters per year.

Though it would be easy to write an extensive commentary about these predictions, I feel no need to take issue with IPCC on this point. Taking into account that the worldwide supplies of oil and gas are shrinking, and that Mr. Putin has threatened more than once to shut off the supply of natural gas to Europe, I agree it is necessary to pay more attention to energy-saving technology. Energy policy requires a high priority, both nationally and internationally.

But this does not mean that the climate debate is over now. I just mention a few points that bug me. Assuming that the IPCC numbers are reliable, I find the Doomsday picture Al Gore is painting – a six-meter sea level rise, fifteen times the IPCC number – entirely without merit. IPCC would have substantially lessened the acrimony in the climate debate if it had said so explicitly. It would have credited IPCC also if it had taken issue against the pressure exerted on professionals who doubt the majority view. It is unbecoming that American television weather forecasters who express doubts about global warming are likely to lose their jobs. The planned removal of State Climatologists George Taylor (Oregon), David Legates (Delaware), and Patrick Michaels (Virginia) also does not contribute to an atmosphere of unfettered professional discourse.

I protest the tendency to simplify the climate debate to a matter of fossil fuels, greenhouse gases, and a relatively minor global temperature increase. I protest the rude way geologists and astronomers are shoved aside. Whatever the IPCC staff thinks, it is not at all inconceivable that decreasing solar activity will lead to some cooling ten years from now. And if we look at the climate with a geologist’s eye, we see all kinds of changes that have no discernible origin. In the long run we will enter a new ice age, but in the mean time we may encounter all kinds of ups and downs. The climate is always changing; that happened also when there were yet no people on this planet.

I protest vigorously the idea that the climate reacts like a home heating system to a changed setting of the thermostat: just turn the dial, and the desired temperature will soon be reached. We cannot run the climate as we wish. That is fortunate, because a bad season for farmers may be a boon for the tourist industry, deteriorating conditions for French farmers may mean improving conditions for their Polish colleagues, what is good for winter wheat may make things worse for corn, and so on. We are not dealing with a machine, but with Nature herself, and she is not easily mocked.

I want some fresh air in the climate debate, free of the acrimony surrounding the IPCC report. Fortunately there is plenty room for a breath of fresh air if we stop focusing on greenhouse gases to the exclusion of other matters. We obtain that freedom if we decide to think and act not only globally, but primarily locally. My colleague Roger Pielke Sr , professor emeritus of meteorology at Colorado State University and presently senior scientist at the University of Colorado in Boulder, has been investigating the effects of changing agricultural and forestry practices for many years. He doesn’t stop at commiserating, as so many do, the climatic effects of tropical deforestation. He has demonstrated that increasing irrigation leads to enhanced summer precipitation, for example, in Colorado, Kansas, and Oklahoma. He also charted the effects of southward moving orange plantations on Florida’s microclimate and found that the frost risks for the orange crops had moved southward as fast as the plantations themselves. Local climates can change this much by aggressive farming practices.

Another perspective opened by letting some fresh air in is to consider the concrete vulnerability of societies, in particular those in poor countries, to present climate. This is the vulnerability paradigm proposed by Pielke’s son Roger Jr, who is a political scientist at the University of Colorado, and his colleague Daniel Sarewitz of Arizona State University. If the present climate problems of vulnerable regions are addressed forcefully, then 90% of the future problems there have become manageable. Don’t bother to ponder whether or not climate change is responsible for Katrina’s destructive impact, but state boldly that local, regional, and national authorities have ignored the warnings issued by the US Corps of Engineers for some twenty years. In my little lowlands country something similar has happened. Twenty years of warnings by the engineers in the Ministry of Public Works were thoughtlessly laid aside by the Dutch government. It finally woke up when the storm surge of February 1, 1953 claimed nearly two thousand lives. Then it was too late.

Let me summarize. In the climate, much more is at stake than the probable consequences of a slight temperature rise. The dwindling supplies of gas and oil and the direct effects of greenhouse gases get more than sufficient attention from the global community. But next to that there is a wide, only partially explored territory of local and regional vulnerabilities. Due to the incessant emphasis on the global aspects of the climate problem, this territory does not receive the attention it deserves. That is a shame.

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Impacts Of Land Use/Cover Classification Accuracy On Regional Climate – Another Paper That Documents The Major Role Of The Land Surface Within The Climate System

Another paper has appeared which further demonstrates the first order role of land surface processes within the climate system (thanks to Dev Niyogi for letting us know of this paper; subscription required to obtain full paper). The paper is

Ge, J., J. Qi, B. M. Lofgren, N. Moore, N. Torbick, and J. M. Olson (2007), Impacts of land use/cover classification accuracy on regional climate simulations, J. Geophys. Res., 112, D05107, doi:10.1029/2006JD007404.

The abstract reads,

“Land use/cover change has been recognized as a key component in global change. Various land cover data sets, including historically reconstructed, recently observed, and future projected, have been used in numerous climate modeling studies at regional to global scales. However, little attention has been paid to the effect of land cover classification accuracy on climate simulations, though accuracy assessment has become a routine procedure in land cover production community. In this study, we analyzed the behavior of simulated precipitation in the Regional Atmospheric Modeling System (RAMS) over a range of simulated classification accuracies over a 3 month period. This study found that land cover accuracy under 80% had a strong effect on precipitation especially when the land surface had a greater control of the atmosphere. This effect became stronger as the accuracy decreased. As shown in three follow-on experiments, the effect was further influenced by model parameterizations such as convection schemes and interior nudging, which can mitigate the strength of surface boundary forcings. In reality, land cover accuracy rarely obtains the commonly recommended 85% target. Its effect on climate simulations should therefore be considered, especially when historically reconstructed and future projected land covers are employed.”

An excerpt from the paper reads,

“Human activities are transforming the surface of the Earth at an accelerated pace. Such disturbance of the land can affect local, regional, and global climate by changing the energy balance on the Earth’s surface and the chemical composition of the atmosphere [Chase et al., 1999; Houghton et al., 1999; Pielke, 2001]. Over the past decades, land use/cover has been widely recognized as a critical factor mediating socioeconomic, political and cultural behavior and global climate change [International Geosphere-Biosphere Programme (IGBP), 1990; Lambin et al., 1999; Watson et al., 2000]. Numerous attempts have been made to understand past climate changes and to project potential future climate changes by incorporating reconstructed historical land cover changes and projected possible future land cover changes into numerical simulations [Xue, 1997; Pielke et al., 1999; Chase et al., 2000; DeFries et al., 2002; Taylor et al., 2002]. Recent studies have suggested that land use/cover change is a first-order climate effect at the global scale [Feddema et al., 2005].”

The 2007 IPCC Statement for Policymakers clearly chose to minimize the important role of land surface processes as part of the human influence on the climate system.

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Guest Weblog By Syun-Ichi Akasofu – Global Warming And The Little Ice Age

Dr. Syun-Ichi Akasofu has been the Director of the International Arctic Research Center of the University of Alaska Fairbanks since its establishment in 1998. He has been Professor of Geophysics since 1964. Dr. Akasofu has published more than 550 professional journal articles, authored and co-authored 10 books and has been the invited author of many encyclopedia articles. He has collaborated with numerous colleagues nationally and internationally, and has guided nine students to their Ph.D. degrees.

He is certainly well qualified scientifically to present his perspective on climate change. He has completed several articles on this subject; e.g.

Why has “global warmingâ€? become such a passionate subject?
– Let’s not lose our cool –

Is the Earth still recovering from the “Little Ice Ageâ€??
A possible cause of global warming

His contribution as a guest weblog follows:

Global Warming and the Little Ice Age

Many studies of the present global warming focus only on changes during the last 100 years or so, or after 1975 (based on satellite data). By extending records back for 100-200 years (however inaccurate the data may be, compared with satellite data) based on related publications, it has become clear that the present warming research is inadequate. This is because there has been a change of the temperature with an almost constant rate (about +0.5°C/100 years) from about 1800, or even much earlier, to the present. Since the increase began well before the rapid increase of CO2 in about 1940, this warming trend is likely to be a natural change.

One possible cause of the linear increase may be that the Earth is still recovering from the Little Ice Age. World glaciers and sea ice in the Arctic Ocean have been receding since 1800 or earlier; these are not just recent phenomena. It seems to me that most climate researchers are so caught up in the CO2 effect, the Little Ice Age has been all but forgotten.

In addition, multi-decadal oscillations were in a positive phase (~+0.1°C/10 years) during the last 30 years or so of the last century. These trends should be subtracted from the temperature data during the last 100 years.

Thus, there is a possibility that only a fraction of the present warming trend may be attributed to the greenhouse effect resulting from human activities. This conclusion is contrary to the IPCC (2007) Report, which states that “mostâ€? of the present warming (+0.7°C/100 years) is due to the greenhouse effect.

It is urgent that natural changes be correctly identified and removed accurately from the presently ongoing changes in order to find the contribution of the greenhouse effect. Some details are given at: http://www.iarc.uaf.edu/highlights/2007/akasofu_3_07/index.php

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More Background Information On Diagnosing Global Warming and Cooling

The value of using the ocean heat budget to diagnose the radiative imbalance at the top of the atmosphere was originally presented in the seminal paper

Ellis et al. 1978: The annual variation in the global heat balance of the Earth. J. Climate. 83, 1958-1962.

This was a motivation for the paper

Pielke Sr., R.A., 2003: Heat storage within the Earth system. Bull. Amer. Meteor. Soc., 84, 331-335.

In the Ellis et al paper on page 1961, the variation in the annual amplitude variation in the solar radiative forcing of 11.2 Watts per meter squared (due to the Earth’s elliptical orbit around the Sun) provides a perspective on global warming and cooling due to this “purely external driving mechanism”. While this heat imbalance sums to zero in an annual average, there clearly is global warming and cooling within each year. When all of the influences on the global heat budget are considered (see Figure 4), the variation across the year is on the order of 40 Watts per meter squared. This large variation in the value of global radiative imbalance within the year makes the accurate diagnosis of the multi-decadal trends in anthropogenic radiative forcing (the estimated 1.6 Watts per meter squared total net anthropogenic value of 1.6 Watts per meter squared) in Figure SPM-2 of the 2007 IPCC Statement for Policymakers a challenge.

This paper also confirms that dominate role of the oceans in the climate system response to the annual variation in solar insolation. They also express a particular interest in possible interannual variations from the average conditions reported in their paper. With the new ocean observing system (Argo), the plots of the estimated radiative imbalance should be prepared in near-real time on a monthly basis.

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A Fingerprint Of Human Effects On Weather And Climate: Literally! by Jos de Laat

A fingerprint of human effects on weather and climate: Literally!

This blog frequently reports about human fingerprints on weather and climate. It is a topic that also has my attention as a scientist (see for example here).

A few weeks ago there was a particular weather situation in my home country (the Netherlands) that nicely illustrates some effects of human activity on weather, and noted on the website from MeteoConsult, a Dutch commercial weather company. I noted this in an email to Roger, and he invited me to write a small guest-blog about this particular observations. So here we go.

A few weeks ago there was a particular weather situation in my home country (the Netherlands) that nicely illustrates some effects of human activity on weather, and noted on the website from MeteoConsult, a Dutch commercial weather company. I noted this in an email to Roger, and he invited me to write a small guest-blog about this particular observation. So here we go.

jos1.jpg

The weather here in the Netherlands during the last week or so has been stable, with high pressure dominating Western Europe. In this time of year that means quiet weather and cold nights with frequent formation of fog during night. During morning the fog starts to disappear because of solar insolation, and although this may take quite some time, most of the time it results in a sunny afternoon.

This was also the case on the morning of Sunday, 11 March 2007. The satellite image above (about 10:15 local time) shows that the western and central part of the country covered by fog and low-level clouds. Note that the east-west distance of this image is about 400 km. At many locations in the north and southeast it was already sunny with clear skies. What is remarkable about the image is the odd shape of the low-cloud area: it has fingers! The interesting question is: why did these fingers occur? As it turns out, these fingers are caused by the location of urban areas in the Netherlands.

On the second satellite picture below, the location of major urban areas in the western part of the country have been added. Clearly the cities of The Hague, Leiden, Haarlem, Amsterdam an Utrecht (close to where I live) are located at the most southern parts of the cloud-free bands, and there is just the slightest wind from the southwest (indicated by the red arrow). These are also the major urban regions in this area (look here for a geographical map of the Netherlands). A coincidence? Not likely.

jos2.jpg

During night, Earth’s surface cools radiatively. If sufficient moisture is present, the air near the surface may become saturated and fog or low clouds may start to appear. This results in a temperature inversion between the lowest atmosphere near the surface and layers above. The inversion layer prevents mixing with dryer air from above, and radiative cooling by the cloud (droplets) maintains cool surface temperatures. During daytime, when solar radiation increases and the atmosphere is heated, or when the air is more turbulent due to increased winds causing mixing with dryer layers from above, the clouds droplets start to evaporate and the clouds can disappear. If the radiative cooling outweighs the absorption of solar radiation, and mixing is insufficient, such cloud and fog areas can be very persistent, sometimes lasting throughout the day. However, in this particular case it appears that the break-up of the clouds was accelerated by the urban areas. But why?

There are two important reasons. First of all, urban areas add additional heat to the atmosphere, the so-called waste-heat effect. During this time of the year, with cold temperatures during night (close to freezing), people tend to warm their houses. In a densely populated area this can add quite some energy (heat) to the air. For example, the current amount of energy consumption averaged over the entire area of the Netherlands is nearly 4 W/m2 (National Institute for Statistics, CBS), by no means an insignificant number. For highly populated areas like cities, these values can even be much higher. And as the temperature of the air rises, clouds start to evaporate, and when the clouds disappear, solar radiation will reach the surface, further heating the air leading to evaporation of surrounding clouds.

A second process that plays a role is the presence of tall buildings in urban areas. These buildings distort the wind flow, causing enhanced turbulence (in meteorological terms: increased surface roughness) and more mixing. If the cloud/fog layer is sufficiently thin, and/or buildings are tall enough, the enhanced turbulence will mix in dryer air from above. This further accelerates the break-up of the fog and low clouds. This process is sometimes referred to as cloud-top entrainment instability.

The weather situation on this Sunday morning apparently was ideal to demonstrate the effect these processes can have on low clouds. Due to the particular location of urban areas, and with a little bit of fantasy, the fog area looks like the palm of a hand with outstretched fingers: an example of a true human fingerprint on weather and climate!

Jos de Laat, PhD, Royal Netherlands Meteorological Institute (KNMI).

With a special thanks for Casper Hootsen, Meteo Consult, the Netherlands, for noting this feature and writing an editorial about it on the Meteo Consult website, and Meteo Consult, for allowing the use of the editorial and satellite images. The satellite image is obtained from Meteosat MSG.

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New Paper On The Important Role Of Vegetation Within the Climate System

Jos de Laat of the Royal Dutch Meterological Institute (KNMI) has provided to us yet another very relevant new research paper. This article is on the role of vegetation processes within the climate center. The paper is

Effects of Land Surface-Vegetation on the Boreal Summer Surface Climate of a GCM, by Alessandri et al., Journal of Climate, 15 January 2007, doi: 10.1175/JCLI3983.1

The abstract reads

A land surface model (LSM) has been included in the ECMWF Hamburg version 4 (ECHAM4) atmospheric general circulation model (AGCM). The LSM is an early version of the Organizing Carbon and Hydrology in Dynamic Ecosystems (ORCHIDEE) and it replaces the simple land surface scheme previously included in ECHAM4. The purpose of this paper is to document how a more exhaustive consideration of the land surface–vegetation processes affects the simulated boreal summer surface climate.

To investigate the impacts on the simulated climate, different sets of Atmospheric Model Intercomparison Project (AMIP)-type simulations have been performed with ECHAM4 alone and with the AGCM coupled with ORCHIDEE. Furthermore, to assess the effects of the increase in horizontal resolution the coupling of ECHAM4 with the LSM has been implemented at different horizontal resolutions.

The analysis reveals that the LSM has large effects on the simulated boreal summer surface climate of the atmospheric model. Considerable impacts are found in the surface energy balance due to changes in the surface latent heat fluxes over tropical and midlatitude areas covered with vegetation. Rainfall and atmospheric circulation are substantially affected by these changes. In particular, increased precipitation is found over evergreen and summergreen vegetated areas. Because of the socioeconomical relevance, particular attention has been devoted to the Indian summer monsoon (ISM) region. The results of this study indicate that precipitation over the Indian subcontinent is better simulated with the coupled ECHAM4–ORCHIDEE model compared to the atmospheric model alone.”

Important excerpts from the paper reads,

The coupling with ORCHIDEE has been shown to have a considerable impact on the boreal summer surface air temperature simulated by ECHAM4. A warmer 2-m temperature (T2m) is found over large continental areas in middle and high latitudes of the Northern Hemisphere. A particularly strong T2m increase is found over eastern Asia. The warmer temperature over these areas also leads to increased land– sea contrast in sea level pressure (SLP), which, in turn, induces changes in the atmospheric circulation.

“Land surface–vegetation processes have considerable biophysical effects on climate and, as evidenced in this study, their inclusion in AGCMs is a major task in order to improve our skill in surface climate simulation. In this work, a prescribed vegetation representation has been used, and the seasonal cycle of the vegetation cover is simply computed as a function of soil temperature. This kind of approach leads to an unrealistically small interannual variability in vegetation cover and, as shown in this work, a poor representation of the seasonal cycle in semiarid tropical regions. In particular, this latter shortcoming has been shown to contribute to the precipitation bias found in EchOrc over the Sahel. By virtue of these considerations, a further improvement in the simulated surface climate is expected from the inclusion in the EchOrc AGCM of a fully interactive dynamical global vegetation model, which is suitable to reproduce in a more realistic way the interannual and seasonal variations in the vegetation characteristics.”

This paper further documents the major role of vegetation on the surface air temperature (an issue which was not assessed at all in the CCSP report Temperature Trends in the Lower Atmosphere: Steps for Understanding and Reconciling Differences as it should have (see), as well as the importance of vegetation processes in affecting regional climate patterns as recognized in the 2005 NRC report Radiative forcing of climate change: Expanding the concept and addressing uncertainties.

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An Excellent Summary Analysis Of Extreme Temperatures In the United States

Record high and low temperature records are of particular interest due to the major impacts they have on society and the environment. Bruce Hall has completed an analysis of record temperatures on his website Hall of Record that is a very valuable resource for this climate metric. Similar analyses for elsewhere in the world should be a high priority.

His excellent weblogs on this subject can obtained from

U.S. Extreme Temperatures Update

Extreme High Temperatures – State Details (1884-2004)

Global Warming Without New High Temperature Extremes

Extreme Temperatures As A Measure Of Global Warming

Extreme Temperatures – Where’s the Global Warming?

See also the informative comments by Dr. Scott Robeson of Indiana University with respect to the weblogs.

As noted on his weblog (see), the graphs can be viewed at Climate Science at

http://www.climatesci.org/comment-uploads/us_extreme_temp.xls Click on the “Temperature Database” tab at the bottom,

http://www.climatesci.org/comment-uploads/record_low_temp.jpg

http://www.climatesci.org/comment-uploads/record_high_temp.jpg

The importance of documenting extreme temperatures was discussed on Climate Science;see

EOS Paper On The Hottest Spots on Earth Illustrates The Major Role of Landscape on Surface Temperatures

We also invesitgate this issue for eastern Colorado in the papers,

Pielke Sr., R.A., T. Stohlgren, W. Parton, J. Moeny, N. Doesken, L. Schell, and K. Redmond, 2000: Spatial representativeness of temperature measurements from a single site. Bull. Amer. Meteor. Soc., 81, 826-830.

Pielke Sr., R.A., T. Stohlgren, L. Schell, W. Parton, N. Doesken, K. Redmond, J. Moeny, T. McKee, and T.G.F. Kittel, 2002: Problems in evaluating regional and local trends in temperature: An example from eastern Colorado, USA. Int. J. Climatol., 22, 421-434.

It is clear the trends in record setting temperatures in the United States are not consistent with one would expect with an increase in the mean temperature, and, iny case need to be assessed as a very important climate metric.

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