Monthly Archives: April 2009

New Paper “Influence Of Modern Land Cover On The Climate Of The United States” By N. S. Diffenbaugh 2009

There is a new paper that provides yet another example that land cover change is  first order climate forcing. [ and thanks to Souleymane Fall for alerting us to this paper!].

The paper is

Diffenbaugh, N. S., 2009:Influence of modern land cover on the climate of the United States. Climate Dynamics. DOI 10.1007/s00382-009-0566-z (in press).
The abstract reads

“I have used a high-resolution nested climate modeling system to test the sensitivity of regional and local climate to the modern non-urban land cover distribution of the continental United States. The dominant climate response is cooling of surface air temperatures, particularly during the warm-season. Areas of statistically significant cooling include areas of the Great Plains where crop/mixed farming has replaced short grass, areas of the Midwest and southern Texas where crop/mixed farming has replaced interrupted forest, and areas of the western United States containing irrigated crops. This statistically significant warm-season cooling is driven by changes in both surface moisture balance and surface albedo, with changes in surface moisture balance dominating in the Great Plains and western United States, changes in surface albedo dominating in the Midwest, and both effects contributing to warm-season cooling over southern Texas. The simulated changes in surface moisture and energy fluxes also influence the warm-season atmospheric dynamics, creating greater moisture availability in the lower atmosphere and enhanced uplift aloft, consistent with the enhanced warmseason precipitation seen in the simulation with modern land cover. The local and regional climate response is of a similar magnitude to that projected for future greenhouse gas concentrations, suggesting that the climatic effects of land cover change should be carefully considered when crafting policies for regulating land use and for managing anthropogenic forcing of the climate system.”

The conclusion has the text

“These results have important implications for future climate, energy, and land use policies. For instance, future conversion from crop to other land types could cause warming (particularly through urbanization (Kueppers et al. 2007)) and afforestation for carbon sequestration (e.g., Diffenbaugh 2005a; Jackson et al. 2008), while future expansion of crop area could cause cooling (particularly through expansion into marginal areas that require substantial irrigation). Further, in addition to direct influences on climate, the presence of agriculture could suppress regional and local warming at high greenhouse gas levels (Diffenbaugh et al. 2005; White et al. 2006), meaning that there could be secondary climatic effects of transitioning crops to forests as greenhouse gas concentrations continue to rise. The results presented here therefore suggest that the climatic effects of land cover change should be carefully considered when crafting policies for regulating land use and for managing anthropogenic forcing of the climate system.”

This study reinforces the 2005 National Research Council report on the need to broaden the assessment of the role of humans within the climate system, beyond that due to the emissions of well-mixed greenhouse gases. This scientifically robust perspective was ignored in the EPA report last week of the plan to regulate CO2 and several other gases due to their role as climate forcings.

The author could also expand his analysis to assess the heat content (moist enthalpy) changes that result from these land conversions (e.g. see and see). The change to agriculture, for example, would generally result in added water vapor and a darker surface albedo, both of which would elevate the moist enthalpy. Since moist enthalpy (in units of Joules per kilogram of air), rather than dry bulb temperature by itself, is the actual metric for heat, this would provide additional insight into the role of landscape change on the climate.

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Filed under Climate Change Forcings & Feedbacks, Research Papers

Comment On “Debate Over Climate Risks – Natural or Not” On Dot Earth

There is an interesting discussion on going at Andy Revkin’s weglob Dot Earth on the topic Debate Over Climate Risks – Natural or Not,  which invites responses to the statement,

“One clear-cut lesson [of this study] seems to be that human-driven warming, for this part of Africa, could be seen as a sideshow given the normal extremes. Tell me why that thought is misplaced if you feel it is.”

 This subject was initiated by a Science article by Shanahan et al  and subsequent news item on April 16 2009 by Andy Revkin which includes the text

“For at least 3,000 years, a regular drumbeat of potent droughts, far longer and more severe than any experienced recently, have seared a belt of sub-Saharan Africa that is now home to tens of millions of the world’s poorest people, climate researchers reported in a new study.

That sobering finding, published in the April 17th issue of Science magazine emerged from the first study of year-by-year climate conditions in the region over the millenniums, based on layered mud and dead trees in a crater lake in Ghana. “

The abstract of the Science article by Shanahan et al reads

” Although persistent drought in West Africa is well documented from the instrumental record and has been primarily attributed to changing Atlantic sea surface temperatures, little is known about the length, severity, and origin of drought before the 20th century. We combined geomorphic, isotopic, and geochemical evidence from the sediments of Lake Bosumtwi, Ghana, to reconstruct natural variability in the African monsoon over the past three millennia. We find that intervals of severe drought lasting for periods ranging from decades to centuries are characteristic of the monsoon and are linked to natural variations in Atlantic temperatures. Thus the severe drought of recent decades is not anomalous in the context of the past three millennia, indicating that the monsoon is capable of longer and more severe future droughts.”

Climate Science and our research papers have emphasized the large natural variations of climate that have occurred in the paleo-climate record and that these variations dwarf anything we have experienced in the instrumental record.

For example, in

Rial, J., R.A. Pielke Sr., M. Beniston, M. Claussen, J. Canadell, P. Cox, H. Held, N. de Noblet-Ducoudre, R. Prinn, J. Reynolds, and J.D. Salas, 2004: Nonlinearities, feedbacks and critical thresholds within the Earth’s climate system. Climatic Change, 65, 11-38,

our abstract reads

“The Earth’s climate system is highly nonlinear: inputs and outputs are not proportional, change is often episodic and abrupt, rather than slow and gradual, and multiple equilibria are the norm. While this is widely accepted, there is a relatively poor understanding of the different types of nonlinearities, how they manifest under various conditions, and whether they reflect a climate system driven by astronomical forcings, by internal feedbacks, or by a combination of both. In this paper, after a brief tutorial on the basics of climate nonlinearity, we provide a number of illustrative examples and highlight key mechanisms that give rise to nonlinear behavior, address scale and methodological issues, suggest a robust alternative to prediction that is based on using integrated assessments within the framework of vulnerability studies and, lastly, recommend a number of research priorities and the establishment of education programs in Earth Systems Science. It is imperative that the Earth’s climate system research community embraces this nonlinear paradigm if we are to move forward in the assessment of the human influence on climate.”

In an article specifically with respect to drought,

Pielke Sr., R.A., 2008: Global climate models – Many contributing influences. Citizen’s Guide to Colorado Climate Change, Colorado Climate Foundation for Water Education, pp. 28-29,

I wrote

“A vulnerability perspective, focused on regional and local societal and environmental resources, is a more inclusive, useful and scientifically robust framework to use with policymakers. In contrast to the limited range of possible future risks by current climate models, the vulnerability framework permits the evaluation of the entire spectrum of risks to the water resources associated with all social and environmental threats, including climate variability and change.”

Thus, regardless of the role humans play within the climate system (and it is much more than due to carbon dioxide increases; see), adaptation plans to deal with climate variations, beyond what occurred in the historical record, should be a priority.


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Filed under Climate Science Reporting, Vulnerability Paradigm

Another Example Of An Environmental Tradeoff – Reduced CO2 Emissions And Lower Fuel Cost Versus Personal Safety

Climate Science has often blogged on the need to assess the entire spectrum of effects when a particular environmental (or other) regulation is implemented (e.g. see and see).

In the April 14 2009 news there is a well written article by Ken Thomas of the AP which provides another example of the multi-faceted effects of particular decision with respect to the environment.

In this case, the issue is the benefit to the environment of reduced emissions of carbon dioxide and lower fueling costs from a  smaller passenger vehicle, versus the risk to the personal safety of you and your family.

The article is “Small cars get poor marks in collision tests” and reads

WASHINGTON — Micro cars can give motorists top-notch fuel efficiency at a competitive price, but the insurance industry says they don’t fare too well in collisions with larger vehicles.

In crash tests released Tuesday, the Insurance Institute for Highway Safety found that drivers of 2009 versions of the Smart “fortwo,” Honda Fit and Toyota Yaris could face significant leg and head injuries in severe front-end crashes with larger, mid-size vehicles.

“There are good reasons people buy mini cars. They’re more affordable, and they use less gas. But the safety trade-offs are clear from our new tests,” said Adrian Lund, the institute’s president.

Automakers who manufacture the small cars said the tests simulated a high-speed crash that rarely happens on the road. They also said the tests rehashed past insurance industry arguments against tougher fuel efficiency requirements. The institute has raised questions about whether stricter gas mileage rules, which are being developed by the government, might lead to smaller, lighter vehicles that could be less safe.

“If you were to take that argument to the nth degree, we should all be driving 18-wheelers. And the trend in society today is just the opposite,” said Dave Schembri, president of Smart USA.

Sales of small cars soared when gas prices topped $4 per gallon last year but have fallen off as gasoline has retreated to about $2 a gallon and the economic downturn has slowed car sales. The small cars are affordable — prices of the three cars tested range from about $12,000 to $18,000 — and typically achieve 30 miles per gallon or more.

The tests involved head-on crashes between the fortwo and a 2009 Mercedes C Class, the Fit and a 2009 Honda Accord and the Yaris and the 2009 Toyota Camry. The tests were conducted at 40 miles per hour, representing a severe crash.

In the fortwo collision, the institute said the Smart, which weighs 1,808 lbs, went airborne and turned around 450 degrees after striking the C Class, which weighs nearly twice as much. There was extensive damage to the fortwo’s interior and the Smart driver could have faced extensive injuries to the head and legs. There was little damage to the front seat area of the C Class.

Schembri said the test simulated a “rare and extreme scenario” and noted that the fortwo had received solid ratings from the government’s crash test program. The fortwo has received top scores from the Insurance Institute in front-end and side crash tests against comparably sized vehicles but in the front-end tests against the C Class, the institute gave the mini car poor marks.

In the Fit’s test, the dummy’s head struck the steering wheel through the air bag and showed a high risk of leg injuries. In the vehicle-to-vehicle test, the Fit was rated poor while the Accord’s structure held up well.

Honda spokesman Todd Mittleman said the tests involved “unusual and extreme conditions” and noted that all 2009 Honda vehicles had received top scores from the Insurance Institute.

In the Yaris test, the institute said the mini car sustained damage to the door and front passenger area. The driver dummy showed signs of head injuries, a deep gash on the right knee and extensive forces to the neck and right leg.

The Yaris has received good ratings in past front and side testing but received a poor rating in the crash with the Camry. Toyota spokesman John Hanson said the car-to-car test had little relevance to consumers because of its severity.

“It’s fairly obvious that they have an agenda here with regard to how smaller cars are going to be entering the North American market in larger numbers,” Hanson said.”

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Filed under Climate Science Reporting, Vulnerability Paradigm

“Air Temperature Change Due To Human Activities In Taiwan For The Past Century” By Lai and Cheng 2009

 There is another excellent paper which documents the significant role of local human activites on the long termperature trends, as well as challenges the development of grid averaged temperatures using the observed large heterogeniety of the surface temperature observations [Thanks to Geoff Smith for altering us to this paper!].

The paper is

Lai, L.-W., and W.-L.Cheng 2009: Air temperature change due to human activities in Taiwan for the past century. Int. J. Climatology, 10.1002/joc.1898.

The abstract reads

“The purpose of this study was to statistically examine air temperature change and to analyse the anthropogenic factors potentially influencing air temperature changes in Taiwan for the period 1897-2005 using homogenized temperature measurement time series. In this study, the standard normal homogeneity test was used to attain homogeneity of all air temperature series. To analyse air temperature data from 1897 to 2005, a time-series regression model and a product-moment correlation were used. The annual mean maximum temperatures (Tmax), annual mean minimum temperatures (Tmin) and the number of days in which the air temperature 30°C increased significantly in most regions in Taiwan, and the rate of increase for Tmin was higher than that of Tmax. In other words, in the past century the night temperatures have become higher and the period of hot days in Taiwan have become longer. However, over the past century and before 1962, the trend of Tmax in central Taiwan (i.e. Jihyuehtan and Taichung) decreased significantly, which is inconsistent with greenhouse gas warming and general warming observed in other sites in Taiwan. Furthermore, during the economic growth experienced between 1962 and 2005, the rates of increase for Tmax and Tmin in major cities with similar climate conditions (i.e. Tainan and Kaohsiung) were significantly different, as were the correlation coefficients between temperature changes and the number of various economic sectors in the cities. The results of these statistical analyses suggest that human activities strongly affected air temperature changes in these urban areas. The obvious lack of spatial homogeneity indicates that various non-greenhouse gas processes have played roles in climate change in Taiwan, and these factors must be considered when analysing long-term air temperature variations. Caution should be exercised when using grid data to assess temperature trends at the grid-box level.”

The conclusions include the text

 “In conclusion, the results from this study strongly suggest that, during Taiwan’s ‘economic boom period’, its rapid expansion in terms of population and economic activities influenced air temperature changes directly (i.e. emitting GHGs and generating anthropogenic heating) and indirectly (i.e. changing the urban landscape, such as the depth of street canyons; the H/W ratio; proximity to the sea; vegetation space; SVF and heat capacity).”

Their statement that

The obvious lack of spatial homogeneity indicates that various non-greenhouse gas processes have played roles in climate change in Taiwan, and these factors must be considered when analysing long-term air temperature variations. Caution should be exercised when using grid data to assess temperature trends at the grid-box level”

raises questions about the robustness of the homogenization of the surface temperature trend record, as we also raised in our paper

Pielke Sr., R.A. J. Nielsen-Gammon, C. Davey, J. Angel, O. Bliss, N. Doesken, M. Cai., S.  Fall, D. Niyogi, K. Gallo, R. Hale, K.G. Hubbard, X. Lin, H. Li, and S. Raman, 2007: Documentation of uncertainties and biases associated with surface temperature measurement sites for climate change assessment. Bull. Amer. Meteor. Soc., 88:6, 913-928.

where we stated in our abstract that

“The use of temperature data from poorly sited stations can lead to a false sense of confidence in the robustness of multidecadal surface air temperature trend assessments.” 

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Filed under Climate Change Metrics, Research Papers

A New Paper “An Analytical Framework For Estimating The Urban Effect On Climate” By Lamptey 2009

There is an excellent new paper that further exmines the role of urban areas in climate. [Thanks to Geoff Smith for altering us to it!].  The article is

Lamptey, B., 2009: An analytical framework for estimating the urban effect on climate. Int. J. Climatology, DOI: 10.1002/joc.1873

The abstract reads

 “The surface energy budget has been used to illustrate the influence of urban landscape on both global and regional climate. This was done using empirical as well as remotely sensed data of components of the surface energy equation. At the global scale, the urban land cover has the least impact on the sensible and latent heat fluxes compared to the other land cover types. Replacing the urban land cover with vegetation did not result in a significant change to the proportionate values of the turbulent fluxes originally due to vegetation. The least impact of current urbanization on the global climate in terms of radiation and surface fluxes is because the urban land cover has the smallest fraction of all the land cover types. The relative importance of the urban landscape at the regional scale was illustrated using the example of Chester County and surroundings near Philadelphia, Pennsylvania, in the USA. The urban effect becomes more important as the fraction of urban land cover to the total increases. This is illustrated by computing turbulent fluxes for 1987, 1988, 1991, 1993 and 1996 over the Chester County area. Urbanization in Chester County and surrounding areas increased from 11% in 1987 to 19% in 1996. In 1996, urban land cover produced the largest proportionate sensible (21.4 Wm-2) and latent (14.2 Wm-2) heat fluxes during winter. During the 1996 summer, urban and vegetation land cover produced the largest proportionate sensible heat (59.2 Wm-2) while urban land cover produced the second largest proportionate latent heat flux (39.5 Wm-2). The implications of this simple analytical study point to the need to account for the urban landscape particularly in regional studies.”

The conclusions include the text

 “It has been shown from an analytical approach that the impact of urbanization is important at the regional scale. The impact of urban land cover becomes relatively more important as the fraction of urban land cover increases.”

Among its implications, this study provides further evidence as to the role of the urban landscape on long term trends in surface temperatures.  As documented in his paper,  urbanization changes over time (which is relatively gradual). Thus, surface air temperature increases in these areas could be incorrectly attributed to “global warming” when in reality they are due to this landscape change.

The conclusion of the significant role of landscape change on surface temperature trends which is obtained from the Lamprey paper bolsters the conclusions that we reached in

Pielke Sr., R.A., C. Davey, D. Niyogi, S. Fall, J. Steinweg-Woods, K. Hubbard, X. Lin, M. Cai, Y.-K. Lim, H. Li, J. Nielsen-Gammon, K. Gallo, R. Hale, R. Mahmood, S. Foster, R.T. McNider, and P. Blanken, 2007: Unresolved issues with the assessment of multi-decadal global land surface temperature trends. J. Geophys. Res., 112, D24S08, doi:10.1029/2006JD008229.


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Filed under Climate Change Metrics, Research Papers

Climate Science Comment On The April 11 2009 Guest Weblog By Dr. James E. Hansen

Dr. Jim Hansen of GISS wrote a guest weblog on April 11 2009, and Climate Science will follow up with a few comments here. First, his willingness to engage in a constructive discussion of the science issues should be a message to other climate scientists, who have elected not to engage in such discussions. Thanks again to Jim for doing this.

With respect to the science, these are my comments:

  • We both agree that land use change is a first-order climate forcing on the local scale;
  • We both agree that in terms of the global average radiative imbalance, that land use change, so far, has been less than that caused by the anthropogenic addition of the well-mixed greenhouse gases and aerosols;
  • We disagree, however, on what is the role of land use change in altering global climate patterns. Our research (e.g. see), and that of others (e.g. see) demonstrates that atmospheric circulations are significantly altered on the hemispheric and global scale due to human land management practices. These changes will, of course, result in long term effects of the frequency of such societally important climate events as droughts, tropical cyclones, and floods.

With respect to the last bullet, Climate Science urges the broadening of the climate metrics in order to more appropriately assess the human role in altering climate patterns. Our research (e.g. see) has proposed the assessment of the change using the spatial gradient of radiative heating (and other diabatic heating) due to all climate forcings, as one climate metric to complete such an evaluation.  We have found in the tropics and subtropics, for example, (see) that the large spatial heterogeneity of aerosols has a 60X greater influence on the gradient of diabatic heating than is found with the spatial heterogeneity of the well-mixed greenhouse gases.

Existing research indicates that the multi-decadal changes in this gradient produce a greater influence on the climate change that society experiences than is communicated by a global average surface temperature trend, or any other global average.

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“Limits On The Space Launch Market Related To Stratospheric Ozone Depletion” By Ross et al. 2009

There is a new paper (which one of authors, Professor Darin Toohey, effectively weblogged on last week; see). The article is

Ross, M., D. Toohey, M. Peinemann, and P. Ross, 2009: Limits on the Space Launch Market Related to Stratospheric Ozone Depletion Astropolitics, 7, 50-82, doi:10.1080/14777620902768867.

and which directly relates to the issue of geoengineering as discussed, for example, in a recent interview by John Holdren who is President Obama’s science advisor (see), and weblogged on by Professor Toohey.

The abstract of the paper reads

 “Solid rocket motors (SRMs) and liquid rocket engines (LREs) deplete the global ozone layer in various capacities. We estimate global ozone depletion from rockets as a function of payload launch rate and relative mix of SRM and LRE rocket emissions. Currently, global rocket launches deplete the ozone layer ∼0.03%, an insignificant fraction of the depletion caused by other ozone depletion substances (ODSs). As the space industry grows and ODSs fade from the stratosphere, ozone depletion from rockets could become significant. This raises the possibility of regulation of space launch systems in the name of ozone protection. Large uncertainties in our understanding of ozone loss caused by rocket engines leave open the possibility that launch systems might be limited to as little as several tens of kilotons per year, comparable to the launch requirements of proposed space systems such as spaceplanes, space solar power, and space reflectors to mitigate climate change. The potential for limitations on launch systems due to idiosyncratic regulation to protect the ozone layer present a risk to space industrial development. The risk is particularly acute with regard to the economic rationale to develop low-cost, high flight rate launch systems.”

with its press releases at:

Clearly, as reported on Climate Science, any attempt for a solution  to an environmental concern which is considered too narrowly (e.g. see also with respect to biofuels), can result in serious unanticipated consequences. For additional discussion on Climate Science with respect to geoengineering; see

Comments On The Physics Today Article “Will Desperate Climates Call for Desperate Geoengineering Measures?” by Barbara Goss Levi.



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Filed under Climate Change Forcings & Feedbacks, Climate Change Regulations, Research Papers