Monthly Archives: July 2009

The Importance Of Regonal Climate Forcings

This post provides a brief overview of why regional climate forcings are first order in terms of affecting atmospheric circulation patterns which are the reason for such weather events as droughts, floods, tropical cyclones and so forth.  A global average radiative forcing, such as emphasized in the 2007 IPCC report, fails to capture these forcings, and indeed, obscures their significance.

Examples include (with excerpts from the papers)

1. Feddema et al. 2005: The importance of land-cover change in simulating future climates., 310, 1674-1678.

“Although land-cover effects are regional and tend to offset with respect to global average temperatures, they can significantly alter regional climate outcomes associated with global warming. Beyond local impacts, tropical land-cover change can potentially affect extratropical climates and nearby ocean conditions through atmospheric teleconnections.”

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

“Recent studies suggest that changes in the surface energy budgets resulting from land surface change can have a profound influence on the Earth’s climate…………….”

“Having observed that local and regional changes in climate may be as important as changes in the global mean climate, we suggest that attention be given to devising a regional climate change potential (RCCP) to encapsulate the effect that specific human actions have on the redistribution of energy within the Earth’s climate system.”

3. Pitman, A.J., N. de Noblet-Ducoudré, F.T. Cruz, E.L. Davin, G.B. Bonan, V. Brovkin, M. Claussen, C. Delire, L. Ganzeveld, V. Gayler, B.J.J.M. van den Hurk, P.J. Lawrence, M.K. van der Molen, C. Müller, C.H. Reick, S.I. Seneviratne, B. J. Strengers, and A. Voldoire, 2009: Uncertainties in climate responses to past land cover change: first results from the LUCID intercomparison study, Geophys. Res. Lett., doi:10.1029/2009GL039076, in press. [“Land-Use and Climate, IDentification of robust impacts” (LUCID)] (see)

“Seven climate models were used to explore the biogeophysical impacts of human induced land cover change (LCC) at regional and global scales. The imposed LCC led to statistically significant decreases in the northern hemisphere summer latent heat flux in three models, and increases in three models. Five models simulated statistically significant cooling in summer in near-surface temperature over regions of LCC and one simulated warming.”

4. McAlpine, C.A., J. Syktus, J.G. Ryan, R.C. Deo, G.M. McKeon, H.A. McGowan, and S.R. Phinn, 2009:A continent under stress: interactions, feedbacks and risks associated with impact of modified land cover on Australia’s Climate. Global Change Biology, in press. doi: 10.1111/j.1365-2486.2009.01939.x (see)

“The consequences of ignoring the effect of LUCC on current and future droughts in Australia could have catastrophic consequences for the nation’s environment, economy and communities”

5. Takata, K., K. Saito, and T. Yasunari, 2009: Changes in the Asian Monsoon Climate During 1700-1850 Induced by Pre-Industrial Cultivation. PNAS,(in press). (see)

“Pre-industrial changes in the Asian summer monsoon climate from the 1700s to the 1850s were estimated with an Atmospheric General Circulation Model (AGCM) using historical global land cover/use change data reconstructed for the last 300 years. Extended cultivation resulted in a decrease in monsoon rainfall over the Indian subcontinent and southeastern China, and an associated weakening of the Asian summer monsoon circulation. The precipitation decrease in India was marked, and was consistent with the observational changes derived from examining the Himalayan ice-cores for the concurrent period. Between the 1700s and the 1850s, the anthropogenic increases in greenhouse gases and aerosols were still minor; also, no long-term trends in natural climate variations, such as those caused by the ocean, solar activity, or volcanoes, were reported. Thus, we propose that the land cover/use change was the major source of disturbances to the climate during that period.”

6.   2002 Science paper entitled “Climate Effects of Black Carbon Aerosols in China and India” (subscription required) by S. Menon, J. Hansen, and L. Nazarenko and Y. Luo. (see)

“In recent decades, there has been a tendency toward increased summerfloods in south China, increased drought in north China, and moderate cooling in China and India while most of the world has been warming. We used a global climate model to investigate possible aerosol contributions to these trends. We found precipitation and temperature changes in the model that were comparable to those observed if the aerosols included a large proportion of absorbing black carbon (”soot”), similar to observed amounts. Absorbing aerosols heat the air, alter regional atmospheric stability and vertical motions, and affect the large-scale circulation and hydrologic cycle with significant regional climate effects. ”

7. Matsui, T., and R.A. Pielke Sr., 2006: Measurement-based estimation of the spatial gradient of aerosol radiative forcing. Geophys. Res. Letts., 33, L11813, doi:10.1029/2006GL025974.

“This paper diagnoses the spatial mean and the spatial gradient of the aerosol radiative forcing in comparison with those of well-mixed green-house gases (GHG). Unlike GHG, aerosols have much greater spatial heterogeneity in their radiative forcing. The heterogeneous diabatic heating can modulate the gradient in horizontal pressure field and atmospheric circulations, thus altering the regional climate.”

These example illustrate why the IPCC assessments must be broadened to include the diversity of heterogenous human climate forcings.

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Announcement Of American Geophysical Union Sessions On Natural Hazards At The December 2009 Annual Meeting

As emphasized on my weblog (e.g.see), we need to focus more on reducing societal and environmental vulnerability to environmental variability and change of all types, including, but not limited to climate variability and change. The American Geophysical Union is having a number of important sessions on hazards at the December meeting. The list of theses sessions is available at AGU 2009 [thanks to Ilia Zaliapin for providing us this information!] . The search for all sessions at the AGU meeting is also available (see).





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Madhav Khandekar Has Reviewed The Book “The Asian Monsoon: Causes, History & Effects By Peter D Clift And R Allan Plumb

The following is a review of a book on the Asian monsoon by Madhav Khandekar. Since my weblog has recently posted an announcement on a very important new paper on this subject (see) and we have also published on the Asian monsoon (e.g. see), I wanted to alert readers of the availability of this publication, and the very insightful review by Madhav.


Book Reviewed by Madhav Khandekar: Madhav Khandekar is a former research scientist from Environment Canada. He is presently on the editorial board of the international Journal Natural Hazards and was an Expert Reviewer for the 2007 IPCC climate change documents.

View Inside  


The Asian Monsoon – Causes, History and Effects by Peter D. Clift, University of Aberdeen and R. Alan Plumb, Massachusetts Institute of Technology, Cambridge University Press, 2008.

“The Asian monsoon is one of the most dramatic climatic phenomena on earth today, with far-reaching environmental and societal effects. Almost two thirds of humanity live within regions influenced by the  onsoon. Monsoon strength and variability have been and will continue to be crucial to the past and future prosperity of the region”.

 The preface of this book opens with some dramatic phrases about the Asian monsoon, which indeed impacts two thirds of the world’s humanity today, or about 4 billion people living in Asia from Pakistan in the northwest to Indonesia in the southeast and from the Maldive Islands in the southwest to China in the northeast. The Asian monsoon is the largest seasonal abnormality of the global climate system and exerts a significant impact on the earth’s climate system. In the context of present debate on global warming and  limate change, it is imperative that a comprehensive understanding of this fascinating and complex climate system must be developed before any meaningful assessment of present and future climate change can be made.

The Asian Monsoon presents a primarily paleo-climatic perspective on the Asian monsoon. The authors, Clift & Plumb (both affiliated with the Massachusetts Institute of Technology in USA), are experts in the area of monsoon climate and have presented a comprehensive account on the evolution and controls of the Asian monsoon over tectonic and orbital time-scales in the first five chapters. The authors have analyzed a large number of research publications on a variety of paleo-oceanographic data to document monsoon evolution and variability over timescales from several tens of million years BP (Before Present) to just a few thousand to a few hundred years BP. The final chapter of the book deals with the late Holocene (about 5000 y BP) monsoon and human society, which provides an interesting account of social and cultural development of human societies over Asia with particular reference to the Indus Valley civilization (~7000 y BP) over the Indian subcontinent and the Dadiwan culture (~7500 y BP) from the Yellow River valley in China. This chapter also discusses monsoon development over the last 1000 years with reference to monsoon variability and political development and changes, especially over India. The book ends with a brief discussion on future evolution of the monsoon in the context of present debate on climate change, this discussion being derived primarily from the 2001 climate change documents prepared by the IPCC (Intergovernmental Panel on Climate Change).

The first chapter of the book presents the meteorology of the monsoons, with relevant schematics and discussions on the sub-tropical jet stream, the Hadley Cell inrelation to the tropics, the ITCZ (Inter-tropical Convergence Zone) and the impact of the Indian Ocean on monsoon circulation. It was puzzling and disappointing to find no reference to the Tropical Easterly Jet (TEJ), an important and persistent jet stream over the Peninsular India (with peak winds of up to 100 knots at about 100 hPa) which owes its existence to the reversal of north-south temperature gradient over south Asia due to presence of the Tibetan Plateau and its significant warming during summer months in relation to the ‘cooler’ Indian Ocean in the south. It is this TEJ which makes the Asian and in particular the Indian monsoon complex and a fascinating research topic today.

The next two chapters discus the controls and evolution of the Asian monsoon on tectonic time-scale, from several tens of M y BP to a few hundred years BP. Chapter 2 discusses the importance of the Tibetan Plateau together with the Himalayan mountains (highest mountain chains in the world) on the strength and intensity of monsoons. The Tibetan Plateau is now believed to have evolved at around 45 to 50 M y BP and its importance in controlling the monsoon and rainfall intensity over India, central Asia and over Loess Plateau (in central China) is discussed at length. Once again, it is disappointing to see a complete absence of any reference to TEJ, which has been shown (in many studies in the 1960s by researchers in the India Meteorological Department) to exert an important control on the monsoon circulation and intensity, over the Indian subcontinent and also over parts of northern Africa where the TEJ extends during summer months. In chapter 3, the evolution of Asian monsoon over glacial and interglacial intervals is presented. A large amount of data from ocean floors (e.g., Arabian Sea sediments), weathering histories in the Himalayas and eolian dust records are analyzed to establish monsoon variability over several M years and in particular the strengthening of the summer monsoon about 8 M y BP due to the Tibetan Plateau. In chapter 4 the evolution of monsoon over orbital time-scales (from a few thousand to hundred thousand years or more) is investigated using a variety of data, e.g. cave data, lake records, eolian data, etc. The earth’s orbit exhibits three types of long-term variations, namely eccentricity (~100,000 y), obliquity (~41000 y) and precession (~21000 y) and this also reflects in monsoon strength which varies on the 21, 40 and 100 thousand year time-scales that control periods of glacial advances and retreats. Chapter 5 discusses the erosional impact of the Asian monsoon and how this may have impacted the tectonics of the Asian mountain ranges. The chapter concludes that the monsoon circulation and intensity had a powerful influence on the erosion and weathering of Asia over long and short geological times during the Cenozoic (~70 M y ) and this erosional impact has resulted in an important coupling between the climate and the tectonic evolution of the mountains.

The last chapter discusses the late Holocene monsoon variability and how this has shaped the human society and culture over Asia. The authors employ records derived from ice cores, spelothems, lakes and peat bogs to assess monsoon strengths since about 8000 y BP to the present. The monsoon strengthening, following the very cold period of Younger Dryas (~ 11000 y BP) allowed vegetation to spread and diversify and this, according to the authors, may have led to the development of the Harappan and Mohenjodaro culture between 9000 to 6000 y BP. Extensive remains of this culture are found in the northwest parts of India (which is now part of Pakistan) along the Indus River valley and in particular along the River Saraswati, referred to many times in the Hindu scriptures, The Rig Veda, written about 6000 y BP. The Saraswati River, which was a major river then, has all but disappeared today, most certainly due to drying of the monsoonal climate after 4200 y BP. The drying of Asian monsoon after 5000 y BP is also inferred from sediment records in northeast China where the Dadiwan culture flourished between 8000-6000 y BP when the monsoon rains were abundant. The monsoon variability of the last 1000 years is discussed in conjunction with major political and historical development of Asia, with particular reference to the rise and fall of the Moghul Empire in south Asia (1500-1700 AD). The last section of this chapter deals with the possible impact of present climate change on future monsoon circulation and intensity. This discussion appears to be strongly influenced by the IPCC (2001) projections of significant melting of the Greenland Ice cap leading to an abrupt weakening of the ‘North Atlantic heat conveyer belt’ and this in turn could lead to a weakening of the Asian monsoon. Studies published in the last five years do not support such scenarios. A study by Kripalani et al (2003 Natural Hazards June 2003) shows that the Indian monsoon, and by extension the Asian monsoon, while exhibiting decadal variability with a 30-year cycle, is not influenced by global warming, and the recent 2007 IPCC documents on climate change suggest only a small change (less than 5%) in monsoon intensity over the next 25 to 30 years. Another recent study (Latif et al J of Climate September 2006) concludes that the recent observed weakening of the MOC (Meridional Overturning Circulation) in the North Atlantic is part of natural variability and not a result of global warming. Finally, there is considerable uncertainty in projections of future melting of the Greenland Ice cap with publication of several recent studies suggesting that the future warming of the earth’s climate due to a doubling of (human-added) atmospheric carbon dioxide may only be about 1°C or so.

In summary, this is a comprehensive book for someone whose interest is in the climate history of the Asian monsoon over last several million years. The Asian monsoon is perhaps the most complex feature of the earth’s climate system and per a recent paper (Shukla Science October 2007) the present climate models cannot adequately simulate the monsoon intensity and its interannual variability. The Indian and Asian Monsoon have witnessed large-scale droughts and floods in the past and will continue to do so, global warming notwithstanding. An important research area at present is the study of interannual variability of Asian monsoon and prediction of future droughts and floods. Such a study and the operational knowledge derived from it may enable many Asian countries to develop suitable adaptation measures so as to adjust to the vagaries of future monsoons.

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New Paper “Effects Of Global Irrigation On The Near-Surface Climate” by Sacks Et Al 2009

There is another paper in a continuing long stream of peer reviewed contibutions that document the role of the human management of the landscape on the climate system.

This new paper is

Sacks, W.J., B.I. Cook, N. Buenning, S. Levis, and J.H. Helkowski, 2009: Effects of global irrigation on the near-surface climate. Clim. Dynam., 33, 159-175, doi:10.1007/s00382-008-0445-z.

The abstract reads

“Irrigation delivers about 2,600 km3 of water to the land surface each year, or about 2% of annual precipitation over land. We investigated how this redistribution of water affects the global climate, focusing on its effects on near-surface temperatures. Using the Community Atmosphere Model (CAM) coupled to the Community Land Model (CLM), we compared global simulations with and without irrigation. To approximate actual irrigation amounts and locations as closely as possible, we used national-level census data of agricultural water withdrawals, disaggregated with maps of croplands, areas equipped for irrigation, and climatic water deficits. We further investigated the sensitivity of our results to the timing and spatial extent of irrigation. We found that irrigation alters climate significantly in some regions, but has a negligible effect on global-average near-surface temperatures. Irrigation cooled the northern mid-latitudes; the central and southeast United States, portions of southeast China and portions of southern and southeast Asia cooled by ~0.5 K averaged over the year. Much of northern Canada, on the other hand, warmed by ~1 K. The cooling effect of irrigation seemed to be dominated by indirect effects like an increase in cloud cover, rather than by direct evaporative cooling. The regional effects of irrigation were as large as those seen in previous studies of land cover change, showing that changes in land management can be as important as changes in land cover in terms of their climatic effects. Our results were sensitive to the area of irrigation, but were insensitive to the details of irrigation timing and delivery.”

The conclusion includes the text

“Global patterns of irrigation alter climate significantly in some large regions of the planet. Cooling effects tend to be greatest near irrigated areas in the season of heaviest irrigation, and are generally greater in dry regions. Consequently, irrigation appears to have caused the greatest cooling in northern mid-latitude regions. The effects are generally larger during the day than at night. While direct evaporative cooling is important, at least as much cooling seems to be caused by indirect effects such as increased cloud cover. The cooling in some regions, however, is offset by warming in other regions, predominantly the northern high latitudes, at least in our model. Dynamical changes, such as a slight strengthening of the Aleutian Low, seem primarily responsible for this high-latitude warming. On the global average, therefore, irrigation has a negligible effect on the near-surface temperature”


“The large effects of irrigation in some regions show that changes in land management can be as important for climate as changes in land cover. These changes in land management should be given greater attention, both for modeling future climate and for understanding historical climate trends……..It is important to consider how these irrigation changes will interact with other future climatic changes.”

This study documents why landscape change must be a major focus in climate assessments. It also show why the use of a global average surface temperature is useless to diagnose these climate effects.

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What Does A Global Average 2 Degrees C Increase Mean With Respect To Upper Ocean Heat Content Change? Part II

As was discussed in Part I (see), there are major biases and uncertainties with using a global average surface temperature, T’, to monitor and predict global warming.  This weblog explores ways to relate upper ocean heat content change to a temperature trend.

We could, perhaps, obtain T’ from the upper ocean heat data reported by Jim Hansen (see), where he wrote

“The Willis et al. measured heat storage of 0.62 W/m2 refers to the decadal mean for the upper 750 m of the ocean. Our simulated 1993-2003 heat storage rate was 0.6 W/m2 in the upper 750 m of the ocean. The decadal mean planetary energy imbalance, 0.75 W/m2, includes heat storage in the deeper ocean and energy used to melt ice and warm the air and land. 0.85 W/m2 is the imbalance at the end of the decade.”

The 0.62 W/m2 corresponds to 1.01 x 10**23 Joules per decade.  This rate is close to that seen in the analysis of Levitus et al (2009) [see]. As discussed on my weblog (see), this rate has not persisted since 2003, however, the value of 1.01 x 10**23 Joules per decade can be used to estimate how long different depths of the upper ocean would require at this rate to warm to a uniform temperature of 2C. While, the upper ocean does not warm uniformly in the vertical, a uniform value provides an estimate for the time required a layer of the ocean to warm to 2C at this rate [which is about 200 years].

In order to examine this issue, I contacted Josh Willis, and he graciously interacted via e-mail on this subject (I summarized my e-mails into a set questions). Below are his comments (presented with his permission):

Topic 1: What if the 2C warming was specified to be uniform to 700m (which is the depth Jim Hansen refers to in the above comment)?  [according to Josh, to warm the upper 700m of the ocean uniformly to 2C would require 2.036**24 Joules]
Josh Willis’s reply

“The problem I see [this] calculation is that it assumes that there is a uniform 2C warming over the entire upper 700 m of the water column.  This does not happen.  Rather, in the global average the heat mixes downward slowly from the surface over time.  As a result, the surface usually warms much faster than at depth.  So a 2C warming at the surface is unlikely to happen at the same time as a 2C warming at 700m.  Furthermore, the decrease of temperature with depth is unlikely to be linear.  Levitus has noted in past papers that most of the heat content increase is actually contained in the upper 300 m, for instance.

Using the most recent analysis from Levitus, the highest rate of ocean warming over the past 50 years occurse near the surface and is about 0.4C. During this time, upper ocean heat content rose by about 1 x 10**23 J. Assuming the relationship between surface warming and ocean heat content holds over longer time scales (i.e., that the ocean continues to mix heat down at a similar rate as it has in the past), then it would take only 5 x 10^23 J of ocean heat content increase to get 2C warming at the surface”

Topc 2: What is the depth we should use to estimate an upper ocean T’? Should this be the layer down to the thermocline? Clearly, it should not just be the sea surface value of T’, since the layers of the ocean that are close to the surface interact at short time scales with the atmopshere through latent and sensible turbulent heat fluxes

Josh Willis’s reply

“Understanding the vertical distribution of heat is still a bit tricky, I guess.  The global mean temperature of the ocean drops from about 18C at the surface to 4C at 1000 m.  By 200m, it is about 12C, by 300 m, it is about 10C and by 500 m, it is close to 7C.  So in the globally averaged sense, the thermocline is not all that sharp.  Of course, the depth of the  varies strongly with latitude as well.

In one sense, the 300m depth might work best because we actually have good historical measurements of this layer and it does seem to include most of the signal for the upper kilometer or so of ocean heat content changes on multi-decadal time scales.

Another volume of climatic relevance, however, would be the depth of the mixed layer, something like 60 m in the global average.

My Conclusion

The use of Joules by itself is all that is needed to quantify global warming and cooling. However, if the policymakers insist on the use of a T’, this temperature can be improved over what is used now.

By determining the layer of the ocean that interacts with the atmosphere on relatively short time periods (e.g. several years), than the T’ of this layer could be used to communicate the magnitude of global warming to policymakers. The oceanographic community should recommend the depth of the ocean to compute the most appropriate value of T’, as well as compute this value of T’, and disseminate this information to the climate science community, policymakers and the public.

Since such a value of T’ is a mass weighted average, it is a more robust method than using just a T” diagnosed from the surface temperature of the ocean. The oceanographic community should propose a method to do this, and the climate modeling community should adopt it as one of their metrics.


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What Does A Global Average 2 Degrees C Increase Mean With Respect To Upper Ocean Heat Content Change? Part I

In the media, there is considerable discussion as to the serious consequences to the environment and society, if the global average surface temperature increases to and beyond 2C from its pre-industrial value; for example, see Times Online on July 9 2009 where they wrote

“For the first time, America and the other seven richest economies agreed to the goal of keeping the world’s average temperature from rising more than 2C (3.6F).”

This temperature, however, is not one that can be directly measured as a single value. Rather, as discussed on page 21 in NRC (2005),  it is a derived temperature from the relationship between the global average radiative imbalance and is defined by the equation

                                                           dH/dt = f – T’/λ     (1)

where H is the heat content in Joules of the climate system, f is the radiative forcing at the top of the tropopause, T’ is the change in surface temperature in response to a change in heat content, and λ is the climate feedback parameter [which more accurately should be called the "temperature feedback parameter" since climate is much more than what is represented by this one equation]. Equation (1) above as a thermodynamic proxy for the thermodynamic state of the Earth system, as we wrote in our 2007 JGR paper.

The concept of a 2C threshold is based on equation (1).

However, how is T’ obtained? The approach is discussed in CCSP (2006) where land and ocean surface temperature anomalies are collected and the long term trend of the interpolated global average anomaly are used to obtain a value for T’. This involves ship and bouy measurements, and sea surface temperature observations from satellite, over the ocean, and surface weather stations over land. The land observations use the mean of the maximum and minimum temperatures to contruct the anomalies.

However, to compute dH/dt [which is the actual global warming], one needs to know the magnitude of the “temperature feedback parameter” and the radiative forcing in addition to  T’.

As documented in detail, this approach has major flaws which we reported 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.

In our paper we wrote

“This paper documents various unresolved issues in using surface temperature trends as a metric for assessing global and regional climate change. A series of examples ranging from errors caused by temperature measurements at a monitoring station to the undocumented biases in the regionally and globally averaged time series are provided. The issues are poorly understood or documented and relate to micrometeorological impacts due to warm bias in nighttime minimum temperatures, poor siting of the instrumentation, effect of winds as well as surface atmospheric water vapor content on temperature trends, the quantification of uncertainties in the homogenization of surface temperature data, and the influence of land use/land cover (LULC) change on surface temperature trends.”

 We concluded that

” As reported by Pielke [2003], the assessment of climate heat system changes should be performed using the more robust metric of ocean heat content changes rather than surface temperature trends…….This paper presents reasons why the surface temperature is inadequate to determine changes in the heat content of the Earth’s climate system.”

The assessment of changes in heat content directly [H in equation (1)]  removes the need to compute a “temperature feedback parameter” (λ) and T’. The changes in H can be used to diagnose the radiative imbalance (the sum of the radiative forcings and feedbacks) as discussed in

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

Clearly. the use of T’ as a diagnostic climate metric for global warmng and cooling is a convuluted way to obtain the heating of the climate system (i.e. “dH/dt”). The quantity “dH/dt” is the proper metric of global heat change in the units of heat added or removed (which is in units of Joules). However, scientists and policymakers insist on using T’ as the metric to discuss global warming.

Thus, if there is an insistence to limit global warming to a 2C increase, what does this translate to in terms of an increase in Joules of heat content in the ocean?

I will discuss this in Part II.

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A New Paper “A Case Study on Wintertime Inversions in Interior Alaska with WRF” by Mölders and Kramm 2009

There is a new paper which is directly related to the ability of models to skillfully simulate temperatures in the lowest levels of the atmosphere. This includes, of course, the 2m level which was discussed in several recent Climate Science weblogs (seesee and see). 

The new paper is

Mölders, N., and G. Kramm, 2009: A case study on wintertime inversions in Interior Alaska with WRF, Atmos. Res., doi:10.1016/j.atmosres.2009.06.002, in press.

The abstract reads

“The Weather Research and Forecasting (WRF) model is run in various configurations for a five day cold weather period with multi-day inversions over Interior Alaska. Comparison of the simulations with radiosonde data and surface observations shows that WRF’s performance for these inversions strongly depends on the physical packages chosen. Simulated near-surface air temperatures as well as dew-point temperatures differ about 4 K on average depending on the physical packages used. All simulations have difficulties in capturing the full strength of the surface temperature inversion and in simulating strong variations of dew-point temperature profiles. The greatest discrepancies between simulated and observed vertical profiles of temperature and dew-point temperature occur around the levels of great wind shear. Out of the configurations tested the radiation schemes of the Community Atmosphere Model combined with the Rapid Update Cycle land surface model and modified versions of the Medium Range Forecast model’s surface layer and atmospheric boundary layer schemes capture the inversion situation best most of the time.”

This paper confirms that the accurate paramterization of the temperatures at 2m is a challenge. The abstract writes

“Simulated near-surface air temperatures as well as dew-point temperatures differ about 4 K on average depending on the physical packages used. All simulations have difficulties in capturing the full strength of the surface temperature inversion and in simulating strong variations of dew-point temperature profiles.”

The same type of inaccurate paramterizations is used in the multi-decadal global climate models that were used in the 2007 IPCC report.

Since the errors are several degrees within stable atmospheric boundary layers (which are typical at night over land almost everywhere, and in the higher latitude winters all day), there should no confidence in the ability of these IPCC modes to skillfully predict the change in 2m temperatures for these conditions decades into the future [the 2m temperatures are used in the construction of the global average surface temperature trends].

This paper further illustrates major problems with using surface temperature trends to diagnose and predict global warming and cooling, as we have discussed, for example, 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,

and, see also, the excellent guest weblog by Professor McNider,

In the Dark of the Night – the Problem with the Diurnal Temperature Range and Climate Change by Richard T. McNider.



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