Monthly Archives: January 2009

Modeling Aerosol-Radiation-Cloud And Precipitation Processes In The Mediterranean Region By Kallos Et Al. 2008

One of my colleagues, who I have the highest respect for, Professor George Kallos of the University of Athens, has another excellent study of a weather and climate issue, which is reported on below.

A presentation in Cyprus entitled Modeling Aerosol-Radiation-Cloud and Precipitation Processes in the Mediterranean Region by George Kallos and colleagues from the University of Athens School of Physics, Atmospheric Modeling and Weather Forecasting Group. The motivation for the study are listed as:

  • Physiographic characteristics are partially responsible for the formation of particular climatic conditions in the Mediterranean Region.
  • Regional climatic patterns are defined as a result of balancing between large scale flow and mesoscale circulations.
  • The resulted circulation has a general trend from North to South (pressure gradient and differential heating between land and water).
  • Air masses reaching the Mediterranean region are not clearly defined as pure maritime or continental because their characteristics are modified relatively fast.
  • The air masses in the area have a mixture of natural and anthropogenic origin aerosols with varying optical and hygroscopic properties.
  • Therefore, aerosol-cloud-radiation processes have some unique characteristics.
  • Desert dust and sea salt are major sources of PM [particulate matter] in the atmosphere.
  • Their impacts in the atmosphere are many and of course the feedbacks are considerable.
  • The impacts are ranging from modification of the radiative forcing to cloud formation and precipitation.
  • Therefore, perturbations in dust and/or sea salt particle production can have impacts on radiative properties, cloud formation and water budget.
  • These links are not one way but there are feedbacks that are critical for both meteorological and climatological-scale phenomena.
  • The links and feedbacks become more complicated because of the coexistence of anthropogenically-produced aerosols and chemical transformations.

This presentation was also provided by Dr. Kallos in describing CIRCE: Climate Change and Impact ResearCh: the Mediterranean Environment

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Follow Up On Today’s AP Article By Seth Bornenstein Entitled “Study: Antarctica Joins Rest Of Globe In Warming”

An AP article was released today which reports on a Nature paper on a finding of warming over much of Antarctica. I was asked by Seth Borenstein to comment on the paper (which he sent to me). I have been critical of his reporting in the past, but except for the title of the article (which as I understand is created by others), he presented a balanced summary of the study.

My reply to Seth is given below.

 I have read the paper and have the following comments/questions

1. The use of the passive infrared brightness temperatures from the AVHRR
   (a polar orbiting satellite) means that only time samples of the
   surface temperature are obtained. The surface observations, in
   contrast, provide maximum and minimum temperatures which are used to
   construct the surface mean temperature trend. The correlation between
   the two data sets, therefore, requires assumptions on the temporal
   variation of the brightness temperature at locations removed from the
   surface in-situ observations. What uncertainty (quantitatively)
   resulted from their interpolation procedure?

2. Since the authors use data from 42 occupied stations and 65 AWSs sites,
   they should provide photographs of the locations (e.g. as provided in in order to
   ascertain how well they are sited. This photographs presumably exist.
   Do any of the surface observing sites produce a possible bias because
   they are poorly sited at locations with significant local human
   microclimate modifications?

3. How do the authors reconcile the conclusions in their paper with the
   cooler than average long term sea surface temperature anomalies off of
   the coast of Antarctica? [see].
   These cool anomalies have been there for at least several years. This
   cool region is also undoubtedly related to the above average Antarctic
   sea ice areal coverage that has been monitored over recent years; see].

4. In Figure 2 of their paper, much of their analyzed warming took place
   prior to 1980. For East Antarctica, the trend is essentially flat since
   1980. The use of a linear fit for the entire period of the record
   produces a larger trend than has been seen in more recent years.

In terms of the significance of their paper, it overstates what they have obtained from their analysis. In the abstract they write, for example,

“West Antarctic warming exceeds 0.1C per decade over the past 50 years”.

However, even a cursory view of Figure 2 shows that since the late 1990s, the region has been cooling in their analysis in this region. The paper would be more balanced if they presented this result, even if they cannot explain why.

Please let me know if you would like more feedback. Thank you reaching out to include a broader perspective on these papers in your articles.



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An Obvious Double Standard Adopted By The AGU Publication EOS

In the January 20, 2009 issue of the AGU publication EOS, there is Feature article by P.T. Doran and M. K. Zimmerman titled “Examining the Scientific Consensus on Climate Change”.

This paper is a polling paper that specifically reported in the EOS article on the two questions:

1. When compared with pre-1800s levels, do you think that mean global temperatures have generally risen, fallen, or remained relatively constant?
2. Do you think human activity is a significant contributing factor in changing mean global temperatures?

The conclusion in the article is that

“It seems that the debate on the authenticity of global warming and the role played by human activity is largely nonexistent among those who understand the nuances and scientific basis of long-term climate processes. The challenge, rather, appears to be how to effectively communicate this fact to policy makers and to a public that continues to mistakenly perceive debate among scientists.”

However, EOS rejected our polling study last year, as we reported on in Climate Science in the weblogs

Is There Agreement Amongst Climate Scientists on the IPCC AR4 WG1?

Follow Up By Fergus Brown To “Is There Agreement Amongst Climate Scientists on the IPCC AR4 WG1?”

In the first weblog, I wrote

“After the survey was completed last summer and the article written, it was submitted to the AGU publication EOS as a “Forum piece. The EOS description of a Forum is that it

 ”contains thought-provoking contributions expected to stimulate further discussion, within the newspaper or as part of Eos Online Discussions. Appropriate Forum topics include current or proposed science policy, discussion related to current research in our fields especially scientific controversies, the relationship of our science to society, or practices that affect our fields, science in general, or AGU as an organization. Commentary solely on the science reported in research journals is not appropriate.”

Our article certainly fits this description.  However, after 4 months without a decision, our contribution was summarily rejected by Fred Spilhous without review. He said our article did not fit EOS policy. We disagreed, of course, based on the explicit EOS policy given above, but our follow request for an appeal was ignored.”

Thus, EOS accepts a poll P.T. Doran and M. K. Zimmerman (as a Feature), yet rejected our contribution which was submitted as a Forum contribution. This is an obvious double standard, and raises serious questions on the role of EOS as an objective vehicle to communicate climate science issues.

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Predicted Climate Cooling – Another Example Of Overstating Our Understanding Of Climate Science

There have been claims that the Earth is entering period of strong climate cooling; e.g. see

Earth on the Brink of an Ice Age

Such predictions of cooling, however, are no more substantiated by skillful validated predictions of this cooling, than are the IPCC predictions of more-or-less uniform global warming.

What the science does tell us is that the human influence on climate is significant and involves a diverse range of first-order climate forcings, including, but not limited to the human input of CO2 (e.g. see). Natural variations are important (and still not yet adequately understood; e.g. see), and the human influence is also significant and involves a diverse range of first-order climate forcings (including, but not limited to the human input of CO2).

To assume we understand enough about natural climate variations and long term trends to skillfully predict a sudden cooling of the global climate is not supported by peer reviewed scientific research.  We need to recognize that accurate climate prediction is a much more daunting challenge than is reported in the news article above, and in the 2007 IPCC report.

For summary of the Climate Science perspective on climate, please see my 2007 House testimony.


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Comments On Real Climate’s Post “FAQ on climate models: Part II”

Real Climate has a weblog titled “FAQ on climate models: Part II”.

Climate Science has a response to several of the questions that are posed there as well as questions for Gavin Schmidt [who wrote the Real Climate Q&A].  Climate Science has already posted on Part I of the Real Climate FAQs; see

Real Climate Misunderstanding Of Climate Models,

which Gavin has either not seen, or cared to respond to. In either case, he continues to incorrectly communicate important aspects of modeling on Real Climate.

 Q & A by Gavin Schmidt

  • What are parameterisations?
  • Some physics in the real world, that is necessary for a climate model to work, is only known empirically. Or perhaps the theory only really applies at scales much smaller than the model grid size. This physics needs to be ‘parameterised’ i.e. a formulation is used that captures the phenomenology of the process and its sensitivity to change but without going into all of the very small scale details. These parameterisationsare approximations to the phenomena that we wish to model, but which work at the scales the models actually resolve. A simple example is the radiation code – instead of using a line-by-line code which would resolve the absorption at over 10,000 individual wavelengths, a GCM generally uses a broad-band approximation (with 30 to 50 bands) which gives very close to the same results as a full calculation. Another example is the formula for the evaporation from the ocean as a function of the large-scale humidity, temperature and wind-speed. This is really a highly turbulent phenomena, but there are good approximations that give the net evaporation as a function of the large scale (‘bulk’) conditions. In some parameterisations, the functional form is reasonably well known, but the values of specific coefficients might not be. In these cases, the parameterisations are ‘tuned’ to reproduce the observed processes as much as possible. 

    R.A. Pielke Sr. Answer

    The only basic physics in the models are the pressure gradient force, advection and the acceleration due to gravity. These are the only physics in which there are no tunable coefficients. Climate models are engineering codes and not fundamental physics. If Gavin concludes otherwise, he should provide examples of any parametrization that does not use tunable empirically derived coefficients.  Also, he should provide examples of where the “functional form” is reasonably well known. This is true for a few types of processes, such as turbulence very near the surface, and for clear sky long- and short-wave radiative fluxes, but is not true for most other parametrizations.

    The detailed form of the parameterizations of the atmospheric part of climate models is presented in

    Pielke, R.A., Sr., 2002: Mesoscale meteorological modeling. 2nd Edition, Academic Press, San Diego, CA, 676 pp.

    Request: Gavin should document the number of parameters used in each of the parameterizations used in the GISS model (or refer us to papers where this appears).

    Q & A by Gavin Schmidt

  • How are the parameterisations evaluated?
  • In at least two ways. At the process scale, and at the emergent phenomena scale. For instance, taking one of the two examples mentioned above, the radiation code can be tested against field measurements at specific times and places where the composition of the atmosphere is known alongside a line-by-line code. It would need to capture the variations seen over time (the daily cycle, weather, cloudiness etc.). This is a test at the level of the actual process being parameterised and is a necessary component in all parameterisations. The more important tests occur when we examine how the parameterisation impacts larger-scale or emergent phenomena. Does changing the evaporation improve the patterns of precipitation? the match of the specific humidity field to observations? etc. This can be an exhaustive set of tests but again are mostly necessary. Note that most ‘tunings’ are done at the process level. Only those that can’t be constrained using direct observations of the phenomena are available for tuning to get better large scale climate features. As mentioned in the previous post, there are only a handful of such parameters that get used in practice.

    R.A. Pielke Sr. Answer

    The statement by Gavin that

    “The more important tests occur when we examine how the parameterisation impacts larger-scale or emergent phenomena”

    is not correct. Both the process and emergent scales must be accurately modeled. How can the emergent scale be represented skillfully unless the process scale is accurate?

    Regarding the statement by Gavin that, with respect to emergent scales,

    “As mentioned in the previous post, there are only a handful of such parameters that get used in practice”

    this is quite an admission.

    Request: Gavin should tell us what are the handful of such parameters used in the GISS model.

     Q & A by Gavin Schmidt

    What are the differences between climate models and weather models?

    “Conceptually they are very similar, but in practice they are used very differently. Weather models use as much data as there is available to start off close to the current weather situation and then use their knowledge of physics to step forward in time. This has good skill for a few days and some skill for a little longer. Because they are run for short periods of time only, they tend to have much higher resolution and more detailed physics than climate models (but note that the Hadley Centre for instance, uses the same model for climate and weather purposes). Weather models develop in ways that improve the short term predictions, though the impact for long term statistics or the climatology needs to be assessed independently. Curiously, the best weather models often have a much worse climatology than the best climate models. There are many current attempts to improve the short-term predictability in climate models in line with the best weather models, though it is unclear what impact that will have on projections.”

    R.A. Pielke Sr. Answer

    Weather models are different from climate models for two main reasons. Weather models focus on the atmospheric part of the climate system and, very importantly, use observed values of temperature, humidity, and winds (and other weather variables, such as cloud information) within the atmosphere as initial conditions. Skill in weather prediction is lost when the memory of these initial conditions is lost.

    Gavin’s claim thatCuriously, the best weather models often have a much worse climatology than the best climate models”, is an odd statement, since the weather models use real world observed data! This claim needs to be supported by referring us to peer reviewed studies.

    Moreover, as written earlier in my response, weather and climate models are both engineering code in which, of the physical, biological and chemical processes within climate models, only the pressure gradient force, advection and gravity are fundamental physics. All other physical, chemical and biological processes are parameterized.

    In order to insure that the dynamics of the atmospheric weather features are accurately predicted (which tests the representation of the pressure gradient force and advection, and of the parameterizations, within the models), the climate models should be run in the weather prediction mode. To my knowledge, the GISS model, and most of the IPCC models, have not completed such an engineering test.

    Request: Gavin should tell us why not, or if GISS has completed such a test, provide us the relevant reports or research articles.

    I will also post the url of this weblog on Real Climate. If Gavin is interested in a constructive scientific exchange, he will welcome this debate, and respond accordingly.

    Update: Here is the comment I submitted to be posted on Real Climate

    “Gavin – I have posted a weblog which questions several of your answers []. I would be glad to post as a guest weblog your responses on Climate Science. Roger”

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    Record Temperature Data At The Weblog Hall Of Record

    Bruce Hall has an excellent presentation of temperature records in the United States on his weblog.

    Among his valuable comments, he writes

    “The U.S. analysis showed that the late 1990s were indeed hot and had a greater than normal expected level of statewide monthly records. What it also showed, however, was that the 1930s had a much higher frequency of those records. Finally, it showed a sharp tailing off of such extremes beginning with the new century.

    I have completed the review of the high temperature extremes through 2008 and there were no additional statewide month high temperature records. An analysis of the 2005 – 2008 data for minimum temperature records will be started shortly.”

    His entire posting is worth reading.

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    Filed under Climate Change Metrics

    Incorrect Comment On Real Climate

    Update: There is discussion on Real Climate, in response to my posting of the announcement of this Climate Science weblog on that site [see #251 and #253 from Hank Roberts]. Here is what I just posted on Real Climate’s comment section;

    “Hi Hank – Re #251 and #253 Thank you for clarifying. I do hope, however, there is discussion on Real Climate (in the comments, if not a weblog), the issues that I raised in my Physics Today article.”

    The Real Climate weblog by Gavin Schmidt of January 14 2009 titled “CNN is spun right round, baby, right round” had the following comment (#149) by John L. that read

    I am unclear on what is being said here:

    “..No model predicted the current cooling temperatures before they occurred.

    [Response: That is not correct. Current temperatures are within the ensemble of model runs, and over short periods, models often show coolings. Conflation of the expected long term trend with a single realisation of the weather is an all-too-common error. – gavin]”

    Are you saying that no model could predict the cooling trend (presumably because they do not have such specificity of result), that any result within a range of probability for all models is “predicted”, or that a specific model did predict the cooling trend?

    [Response: The original claim implies that the current temperatures are out of line with all models. This is incorrect. For the period highlighted in the link (which, by the way does not make that claim about the models), 2003 to 2007, the range of model trends in SAT in the AR4 archive is [-0.40,0.95] deg C/decade – indicating clearly that short term trends are not useful for climate model evaluation. – gavin]

    Comment by John L — 16 January 2009 @ 5:18 PM

    The Commenter’s quote is not from my Physics Today paper. Gavin Schmidt’s answer also clearly shows that he has not read my paper. The correct information from

    Pielke Sr., R.A., 2008: A broader view of the role of humans in the climate system. Physics Today, 61, Vol. 11, 54-55

        “Although four years is a relatively short period of analysis, the absence of heating of the magnitude reported by Hansen and his collaborators and the 2007 IPCC report should raise issues with respect to our understanding of the climate system, since the global model projections used by the IPCC predict more or less monotonic accumulation of heat in the Earth System.”

    I recommend readers (and Gavin Schmidt) read the entire article.

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    Congratulations To Anthony Watts For His Well Deserved Recognition!

    Anthony Watts has won the best science weblog for 2008; see The 2008 Weblog Awards Winners.

     This is an appropriate and well deserved recognition of the importance of Anthony’s weblog Watts Up With That, which is providing a much needed discussion of climate science. We all should look forward to another year of accomplishments and issues from this outstanding website!


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    Long-Range Transport of Anthropogenically and Naturally Produced Particulate Matter in the Mediterranean and North Atlantic: Current State of Knowledge by Kallos et al. 2007

    There is a valuable research paper that documents the important role of aerosols on weather and climate, with an emphasis on their transport across long distances. The paper, by an outstanding scientist at the University of Athens, is

    Kallos, G., M. Astitha, P. Katsafados, and C. Spyrou, 2007: Long-Range Transport of Anthropogenically and Naturally Produced Particulate Matter in the Mediterranean and North Atlantic: Current State of Knowledge. J. Appl. Meteor. Climatol., 46, 1230–1251.

    The abstract reads

    “During the past 20 years, organized experimental campaigns as well as continuous development and implementation of air-pollution modeling have led to significant gains in the understanding of the paths and scales of pollutant transport and transformation in the greater Mediterranean region (GMR). The work presented in this paper has two major objectives: 1) to summarize the existing knowledge on the transport paths of particulate matter (PM) in the GMR and 2) to illustrate some new findings related to the transport and transformation properties of PM in the GMR. Findings from previous studies indicate that anthropogenically produced air pollutants from European sources can be transported over long distances, reaching Africa, the Atlantic Ocean, and North America. The PM of natural origin, like Saharan dust, can be transported toward the Atlantic Ocean and North America mostly during the warm period of the year. Recent model simulations and studies in the area indicate that specific long-range transport patterns of aerosols, such as the transport from Asia and the Indian Ocean, central Africa, or America, have negligible or at best limited contribution to air-quality degradation in the GMR when compared with the other sources. Also, new findings from this work suggest that the imposed European Union limits on PM cannot be applicable for southern Europe unless the origin (natural or anthropogenic) of the PM is taken into account. The impacts of high PM levels in the GMR are not limited only to air quality, but also include serious implications for the water budget and the regional climate. These are issues that require extensive investigation because the processes involved are complex, and further model development is needed to include the relevant physicochemical processes properly.”

    Among the conclusions is the finding that

    “Climate and air-quality feedbacks are not well understood, and hence future work requires specialized surface and upper-air measurements to explore the validity validity of the various model elements.”

    It should be obvious, that skillful multi-decadal climate predictions cannot be made, despite claims by the IPCC and CCSP assessemnts that this is possible.


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    Filed under Climate Change Forcings & Feedbacks, Climate Models

    Guest Weblog By Madhav Khandekar

    There is an article in Science [H/T to W. F. Lenihan!] 

     Historical Warnings of Future Food Insecurity with Unprecedented Seasonal Heat
    David. S. Battisti and Rosamond L. Naylor Science 9 January 2009: 240-244.

    The abstract of this article reads

    “Higher growing season temperatures can have dramatic impacts on agricultural productivity, farm incomes, and food security. We used observational data and output from 23 global climate models to show a high probability (>90%) that growing season temperatures in the tropics and subtropics by the end of the 21st century will exceed the most extreme seasonal temperatures recorded from 1900 to 2006. In temperate regions, the hottest seasons on record will represent the future norm in many locations. We used historical examples to illustrate the magnitude of damage to food systems caused by extreme seasonal heat and show that these short-run events could become long-term trends without sufficient investments in adaptation.”

    An excellent weblog by Pat Michaels on  this Science paper is also worth reading (see).

     Madhav Khandekar has e-mailed me on this article, and graciously accepted my invitation to post as a guest weblog his insightful comments on this paper. Dr. Khandekar is an Environmental Consultant (extreme weather events) and worked for 25 years with Environment Canada in Meteorology. His weblog follows.

    Guest Weblog by Madhav Khandekar

    “I read the abstract and summary of David Battisti’s article from Science and am very disappointed at his naive analysis of “hot” future climate and its possible adverse impact on world-wide and in particular tropical agriculture. I am afraid he ( David) has NOT tried to understand or analyze in depth how agriculture has evolved in most tropical regions.

     From my limited analysis of agricultural evolution over south Asia (where more than 60% of humanity lives today) most regions have substantially increased their grain & food ( fruits, veggies etc) supply in the last 25 yrs. Increase in max temp (due to GW) alone is NOT necessarily deleterious to agriculture in Asia and tropical Africa. Reduced rainfall ( seasonal, Monsoonal) can be more deleterious to agriculture and so far there is NO indication that Monsoon or seasonal rains over Asia & tropical Africa have declined in the last 25 yrs.Allow me to provide some numbers: For India ( I have done extensive analysis of Monsoon and agriculture for India) the rice yield has increased from 25 M tonnes in 1950 to about 100 M tonnes in recent yrs and most of India’s rice grows in the Peninsular India where mean temp has increased by about 1C over the past 50 yrs. During the Monsoon months mean temp is about 32/35c ( David refers to this as ‘critical’, which is NOT correct)  but with good rains from Monsoon season,rice can grow quite well there. In the northern Province of Punjab ( India’s wheat growing region) wheat grows due to winter
    rains ( December-March, about 6-10 cm) plus excellent irrigation ( perhaps best in the world) and today Punjab produces about 70 M tonnes of wheat, compared to about 15 M tonnes in the 1950s. Besides wheat & rice India also produces a variety of other grains like beans, sorghum, soya, barley etc. India has two agricultural seasons, Kharif the main Monsoon season,

    June-Sept and Rabi, winter season Dec-Feb this only for selected regions of Peninsular India and parts of central  & north India where irrigation is well developed. The two seasons’ total yield today can and does provide sufficient grains/fruits/veggies etc for 1.2 B people of India, this represents
    about 20% of world’s humanity!

    Based on limited analysis, I can say that “there is plenty of food today for most people in India ( there is NO starvation anywhere!). Admittedly, the prices of grains & veggies are yet NOT affordable to everyone. The Central Govt (in New Delhi) is doing its best to provide basic grains ( rice & wheat) to many rgions at subsidized prices.With general elections coming in the next three months or about, the ruling Govt in New Delhi will try its best to provide adequate food/grains to everyone so the next election will NOT be on “food shortage” issue, BUT most certainly on terrorism which is becoming the most talked about issue at present. Elsewhere in south Asia, food grains and fruits and veggies have registered increased yields in the last 25 yrs and most regions ( including Burma OR Myanmar where there is strict Military rule) have adequate food supply.

    In summary I completely disagree with David Battistie’s analysis of “reduced grain yield” in a warmer world! This issue is very poorly analyzed. Battistie gives example of the Sahel region, which is a poor example in my opinion. Battistie should know that the Sahel is NOT the grain basket for Africa. It produces a measly few M tonnes of peanuts, so why worry about possible depletion of few M tonnes of peanuts, while completely ignoring hundreds of M tonnes of grain being produced elsewhere? To give some more numbers: For the year May 2007 thru April 2008, India’s total grain yield, per an article I read in May 2008, was estimated at about 230 M tonnes, possibly largest yield in the last ten yrs. During an election in July/August 2008 in one of the southern Provinces in India, the New Delhi Govt was promising people there that “rice will be made available at Rs 20 per Kilo-this translates to about 50 cents (US) per kilo!” (Delhi Govt has purchased large quantities of wheat & rice for distribution at subsidized rates).

    p.s. I met Battistie at a CMOS ( Can Met & Oceanogr Soc) Annual Metting in Kelowna British Columbia in 1995. He is agood modeler and I had good discussion with him. I am afraid he puts “too much” faith in his models.”

    Dr. Khandekar added the further comments below after I requested permission to post as a guest weblog.

    You are most welcome to post my comments on your blog. I would feel honoured to see my comments on south Asia’s grain and food sufficiency over the last 25 yrs in your blog.

    Allow me to make few more observations: I visited two major cities of India New Delhi ( lat 30N Population ~ 11 M) and Hyderabad ( lat ~13N Population ~8 M) in the last year and was impressed to see both these cities full of vegetation and big shady trees providing a nice “green look” despite the fact that both these cities have hot summer climate with max temp reaching 42-45C at least ten days during the premonsoon months March-May. In New Delhi, India’s capital city, there is an area in Central Delhi ( close to the India Met Dept main office) called The Lodi Gardens, which is about 2 Sq Km area with lots of large trees providing excellent shade during hot summer days. These well-known Lodi Gardens were established by the Lodi Family which ruled New Delhi around 1000-1100 AD. It is interesting to note that these Gardens and the trees have survived the relatively cooler climate of the LIA ( Little Ice Age) and are thriving well, even during the hot summer days of New Delhi. I recall New Delhi recording max temp of 50C for about two weeks in June 1998, the so-called ‘hottest’ year as designated by the IPCC.

    Both New Delhi & Hyderabad have Monsoonal climate where summer ( June-September) rains provide the annual moisture ( about 20-25 inches of rains both places). New Delhi does get few cm of winter ( December-march) rains, while Hyderabad only occasionally gets some winter precipitation via Easterly Waves from the bay of Bengal ( in the east) of about 3-5 cm.

    Even the State of Rajasthan ( in Northwest India) which has a desert climate can and does support fair amount of greenery and large trees dotted along ‘old’ dried rivers as well as elsewhere in the State. Northwest India has experienced an interesting climate change over the last two thousand years ( recall Late Prof Reid Bryson’s study of the 1960s on ‘dust & climate” ) and there are numerous stories in the Hindu Mythology about the vanishing River Saraswati ( Goddess of Knowledge) which was full of water some 1500 years ago and is completely dry at present. There are plans at present to revive the old dry river bed to make it green again!

    When one closely analyzes the climate of India and south Asia, Battisti’s present study in Science seems deeply flawed.

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