October 6, 2008
There is an important new addition to the scientific discussion of Atlantic hurricane activity over the last century and a half. It is
Chylek, P., and G. Lesins (2008), Multi-decadal variability of Atlantic hurricane activity: 1851-2007, J. Geophys. Res., doi:10.1029/2008JD010036, in press.
The abstract reads
“An analysis of Atlantic hurricane data (HURDAT), using a hurricane activity index that integrates over hurricane numbers, durations and strengths during the years 1851-2007, suggests a quasi-periodic behavior with a period around 60 years superimposed upon a linearly increasing background. The linearly increasing background is significantly reduced or removed when various corrections were applied for hurricane under-counting in the early portion of the record. The periodic-like behavior is persistent in uncorrected HURDAT data as well as in data corrected for possible missing storms. The record contains two complete cycles: 1860-1920 and 1920-1980. The 2004 and 2005 hurricane seasons were unusual in that two intense hurricane seasons occurred in consecutive years. The probability for this happening in any given year is estimated to be less then 1%. Comparing the last 28 years (1980-2007) with the preceding 28 years (1953-1980) we find a modest increase in the number of minor hurricanes (category 1 and 2), however, we find no increase in the number of major hurricanes (category 3-5). The hurricane activity index is found to be highly correlated with the Atlantic Multi-decadal Mode (AMM).”
This analysis provides an important perspective of the variations in hurricane activity over time, which has not yet been accurately simulated (or predicted) by the multi-decadal global climate models. It shows that, even without the human intervention into the climate system, there are long time variations in Atlantic hurricane activity.
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October 3, 2008
An excellent new paper has appeared. It is
Campra, P., M. Garcia, Y. Canton, and A. Palacios-Orueta, 2008: Surface temperature cooling trends and negative radiative forcing due to land use change toward greenhouse farming in southeastern Spain,J. Geophys. Res., 113, D18109, doi:10.1029/2008JD009912.
The abstract reads
“Greenhouse horticulture has experienced in recent decades a dramatic spatial expansion in the semiarid province of Almeria, in southeastern (SE) Spain, reaching a continuous area of 26,000 ha in 2007, the widest greenhouse area in the world. A significant surface air temperature trend of −0.3°C decade−1in this area during the period 1983–2006 is first time reported here. This local cooling trend shows no correlation with Spanish regional and global warming trends. Radiative forcing (RF) is widely used to assess and compare the climate change mechanisms. Surface shortwave RF (SWRF) caused through clearing of pasture land for greenhouse farming development in this area is estimated here. We present the first empirical evidences to support the working hypothesis of the development of a localized forcing created by surface albedo change to explain the differences in temperature trends among stations either inside or far from this agricultural land. SWRF was estimated from satellite-retrieved surface albedo data and calculated shortwave outgoing fluxes associated with either uses of land under typical incoming solar radiation. Outgoing fluxes were calculated from Moderate Resolution Imaging Spectroradiometer (MODIS) surface reflectance data. A difference in mean annual surface albedo of +0.09 was measured comparing greenhouses surface to a typical pasture land. Strong negative forcing associated with land use change was estimated all year round, ranging from −5.0 W m−2 to −34.8 W m−2, with a mean annual value of −19.8 W m−2. According to our data of SWRF and local temperatures trends, recent development of greenhouse horticulture in this area may have masked local warming signals associated to greenhouse gases increase.”
The introduction reads in part
“Anthropogenic changes to the physical properties of the land surface can perturb the climate by altering the Earth’s radiative energy balance, and have been regarded as a cause of regional and even global climate change [Sagan et al., 1979]. Furthermore, land use changes are likely to be among the first drivers of climate change at meso- and local scales. Surface albedo affects the shortwave radiation budget by controlling how much incoming solar radiation is absorbed by the surface. Because of this, changes in surface albedo have been suspected of being the dominant influence of mid- and high-latitude land use change on climate [Betts, 2001]. Small changes in Earth’s albedo, even below satellite detection limits, can lead to global temperature changes equivalent to those associated with increase in greenhouse gases [Charlson et al., 2005].”
The conclusion has the text
“Our results show that, at local and meso-scale, greenhouse farming is very likely the most powerful driver of climate change in the area of study, probably due to the dramatic increase in surface albedo of the highly reflective plastic cover over a widespread agricultural area, which largely offsets positive forcing (+2 W m−2) very probably induced by global increase in greenhouse gases [Forster et al., 2007]. The main general implication of these findings is to highlight the importance of human development of high albedo surfaces in the strategies of mitigation and adaptation to global warming at local scale. However control stations records outside the GH area show that little or no effects on surface temperature extend far from the high albedo area, so the forcing caused by greenhouse development seems to be very localized.”
and
“The relative influence on local climate of other physical changes must be explored. The land use climate forcing that we have estimated here does not fully represent GH land use effects, as there are other changes in surface properties affecting the surface energy balance that have not been considered. For instance, eco-physiological and aerodynamic changes and alterations of roughness still remain undetermined. The complex role of evapotranspiration associated to this drip-irrigated soil under a plastic cover must be investigated [Fernandez et al., 2007]. Cooling effect of higher albedo could have been enhanced by the increase in latent heat flux derived from irrigation within the greenhouses (released as water vapor by greenhouses ventilation), with respect to previous pasture cover, further reducing sensible heat transfer and surface air temperature. On the contrary, irrigation might also cause a positive forcing by the increase in water vapor in the lower atmosphere [Boucher et al., 2004; Christy et al., 2006].”
The paper concludes with the text
“Even the RF [Radiative Forcing] concept might not be the most appropriate concept in our case, so that other alternative metrics [Pielke et al., 2002] could be advisable to estimate and model the net impact on the local climate of GH development.”
This paper provides further support for the viewpoint presented in
National Research Council, 2005: Radiative forcing of climate change: Expanding the concept and addressing uncertainties. Committee on Radiative Forcing Effects on Climate Change, Climate Research Committee, Board on Atmospheric Sciences and Climate, Division on Earth and Life Studies, The National Academies Press, Washington, D.C., 208 pp.
where it is written that
“Regional variations in radiative forcing may have important regional and global climatic implications that are not resolved by the concept of global mean radiative forcing.”
and
“Several types of forcings—most notably aerosols, land-use and land-cover change, and modifications to biogeochemistry—impact the climate system in nonradiative ways, in particular by modifying the hydrological cycle and vegetation dynamics.”
Reports such as the 2007 IPCC and the 2008 CCSP assessments are ignoring this peer reviewed issue. Poor policy decisions are being made because the concept of how humans are altering the climate system has not been properly communicated to the policymakers. This is a failure of the IPCC and CCSP process.
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October 2, 2008
Thanks to Timo Hämeranta for alerting us to the essay by the internationally well respected climate scientist Ann Henderson-Sellers on September 17 2008 titled “The IPCC report: what the lead authors really think”. It is worth reading and I have reproduced below:
“In the final months of the Intergovernmental Panel on Climate Change’s Fourth Assessment reporting in 2007, the world’s three leading climate science agencies asked people directly and intimately involved with the report for their views on how the process had gone and some of the key issues it raised.
The three agencies in question: the Global Climate Observing System Programme (GCOS), the World Climate Research Programme (WCRP), and the International Geosphere-Biosphere Programme (IGBP) are the world co-ordinators of observations and research on climate change. They also held a workshop in Sydney in October 2007 on Learning from the IPCC Fourth Assessment Report, for which I drafted an outline of a workshop paper, based entirely on responses to the survey.
Here I want to go back and check whether the first glimpse we received of the “real gut feeling” of some of the IPCC authors and co-ordinators as they finished up the humungous task of completing the Fourth Assessment Report held steadfast throughout the Sydney meeting process and the subsequent re-writings of views and clarification – and sometimes perhaps cleaning up – of opinions. I have done this because I believe it is essential for the climate change research community to be transparent and honest about what it can and cannot deliver and how, if ever, current inadequacies can be resolved.
What follows is the text I drafted one year ago which itself came entirely from quotes from IPCC lead authors responding to a questionnaire sent out by GCOS-WCRP-IGBP. The full details of the questionnaire and the replies submitted, some of which came in after this draft was written, have since been restricted but an early summary can still be found. (See related links).
In this article I report what these eminent folks said – every bullet point comprises a reply submitted by an IPCC respondent in mid-2007 and the only editing has been to improve the English, clarify or spell out acronyms.
Urgent policy issues that climate change research must tackle
• Monitoring the trajectory of climate change to assess whether we are heading into a danger-zone and how fast/where.
• Examining policy-driven questions to learn to understand how others see the world and what scientists need to do to help resolve such non-science priorities.
• Rolling reassessment building on what works, discarding what is weaker and revisiting with governments and stakeholders their priority needs.
• Establishing metrics of transient change impacts to detect and monitor the most likely (best predicted) changes of importance for rapid adaptation response.
• Assisting in determining what adaptation measures are needed beyond current coping capacity.
• Providing pathway options to obtain thresholds like the 2°C limit goal of the European Union.
• Fuller understanding of the carbon cycle and stabilizing emissions levels of greenhouse gases.
• Increasing confidence in the relationship between stabilizing emissions and temperature rise.
Serious inadequacies in climate change prediction that are of real concern
• The rush to emphasize regional climate does not have a scientifically sound basis.
• Prioritize the models so that weaker ones do not confuse/dilute the signals.
• Until and unless major oscillations in the Earth System (El Nino-Southern Oscillation (ENSO), Pacific Decadal Oscillation (PDO), North Atlantic Oscillation (NAO) and Atlantic Multidecadal Oscillation (AMO) etc.) can be predicted to the extent that they are predictable, regional climate is not a well defined problem. It may never be. If that is the case then we should say so. It is not just the forecast but the confidence and uncertainty that are just as much a key.
• Climate models need to be exercised for weather prediction; there are necessary but not sufficient things that can best be tested in this framework, which is just beginning to be exploited.
• Energy budget is really worrisome; we should have had 20 years of ERBE [Earth Radiation Budget Experiment] type data by now- this would have told us about cloud feedback and climate sensitivity. I’m worried that we’ll never have a reliable long-term measurement. This combined with accurate ocean heat uptake data would really help constrain the big-picture climate change outcome, and then we can work on the details.
• [Analyse] the response of models to a single transient 20th century forcing construction. The factors leading to the spread in the responses of models over the 20th century can then be better ascertained, with forcing separated out thus from the mix of the uncertainty factors. The Fourth Assessment Report missed doing this owing essentially to the timelines that were arranged.
• Adding complexity to models, when some basic elements are not working right (e.g. the hydrological cycle) is not sound science. A hierarchy of models can help in this regard.
Climate change research topics identified for immediate action
• Thorough understanding of the physics and dynamics of the Greenland and Antarctic ice sheets, with a view to predicting sea level rise within 20% for a specified change in climate over the ice sheets.
• Simulation of the main modes of variability in each of the main oceans (e.g. ENSO and PDO in the Pacific, thermohaline circulation (THC), meridional overturning circulation (MOC) and AMO in the Atlantic, and monsoons in the Indian Ocean) is essential. Replicating relative changes over the past 50 years is essential and is an initial value problem for the oceans.
• Re-evaluation of the projections for sea-level rise, aiming for a consensus rather than a lot of publications criticizing the Fourth Assessment Report.
• Establishing the likelihood of Amazon die-back – carbon dioxide source instead of sink.
• Links between land use/cover change and greenhouse gas emissions.
• Bringing the carbon cycle models to a level comparable with the physical climate change models and fully incorporating them.
• Reducing climate sensitivity.
• Tackling the resolution problem properly (not easy!).
International organization issues, especially regarding the IPCC
• The IPCC was designed 20 years ago when the problem was less well-understood and political acceptance more fragile. We now need to focus more on solutions. Future IPCC reports must be more focused, shorter and timely. We absolutely need a complete re-think.
• The Fourth Assessment Report is rather weak at including the latest research and thereby is losing credibility in the science community. During the whole process it loses actuality [timeliness].
• Construct the Fifth Assessment Report on the Synthesis model, rather than the three separate disciplines in the Working Group model – it has had its run in my view – incredibly valuable but becoming a bit repetitive and may have little original to say other than “we told you so last time and mean it even more now!”. This way people with very different understandings of science and policy problems and with very different world views would have time to work together to fashion real progress on interdisciplinary, policy-oriented questions from governments. The current Synthesis Report (SYR) is already very late in the game for such integrative understanding and thus is a difficult venue to accomplish interdisciplinary integration in the allotted time.
• Working Groups (WG) I and II ought to be rethought and perhaps combined with a different approach. WG III is involved in mitigation and is somewhat more separable except where effects of mitigation are sought and climate models have to be run to assess effects of “what if” scenarios.
• WGII is easily the weakest of the three reports. The reasons seem to be two-fold: (i) poor downscaling and (ii) the lack of a coherent methodology for impact study.
• Maintain ongoing interactions across the communities that populate the disciplinary working groups – like the core writing team of the Synthesis report at the moment – post-IPCC with a bit less stress to make a report and more time to learn from each other how to do integrative research to answer key questions like those posed above.
• Special reports on ice sheets and on the climate carbon-cycle feedback should be planned in 2-3 years, if not by IPCC then by someone else.
• Progress requires more attention to addressing basic model flaws. Without alleviating these, future IPCC assessments will look very similar each time. What a waste of resources…climate science will get what it deserves if it does not apply itself more to basics rather than what it is doing currently.
• Should have started the Synthesis Report team at least a year earlier while there was time for it to influence some of the Working Group reports.
Institutional/ infrastructure issues hamper climate change information delivery
• Problems identified, now we need to direct our science towards the “solutions”.
• There is a strong need to promote merging of IGBP and WCRP and revitalizing the international framework for climate science.
• There are too many committees and working groups and way too much time spent on liaising between ‘partners’.
• “Human-ware” is very much a depleted commodity, especially younger scientists having the urge and motivation to delve into climate problems. This rarely gets mentioned as a serious point.
• Simplify the international committee structure, reducing unnecessary overlap and complexity.
• Make the science of modelling more attractive to good young scientists. In part this requires less “publish or perish” management as model development is inevitably not a paper generator.
• More meetings to examine policy-driven questions with broader representations of disciplines, stakeholders and governments – not just to write and approve reports. • Better interaction between modelling and climatological communities.
• Essential to involve the social and economic sciences more – need reliable cost estimates, need to develop adaptation options etc.
• Strategies for mainstreaming climate change adaptation to (sustainable) development.
• Attention to the simulation of “weather” by climate models, thus accounting simultaneously for the verification of the so-called “fast” and “slow” time-scale processes.
• More generally, much more is needed in coming to grips with real prediction as an initial value problem.
It seems to me, even one year later, that the urgency and forthrightness of many of these comments still hold and need to be shared, discussed and acted upon. Those that concern me most include the simple, but dastardly, statement that “until and unless major oscillations in the Earth System can be predicted to the extent that they are predictable, regional climate is not a well defined problem. It may never be. The rush to emphasize regional climate does not have a scientifically sound basis.” This is underscored in another quote: “adding complexity to models, when some basic elements are not working right (e.g. the hydrological cycle) is not sound science.” (The italics are mine.)
There are other, more organizational but still very pertinent views such as: “future IPCC reports must be more focused, shorter and timely”; “human-ware is very much a depleted commodity”; and “the Fourth Assessment Report is rather weak at including the latest research and thereby is losing credibility in the science community.” Finally there is a cry from the heart – remember these quotes all come from IPCC lead authors, the guys at the coal face if we still dare cut coal – which says, “there are too many committees and working groups and way too much time spent talking!”
Did the final workshop outputs genuinely deliver these messages as clearly as they are stated here? Did we say “the IPCC was designed 20 years ago … we absolutely need a complete re-think” and “we need more time to learn from each other how to do integrative research to answer key questions”? My personal view is that we did not. Perhaps due to the natural desire to tone down criticism in written documents and perhaps because some of us wonder what else can be said – e.g. WGI is “becoming a bit repetitive and may have little original to say other than ‘we told you so last time and mean it even more now!’” Also there is real reluctance to state too baldly the magnitude of the challenges to be overcome before climate change research can deliver relevant results.
In some places there is an (unhealthy?) fear of mis- (or out of context) quoting by global warming “deniers”. We are hesitant to stress comments such as “the Fourth Assessment Report missed doing this owing essentially to the timelines that were arranged.” Another interesting example of this fear is that the original suggestion was to entitle the Sydney workshop, “What did the IPCC get wrong?” This proposal was quickly squashed in the corridors of the World Meteorological Organisation lest the anti-greenhouse lobby picked it up and repeated it as criticism of the IPCC.
Climate change research entered a new and different regime with the publication of the IPCC Fourth Assessment Report. There is no longer any question about “whether” human activities are changing the climate; instead research must tackle the urgent questions of: “how fast?”; “with what impacts?’; and “what responses are needed?” Climate change researchers cannot hide behind the need to improve models and observations any longer. Answers are now being demanded faster than, and at higher resolutions than, research can deliver.
It is clear that climate change will remain a risk management problem for the foreseeable future. However, the more we can constrain distribution functions of important process variables or outcomes like climate sensitivity or damages, the better will be humanity’s chances of adaptation. The cleverer we are in the design of relevant and deliverable climate change results, the sooner we constrain the potential for some really “dangerous” outcomes that cannot currently be ruled out at less than a 10% chance. One essential ingredient is transparency in communication. I hope that this article goes some way to ensure this.
• For those interested in finding out more, there are reports on the workshop in the reference list below (WMO, 2008 and Bojinski, S and Doherty S, 2008). And right now the final touches are being made to the full report of the responses – we hope it will be published next year (Doherty et al., 2009).
References
Bojinski, S., and Doherty S., 2008, Developing Strategies for Future Climate Change Science, Eos Trans. AGU, 89(11), 109
Doherty, S. J, Bojinski, S., Henderson-Sellers, A., Noone K., Goodrich, D., Bindoff, N. L., Church, J.,
Hibbard, K.A., Karl, T. R., Kajfez-Bogataj, L., Lynch, A.H., Mason, P.J., Parker, D.E., Prentice, C.,
Ramaswamy, V., Saunders, R.W., Simmons, A.J., Stafford Smith, M., Steffen, K., Stocker, T. F., Thorne, P. W., Trenberth, K., Verstraete, M.M., Zwiers, F.W., 2009, Lessons learned from IPCC: developments needed to understand and predict climate change for adaptation, 2008. Bulletin of American Meteorological Society, in press.
“IPCC Fourth Assessment Report”, 2007, The contents of the reports of Working Groups 1, 2 and 3 and the Synthesis report are accessible from http://www.ipcc.ch/
WMO, 2008, Future Climate Change Research and Observations: GCOS, WCRP and IGBP Learning from the IPCC Fourth Assessment Report, Workshop and Survey Report, GCOS-117, WCRP-127, IGBP Report No. 58, World Meteorological Organization, (WMO/TD No. 1418), January 2008, Geneva, 68pp, see here.
About the author
Ann Henderson-Sellers holds an Australian Research Council Professorial Fellowship in the Climate Risk CORE of Macquarie University. Until 2007 she was the Director of the World Climate Research Programme based in Geneva at the headquarters of the World Meteorological Organisation.”
There are quite interesting confessions within this essay! These include
The rush to emphasize regional climate does not have a scientifically sound basis
Until and unless major oscillations in the Earth System (El Nino-Southern Oscillation (ENSO), Pacific Decadal Oscillation (PDO), North Atlantic Oscillation (NAO) and Atlantic Multidecadal Oscillation (AMO) etc.) can be predicted to the extent that they are predictable, regional climate is not a well defined problem. It may never be. If that is the case then we should say so. It is not just the forecast but the confidence and uncertainty that are just as much a key.
Climate models need to be exercised for weather prediction; there are necessary but not sufficient things that can best be tested in this framework, which is just beginning to be exploited.
Energy budget is really worrisome; we should have had 20 years of ERBE [Earth Radiation Budget Experiment] type data by now- this would have told us about cloud feedback and climate sensitivity. I’m worried that we’ll never have a reliable long-term measurement. This combined with accurate ocean heat uptake data would really help constrain the big-picture climate change outcome, and then we can work on the details.
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October 1, 2008
The outstanding website Watts Up With That has weblogged (see) on an interesting new paper on the urban heat island;
Tamrazian, A., S. LaDochy, J. Willis, and W.C. Patzert, 2008: Heat Waves in Southern California: Are They Becoming More Frequent and Longer Lasting? APCG YEARBOOK, 70, 59-69, DOI: 10.1353/pcg.0.0001.
The abstract reads
“Los Angeles is experiencing more heat waves and also more extreme heat days. These numbers have increased by over 3 heat waves per century and nearly 23 days per century occurrences, respectively. Both have more than tripled over the past 100 years as a consequence of the steady warming of Los Angeles. Our research explores the daily maximum and minimum temperatures from 1906 to 2006 recorded by the Department of Water and Power (DWP) downtown station and Pierce College, a suburban valley location. The average annual maximum temperature in Los Angeles has warmed by 5.0°F (2.8°C), while the average annual minimum temperature has warmed by 4.2°F (2.3°C). The greatest rate of change was during the summer months for both maximum and minimum temperature, with late fall and early winter having the least rates of change. There was also an increase in heat wave duration. Heat waves lasting longer than six days occurred regularly after the 1970s but were nonexistent from the start of 1906 until 1956, when the first six-day heat wave was recorded. While heat days have increased dramatically in the past century, cold days, where minimum temperature is below 45°F (7.2°C), show a slight decreasing trend. Recent deadly heat waves in the western United States have generated increasing electricity demands. In light of the electricity response to recent extreme heat events, such as July 2006 heat waves in California, Missouri and New York, these results suggest the future increase in peak electricity demand will challenge current transmission and supply methods as well as future supply capacities when population and income growth are taken into account.”
Climate Science has weblogged on the urban heat island issue as it affects temperatures several times; e.g. see and see. There is an excellent paper on this subject also
Georgescu, M., G. Miguez-Macho, L. T. Steyaert, and C.P. Weaver, 2008: Sensitivity of summer climate to anthropogenic land cover change over the Greater Phoenix, AZ, Region, J. Arid Env., doi: 10.1016/j.jaridenv.2008.01.004.
What these studies show is that the societal risk to heat is much more significantly effected by the urbanization than from a possible change (e.g. +2C) in the global average surface temperature. Policy managers need to seek ways to reduce the risk from heat regardless of how the large scale climate is changing.
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September 30, 2008
There was a news article by Randolph E. Schmid (AP Science Writer) last Wednesday (September 24, 2008) which highlights another climate forcing [thanks to Ben Herman to alerting us to this news article].
The article is titled
“Study looks at beetles’ effects on weather”
The article starts with the text “Can a plague of beetles change the weather?” and proceeds to answer this question in the affirmative.
The article continues with the text
“Vegetation affects local weather by absorbing or reflecting sunlight and releasing chemicals and moisture. Changes can influence such things as rainfall, temperatures and smog…..’Forests help control the atmosphere, and there’s a big difference between the impacts of a living forest and a dead forest,’ NCAR scientist Alex Guenther, a principal investigator on the project, said in a statement. ‘With a dead forest, we may get different rainfall patterns, for example,’ he added……Indeed, preliminary computer modeling suggests that beetle kills of large forest areas can lead to temporary temperature increases of 2-to-4 degrees Fahrenheit, the researchers said.”
This news article is a useful summary of this local (and mesoscale) climate forcing. The only misimpression in the article is the statement that
”Living forests soak up carbon dioxide, while dead ones release it, potentially contributing to warming.”
Actually, while growing living forests (i.e. those increasing in biomass) can absorb more carbon than they emit during a year, dead trees from beetle kill may or may not release more carbon dioxide since it depends on whether the removal of the forest permits invigorated growth of new vegetation in the understory, as well as how rapidly the dead trees decompose.
Nevertheless, this is yet another example of the first order role of landscape change (both from natural and human management practices) on the climate system, that is summarized in
Pielke Sr., R.A., 2005: Land use and climate change. Science, 310, 1625-1626.
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September 29, 2008
We would like to thank Timo Hämeranta for alerting us to a new paper
Lean, Judith L., and David H. Rind, 2008. How natural and anthropogenic influences alter global and regional surface temperatures: 1889 to 2006. Geophys. Res. Lett., 35, L18701, doi:10.1029/2008GL034864.
The abstract reads
“To distinguish between simultaneous natural and anthropogenic impacts on surface temperature, regionally as well as globally, we perform a robust multivariate analysis using the best available estimates of each together with the observed surface temperature record from 1889 to 2006. The results enable us to compare, for the first time from observations, the geographical distributions of responses to individual influences consistent with their global impacts. We find a response to solar forcing quite different from that reported in several papers published recently in this journal, and zonally averaged responses to both natural and anthropogenic forcings that differ distinctly from those indicated by the Intergovernmental Panel on Climate Change, whose conclusions depended on model simulations. Anthropogenic warming estimated directly from the historical observations is more pronounced between 45°S and 50°N than at higher latitudes whereas the model-simulated trends have minimum values in the tropics and increase steadily from 30 to 70°N.”
In their Introduction, they write that
“Our results yield trends in the four individual global surface temperature components over the past 25, 50 and 100 years, augmenting the linear trends that IPCC reported in net global temperature for these same periods, and depicting the associated regional temperature trend patterns.”
There are several quite interesting statements in the article including
”Contrary to recent assessments based on theoretical models [IPCC, 2007] the anthropogenic warming estimated directly from the historical observations is more pronounced between 45°S and 50°N than at higher latitudes…”
“Climate models may therefore lack – or incorrectly parameterize - fundamental processes by which surface temperatures respond to radiative forcings.”
“ None of the natural processes can account for the overall warming trend in global surface temperatures. In the 100 years from 1905 to 2005, the temperature trends produce by all three natural influences are at least an order of magnitude smaller than the observed surface temperature trend reported by IPCC [2007].”
“In contrast with climate model simulations, the zonal surface temperature changes determined for natural (solar and volcanic) and anthropogenic influences from the historical surface temperature record do not increase rapidly from mid to high latitudes. Furthermore, since the temperature response to solar forcing occurs relatively rapidly (within months) with patterns that relate to existing tropospheric circulation patterns, the pathways likely involve dynamical motions not simply thermal processes that transfer heat to the deep ocean.”
The analysis presented in this paper provides an effective framework to seek to attribute reasons for long term climate trends. However, the use of the surface temperature data, with its range of uncertainties and biases; i.e. see
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
Lin, X., R.A. Pielke Sr., K.G. Hubbard, K.C. Crawford, M. A. Shafer, and T. Matsui, 2007: An examination of 1997-2007 surface layer temperature trends at two heights in Oklahoma. Geophys. Res. Letts., 34, L24705, doi:10.1029/2007GL031652.
is necessarily going to significantly alter their attribution study.
Climate Science recommends that a more robust study is for them to apply their analysis to the global average and regional pattern of tropospheric temperature variations and trends diagnosed in the UAH MSU and RSS MSU data, and in the upper ocean heat content data (see).
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September 28, 2008
The unusual snow and cold in South Africa that has occurred this week is reported as yet another example of global warming [thanks to Souleymane Fall for alerting us to this]; see
Warming has a hand in recent wild weather
where it is written
“The severe weather conditions experienced in South Africa in recent weeks are partially due to climate change.”
Additional articles on this weather event include Roads close after snowfalls and Snow hits South Africa. While clearly a single weather event does not inform us of what to expect in the future, the attribution of this cold and snow to global warming is yet another example of poor news reporting.
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September 25, 2008
UPDATE September 26 2008: I have requested that Dr. Ramanathan write an unedited guest reply to the Climate Science weblog below, but so far have not had a response. If he accepts my invitation, Climate Science will promptly publish on this website.
There is a new paper by a eminent and distinguished climate scientist, Dr. Ramanathan in the Proceedings of the National Academy of Sciences. [Thanks to David Douglass for alerting us to this new paper!]. The paper is
Ramanathan, V. and Y. Feng, 2008: On avoiding dangerous anthropogenic interference with the climate system: Formidable challenges ahead, PNAS, 105, 14245-14250, Sept 23, 2008.
with the abstract
“The observed increase in the concentration of greenhouse gases (GHGs) since the preindustrial era has most likely committed the world to a warming of 2.4°C (1.4°C to 4.3°C) above the preindustrial surface temperatures. The committed warming is inferred from the most recent Intergovernmental Panel on Climate Change (IPCC) estimates of the greenhouse forcing and climate sensitivity. The estimated warming of 2.4°C is the equilibrium warming above preindustrial temperatures that the world will observe even if GHG concentrations are held fixed at their 2005 concentration levels but without any other anthropogenic forcing such as the cooling effect of aerosols.The range of 1.4°C to 4.3°C in the committed warming overlaps and surpasses the currently perceived threshold range of 1°C to 3°C for dangerous anthropogenic interference with many of the climate-tipping elements such as the summer arctic sea ice, Himalayan–Tibetan glaciers, and the Greenland Ice Sheet. IPCC models suggest that ≈25% (0.6°C) of the committed warming has been realized as of now. About 90% or more of the rest of the committed warming of 1.6°C will unfold during the 21st century, determined by the rate of the unmasking of the aerosol cooling effect by air pollution abatement laws and by the rate of release of the GHGs-forcing stored in the oceans. The accompanying sea-level rise can continue for more than several centuries. Lastly, even the most aggressive CO2mitigation steps as envisioned now can only limit further additions to the committed warming, but not reduce the already committed GHGs warming of 2.4°C.”
I agree with Dr. Ramanthan that the addition of carbon dioxide into the atmosphere is a significant positive (warming) radiative forcing. Until the last few years, at least one of the global models (the GISS model projections) accurately simulated the long term upper ocean heat content; see
Comparison of Model and Observations Of Upper Ocean Heat Content.
Unfortunately, the Ramanthan and Feng PNAS paper does not use the more appropriate metric of ocean heat content changes as a diagnostic of global warming, but perpetuates a very significant misunderstanding of the Earth’s radiative fluxes by using the global average surface temperature anomaly.
When I served with Dr. Ramanthan on the 2005 National Research Council committee that produced the book
National Research Council, 2005: Radiative forcing of climate change: Expanding the concept and addressing uncertainties. Committee on Radiative Forcing Effects on Climate Change, Climate Research Committee, Board on Atmospheric Sciences and Climate, Division on Earth and Life Studies, The National Academies Press, Washington, D.C., 208 pp
we discussed the issue of “heat in the pipeline” and “unrealized heat” and I assumed we had come to an agreement on this. The term “committed warming“ is not used in the 2005 NRC report.
As has been discussed on Climate Science; see
Can The IPCC Model Projections Of Global Warming Be Evaluated From Just Several Years Of Data?
A Litmus Test For Global Warming - A Much Overdue Requirement
A Global Warming Currency
Pielke Sr., R.A., 2003: Heat storage within the Earth system. Bull. Amer. Meteor. Soc., 84, 331-335.
there is no “committed” heat in the climate system.
They are confusing the concept of “committed”heat with that of a non-equilibrium radiative imbalance.
What they are assuming is that the difference in the IPCC multi-decadal global model simulations from the radiatively unforced runs (i.e. no human-caused radiative forcing) and the radiatively forced runs is the “committed” heat and that this will continue into the future.
However, the IPCC models have not been shown to accurately predict the difference in incoming and outgoing radiative fluxes at the tropopause or surface in comparison with observed values of these fluxes.
This is why the ocean heat content changes are so useful as they provide a mechanism to diagnose this imbalance.
Dr. Ramanathan even agreed with this viewpoint in the 2005 National Research Council report which he co-authored. It is written on page 98 of that report
“The ocean is the largest heat reservoir in the climate system (Levitus et al., 2000, 2001). Thus, the change in ocean heat storage with time can be used to calculate the net radiative imbalance of the Earth (Ellis et al., 1978; Piexoto and Oort, 1992). In essence, the ocean heat content provides a metric for the integral in time of the TOA radiative forcing. Furthermore, it offers a valuable constraint on the performance of climate models (Barnett et al., 2001).”
In lieu of the more robust metric of global warming that is given by upper ocean heat content changes, the “global average surface temperature” concept (e.g. see Equation 1-1 on page 19 in NRC 2005) is used by Ramanathan and Feng despite their recognition of its limitations.
The Ramanthan and Feng paper is, therefore, misleading. There is no “unrealized heat” or “heat in the pipeline”. What they must show is that the radiative imbalances are persisting in the observations.
They misapply a concept that, while appropriate for a pot of water on the stove with a burner turned on to heat the pot, is too simplistic to apply to the climate system for the following reasons:
1. The simple pot analog that Ramathan uses implicitly assumes a static climate system in which the radiative forcing is nearly constant (the “unforced” condition in the multi-decadal global climate model simulations). This is clearly not true even on the annual time scale in which significant (over 30 Watts per meter squared) global average radiative imbalance occurs each year as a result of the different distance of the Earth from the Sun during the year; e.g. see
Ellis et al. 1978: The annual variation in the global heat balance of the Earth. J. Climate. 83, 1958-1962.
Ramanthan and Feng are basing their assumption on a long term nearly static radiative imbalance on models, not observations. This is a circular argument as the models are hypotheses only.
2. The use of the term global average surface temperature anomaly is misleading as, unlike a pot of water, the surface temperature anomaly is i) spatially varying (e.g. see), ii) its effect on the radiative imbalance is proportional to temperature to its fourth power (T**4), e.g. see, and iii) the surface is often not thermodynamically coupled to the rest of the climate system including the troposphere (e.g. see Section 2 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.
3. The recent studies
Spencer, R.W., and W.D. Braswell, 2008: Abstract- Feedback vs. Chaotic Radiative Forcing: “Smoking Gun” Evidence for an Insensitive Climate System? Download Powerpoint of presentation
Douglass, D.H., and J.R. Christy, 2008: Limits on CO2 Climate Forcing from Recent Temperature Data of Earth. Energy and Environment, accepted. [although not a standard journal, their analysis still needs to be responded to with respect to the Ramanathan and Feng paper]
as well as our analysis; see slide 27 in
http://www.climatesci.org/publications/presentations/PPT-101.pdf
have raised issues on the magnitude of the feedbacks, particularly atmospheric water vapor increases, but also snow and sea ice albedo decreases, which, according to the IPCC global models, are expected to amplify the positive radiative forcing of the well-mixed greenhouse gases, including carbon dioxide.
The dominant radiative feedback is supposed to be an increase in atmospheric water vapor, but, at most, this increase is muted; e.g. see
Climate Metric Reality Check #3 - Evidence For A Lack Of Water Vapor Feedback On The Regional Scale.
These feedbacks do not exist in a pot of water.
4. The statement by Ramanthan and Feng that “ IPCC models suggest that ≈25% (0.6°C) of the committed warming has been realized as of now” illustrates that they assume that the climate system has an equilibrium radiative balance, when in reality it does not. Moreover, they are using the IPCC models to evaluate how out-of-radiative-balance the climate system is, yet those models fail to adequately simulate the radiative feedbacks, nor even have all of the first order climate forcings. In the 2005 National Research Council report (on which Dr. Ramanathan was a co-author), it is written on page 100 that
“To date, all model projections of future climate have included a subset of climate forcings, typically greenhouse gas emission scenarios, solar variability, and more recently, aerosol emissions. As the diverse types of radiative and nonradiative climate forcings are recognized (e.g., aerosol indirect effects, changes in land cover), skillful projections of future global and regional climate will need to take them into account, an increasingly challenging task (Pielke Jr., 2001). Addressing this challenge may require a greater focus on assessing key societal and environmental vulnerabilities (Sarewitz et al., 2000).”
The recommendation that concludes the Ramanathan and Feng paper illustrates the inappropriate and societally negative consequences of their paper. They write at the end of their paper
”Decisionmakers have to consider the tradeoffs between air pollution abatement and GHGs mitigation steps but they urgently need predictive tools for making such trade-offs rationally, informed fully of the consequences of policy actions, e.g., future climate changes caused by switching of fuel types, including switching to ethanol, bio diesel and other bio fuels; reducing SO2 emission without warming-offsetting emission reductions in black carbon, NOx, and CO2.”
This “tradeoff” is an seriously misleading recommendation. There are no tradeoffs with respect to air pollution abatement! Health benefits of reducing air pollution should be a worldwide goal irrespective of how it alters the global average radiative forcing.
Thus, the Ramanthan and Feng paper is misleading in both the science of the climate system and in its policy consequences. The science issues can be summarized as:
- Their model of climate change (including global warming) using a single temperature global averaged anomaly is inadequate to properly diagnose global warming,
- the actual radiative feedbacks, based on observations, are more muted than simulated by the IPCC models, and
- the climate system is not in radiative balance at any time.
My challenge to the authors of the PNAS report is the following. Tell us what accumulation in Joules you expect, based on the IPCC models, for the last five year, and for each of the next ten years. How much more would the accumulation of Joules be without the negative radiative forcing of the aerosols? What is the spatial pattern of the changes in upper ocean heat content in Joules with time?
This then provides the benchmark with which we can compare to observations of ocean heat content changes in order to track what the authors claim is “committed” heating.
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September 24, 2008
Dr. Rene McPherson of the University of Oklahoma has contributed significantly to documenting the role of landscape processes as a first order climate forcing. This weblog is intended to provide much deserved recognition to her very important research on this subject.
In 2004, for example, she published an influential paper on the role of land management on the climate. The paper is
McPherson, R. A., D. J. Stensrud, and K. C. Crawford, 2004: The impact of Oklahoma’s wheat belt on the mesoscale environment. Mon. Wea. Rev., 132, 405–421.
The absract reads
“Oklahoma Mesonet data were used to measure the impact of Oklahoma’s winter wheat belt on the mesoscale environment from 1994 to 2001. Statistical analyses of monthly means of near-surface air temperatures demonstrated that 1) a well-defined cool anomaly existed across the wheat belt during November, December, January, February, and April, and 2) a well-defined warm anomaly existed across the wheat belt during June, July, and August. Data from crop year 2000 indicated a slight moist anomaly over the growing wheat from November 1999 through April 2000. In addition, based upon 21 000 daily statistics over eight unique years, statistical computations indicated less than a 0.1% chance that the moist anomaly during March resulted from random chance.
During the period from 1999 to 2001, about 50 days between 15 March and 1 May showed evidence of heightened values of daily maximum dewpoint over Oklahoma’s winter wheat belt as compared to adjacent grasslands. On more than half of these days, the dewpoint was enhanced only across five or six counties in north-central Oklahoma, where the winter wheat production was the largest. Another 90 days between 1 June and 31 July revealed a distinct warm anomaly in daily maximum air temperatures over the wheat belt, particularly across north-central Oklahoma.
These analyses demonstrate that Oklahoma’s winter wheat belt has a dramatic impact on the near-surface, mesoscale environment during its growth and after its harvest. Consequently, it is imperative that mesoscale forecasts, whether produced objectively or subjectively, account for the vegetation–air interactions that occur across western Oklahoma and, presumably, across other crop regions in the United States and around the globe.”
Additional publications from this well qualified climate scientist can be found on her website http://csa.ou.edu/person.php?id=18.
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September 23, 2008
Climate Science has promoted the perspective that climate forcings involve much more than just the radiative forcing from carbon dioxide. This viewpoint is also emphasized in a National Research Council report
National Research Council, 2005: Radiative forcing of climate change: Expanding the concept and addressing uncertainties. Committee on Radiative Forcing Effects on Climate Change, Climate Research Committee, Board on Atmospheric Sciences and Climate, Division on Earth and Life Studies, The National Academies Press, Washington, D.C., 208 pp.
There was a paper in 2006 that investigated one of these issues; the role of mineral aerosols as a climate forcing. The paper is
Mahowald N. M., M. Yoshioka, W. D. Collins, A. J. Conley, D. W. Fillmore, D. B. Coleman (2006), Climate response and radiative forcing from mineral aerosols during the last glacial maximum, pre-industrial, current and doubled-carbon dioxide climates, Geophys. Res. Lett., 33, L20705, doi:10.1029/2006GL026126.
The abstract reads
“Mineral aerosol impacts on climate through radiative forcing by natural dust sources are examined in the current, last glacial maximum, pre-industrial and doubled-carbon dioxide climate. Modeled globally averaged dust loadings change by +88%, +31% and −60% in the last glacial maximum, pre-industrial and future climates, respectively, relative to the current climate. Model results show globally averaged dust radiative forcing at the top of atmosphere is −1.0, −0.4 and +0.14 W/m2 for the last glacial maximum, pre-industrial and doubled-carbon dioxide climates, respectively, relative to the current climate. Globally averaged surface temperature changed by −0.85, −0.22, and +0.06 °C relative to the current climate in the last glacial maximum, pre-industrial and doubled carbon dioxide climates, respectively, due solely to the dust radiative forcing changes simulated here. These simulations only include natural dust source response to climate change, and neglect possible impacts by human land and water use.”
In the conclusions, they write
“The net instantaneous top-of-atmosphere radiative forcing differences due to dust between the last glacial maximum, pre-industrial and doubled-carbon dioxide climates and the current climate are −0.53, −0.43, and +0.14 W/m2, respectively. If we include the impact of glaciogenic sources, the net top-of-atmosphere radiative forcing difference between the last glacial maximum and the current climate increases in magnitude to −1.04 W/m2. In the future we simulate a 0.14 W/m2 increase in radiative forcing because of a reduction in dust from carbon dioxide fertilization of the vegetation. It is uncertain that the carbon dioxide fertilization effect will continue in the future, when other nutrients may become limiting….”
and
“ Despite the possible sensitivity of the results to our model specifications, our results suggest some interesting relationships across the different climate studies. Radiative forcing at the top-of-atmosphere and surface is linear with aerosol optical depth, even in different climates. Climate response in surface temperature and precipitation are roughly linear with aerosol optical depth in our model, with a decrease in both surface temperature and precipitation associated with increasing optical depth. Finally, our model predicts statistically significant decreases in temperature at many latitudes (not just close to the dust sources) when dust is added in the different climates, and a shift in precipitation from the northern part of the ITCZ to the southern part of the ITCZ.”
Mineral dust is yet another climate forcing that was inadequately assessed in the 2007 IPCC report. Mineral dust has a natural component (it occurred prior to any human disturbance of the landscape), and now has a human contribution through landscape degradation as a result of deliberate and inadvertent land management practices.
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Weblog editor: Dallas Staley (dallas AT cires DOT colorado DOT edu)
