Comments on a New Report on Climate Change in Colorado: A Synthesis to Support Water Resources Management and Adaptation for the Colorado Water Conservation Board by Ray et al. 2008

Recently a report titled

“Climate Change in Colorado:  A Synthesis to Support Water Resources Management and Adaptation for the Colorado Water Conservation Board” by Andrea J. Ray, Joseph J. Barsugli, Kristen B. Averyt, Martin Hoerling, and Klaus Wolter

was released. The report has valuable information on the climate of Colorado and is written by well-respected climate scientists.

However, the Report is has serious flaws in providing guidance to policymakers on dealing with water resource issues in Colorado in the coming decades. Three of the major deficiencies in the report can be summarized as follows.

1.  Use Of The IPCC Models To Predict Colorado Climate Out To 2050.

The statement in the Report that

“Climate models project Colorado will warm by 2°F by 2025, and 4°F by 2050. The projections show summers warming more (+5°F) than winters (+3°F), and suggest that typical summer temperatures in 2050 will be as warm as or warmer than the hottest 10% of summers that occurred between 1950 and 1999. By 2050, temperatures on the Eastern Plains of Colorado will shift westward and upslope, bringing into the Front Range temperature regimes that today occur near the Kansas border.”

is just a hypothesis based on global models that do not have all of the first-order human climate forcings, as well as all of the important climate feedbacks. There is no skill at regional forecasts decades into the future.

There have been a variety of statements and papers that emphasize that the IPCC multi-decadal climate models have no regional skill (even when downscaled). For example, one of the IPCC Lead Authors, Kevin Trenberth, in a candid weblog [; see also],  stated

“None of the models used by IPCC are initialized to the observed state and none of the climate states in the models correspond even remotely to the current observed climate.”

“I [Kevin Trenberth] postulate that regional climate change is impossible to deal with properly unless the models are initialized.”

“….the science is not done because we do not have reliable or regional predictions of climate.”

A recent example of a peer-reviewed paper that documents the inability of the IPCC models to skillfully predict regional climate is

Koutsoyiannis, D., A. Efstratiadis, N. Mamassis, and A. Christofides, 2008: On the credibility of climate predictions, Hydrological Sciences Journal, 53 (4), 671-684

Where they write

“Geographically distributed predictions of future climate, obtained through climate models, are widely used in hydrology and many other disciplines, typically without assessing their reliability. Here we compare the output of various models to temperature and precipitation observations from eight stations with long (over 100 years) records from around the globe. The results show that models perform poorly, even at a climatic (30-year) scale. Thus local model projections cannot be credible, whereas a common argument that models can perform better at larger spatial scales is unsupported.”
“At the annual and the climatic (30-year) scales, GCM interpolated series are irrelevant to reality……future climate projections at the examined locations not credible. Whether or not this conclusion extends to other locations requires expansion of the study, which we have planned. However, the poor GCM performance in all eight locations examined in this study allows little hope, if any. An argument that the poor performance applies merely to the point basis of our comparison, whereas aggregation at large spatial scales would show that GCM outputs are credible, is an unproved conjecture and, in our opinion, a false one.”
The claim to be able to skillfully project Colorado climate out to 2050 is scientifically invalid and will mislead policymakers. There is no skill in multi-decadal regional climate predictions for Colorado.
2.   The reliance of the Colorado report on the 2007 IPCC and CCSP Reports, which attribute recent climate change to primarily the “thickening blanket of greenhouse gases (including carbon dioxide)” , is scientifically flawed.
The failure of the IPCC and CCSP reports to adequately assess the state of climate science is summarized in Comments On The Draft CCSP Report “Global Climate Change Impacts in the United States” []

Where I wrote

“This Draft CCSP report failed to adequately report on the understanding of the role of humans within the climate system by the climate science community. As just one example, the statement is made in the text that

“Human-induced climate change and its impacts are apparent now throughout the United States. Global warming is unequivocal and is due primarily to human-induced emissions of heat-trapping gases and other pollutants.”

This claim is inconsistent with the conclusions in the 2005 NRC report that there are other first-order human climate forcings;

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 concluded 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…Regional diabatic heating can also cause atmospheric teleconnections that influence regional climate thousands of kilometers away from the point of forcing. Improving societally relevant projections of regional climate impacts will require a better understanding of the magnitudes of regional forcings and the associated climate responses.” [page 5 of the 2005 NRC report]


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. Aerosols exert a forcing on the hydrological cycle by modifying cloud condensation nuclei, ice nuclei, precipitation efficiency, and the ratio between solar direct and diffuse radiation received. Other nonradiative forcings modify the biological components of the climate system by changing the fluxes of trace gases and heat between vegetation, soils, and the atmosphere and by modifying the amount and types of vegetation…..Nonradiative forcings have eventual radiative impacts, so one option would be to quantify these radiative impacts. However, this approach may not convey appropriately the impacts of nonradiative forcings on societally relevant climate variables such as precipitation or ecosystem function. Any new metrics must also be able to characterize the regional structure in nonradiative forcing and climate response.” [page 6 of the 2005 NRC report].

Thus, the scientific evidence presented in the 2005 NRC report supports the perspective that

The human influence on the climate system is significant and involves a diverse range of first-order climate forcings, including, but not limited to the human input of CO2

The failure of the IPCC and CCSP process to accurately communicate the current understanding of climate science is also summarized in

Pielke Sr., Roger A., 2008: A Broader View of the Role of Humans in the Climate System is Required In the Assessment of Costs and Benefits of Effective Climate Policy. Written Testimony for the Subcommittee on Energy and Air Quality of the Committee on Energy and Commerce Hearing “Climate Change: Costs of Inaction” – Honorable Rick Boucher, Chairman. June 26, 2008, Washington, DC., 52 pp

 where the oral statement reads, in part,

“The human addition of CO2 into the atmosphere is a first-order climate forcing. We need an effective policy to limit the atmospheric concentration of this gas. However, humans are significantly altering the climate system in a diverse range of ways in addition to CO2. The information that I am presenting will assist in properly placing CO2 policies into the broader context of climate policy.
Climate is much more than just long-term weather statistics but includes all physical, chemical, and biological components of the atmosphere, oceans, land surface, and glacier-covered areas. In 2005, the National Research Council published a report “Radiative forcing of climate change: Expanding the concept and addressing uncertainties” that documented that a human disturbance of any component of the climate system, necessarily alters other aspects of the climate……
Thus climate policy that is designed to mitigate the human impact on regional climate by focusing only on the emissions of CO2is seriously incomplete unless these other first-order human climate forcings are included, or complementary policies for these other human climate forcings are developed. Moreover, it is important to recognize that climate policy and energy policy, while having overlaps, are distinctly different topics with different mitigation and adaptation options.
A way forward with respect to a more effective climate policy is to focus on the assessment of adaptation and mitigation strategies that reduce vulnerability of important societal and environmental resources to both natural and human caused climate variability and change. For example, restricting development in flood plains or in hurricane storm surge coastal locations is an effective adaptation strategy regardless of how climate changes.

In conclusion, humans are significantly altering the global climate, but in a variety of diverse ways beyond the radiative effect of carbon dioxide. The CCSP assessments have been too conservative in recognizing the importance of these human climate forcings as they alter regional and global climate. These assessments have also not communicated the inability of the models to accurately forecast future regional climate on multi-decadal time scales since these other first-order human climate forcings are excluded. The forecasts, therefore, do not provide skill in quantifying the impact of different mitigation strategies on the actual climate response that would occur as a result of policy intervention with respect to only CO2.”

Thus the basic foundation of the Colorado report on the attribution of the dominate reason for climate change to be “the thickening blanket of greenhouse gases (including carbon dioxide)” is scientifically invalid.

3.   In documenting recent changes in Colorado climate, the report was incomplete in presenting peer-reviewed research which presents a more complex pattern of variability and change.

These papers include

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

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

 [this paper is included in the report, but its major findings are not].

Davey, C.A., and R.A. Pielke Sr., 2005: Microclimate exposures of surface-based weather stations – implications for the assessment of long-term temperature trends. Bull. Amer. Meteor. Soc., Vol. 86, No. 4, 497-504.

Pielke Sr., R.A., C. Davey, and J. Morgan, 2004: Assessing “global warming” with surface heat content. Eos, 85, No. 21, 210-211.

Hanamean, J.R. Jr., R.A. Pielke Sr., C.L. Castro, D.S. Ojima, B.C. Reed, and Z. Gao, 2003: Vegetation impacts on maximum and minimum temperatures in northeast Colorado. Meteorological Applications, 10, 203-215.

Pielke Sr., R.A., and T. Matsui, 2005: Should light wind and windy nights have the same temperature trends at individual levels even if the boundary layer averaged heat content change is the same? Geophys. Res. Letts., 32, No. 21, L21813, 10.1029/2005GL024407.

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.

Fall, S., D. Niyogi, R.A. Pielke Sr., A. Gluhovsky, and E. Kalnay, 2008: Impacts of land surface properties on temperature trends using North American regional reanalysis over the USA. Int. J. Climatol., in revision.

Pielke Sr., R.A., N. Doesken, O. Bliss, T. Green, C. Chaffin, J.D. Salas, C. Woodhouse, J.L. Lukas, and K. Wolter, 2005: Drought 2002 in Colorado – An unprecedented drought or a routine drought? Pure Appl. Geophys., Special Issue in honor of Prof. Singh, 162, 1455-1479, doi:10.1007/200024-005-2679-6.

Pielke, R.A. Sr., K. Wolter, O. Bliss, N. Doesken, and B. McNoldy, 2006: The July 2005 Denver heat wave: How unusual was it? Nat. Wea. Dig., 31, 24-35. 

In the Pielke et al. (2002) paper, for example, we evaluated long-term trends in average maximum and minimum temperatures, threshold temperatures, and growing season in eastern Colorado and found a wide variety of trends. Davey and Pielke (2005) photographically documented the poor siting exposures of the sites used to examine long-term temperature trends [and this photographic documentation should be a required part of the current report for each of the stations listed in this report].

Pielke et al. (2004) showed that unless the trends in dewpoint temperature are measured at the same times as the dry bulb temperature, the attribution of temperature changes to large-scale atmospheric, rather than to surface landscape changes, could be erroneous. Pielke and Matsui (2005) and Lin et al. (2007) show that the use of the minimum temperature, measured at just one level, results in a significant warm bias if the overall boundary layer were warming (e.g., due to cloud cover changes, land-use change, as well as local increased atmospheric concentrations of CO2 and/or water vapor). In the global long-term temperature record, about 30% of the reported warming, that has been reported by the IPCC can be explained by this one warm bias.

The report ignored research studies in Colorado which present a more complex variation of regional climate during the last several decades, as well as document a diversity of reasons for these variations.


With respect to the report on trends and variability of temperature and precipitation in Colorado in the past, the report should have included the information that they did provide, but it needs also to be inclusive of all the available studies that present a more complex pattern of trends.

The summary of the data should not use the IPCC models to attribute the trends to primarily human-induced emissions of heat-trapping gases and other pollutants, nor to provide regional forecasts to policymakers. The authors of the report are just repeating the claims in the IPCC and CCSP reports which have been shown to be seriously incomplete.

I had recommended in my reviews of the report that they delete the section on the projection of the climate for Colorado for the coming decades, and replace with the vulnerability framework reported on in Chapter E in

Kabat, P., Claussen, M., Dirmeyer, P.A., J.H.C. Gash, L. Bravo de Guenni, M. Meybeck, R.A. Pielke Sr., C.J. Vorosmarty, R.W.A. Hutjes, and S. Lutkemeier, Editors, 2004: Vegetation, water, humans and the climate: A new perspective on an interactive system. Springer, Berlin, Global Change – The IGBP Series, 566 pp.

and in

Pielke Sr., R.A., J.O. Adegoke, T.N. Chase, C.H. Marshall, T. Matsui, and D. Niyogi, 2007: A new paradigm for assessing the role of agriculture in the climate system and in climate change. Agric. Forest Meteor., Special Issue, 132, 234-254. 

These papers provide a more complete assessment tool for the threats that water resources face in Colorado from the spectrum of human and natural climate and other environmental and social variations and change.

I was pleased to see, while the authors did not delete the regional projections, they did  include a short section on a bottom-up vulnerability perspective in on page 42 and Figure 6.1, in response to my comments, but they still insisted on including model projections; i.e. in Sidebar 3-2 they wrote

“Average monthly GCM changes in temperature and precipitation for 2030 and 2070 were combined with multiple recreations of the paleoclimate record to simulate the combined effects of changes in climate and paleoclimate variability.”

They also did not highlight this type of vulnerability assessment in the Executive Summary.

For example, as seen in the tree ring proxy data of precipitation in Figure 2-9 in the Report (and also see, Colorado is at major risk to climate variations and change, regardless of how humans are altering the climate system. This assessment of vulnerability to water resources, using historical, paleo-record, and selected worst-case drought scenarios (i.e., driest sequences of years) should be the focus for threats Colorado might face in the coming decades to our water supply. The use of the IPCC and CCSP reports as the basis for a very limited range of climate scenarios eliminates, for example, an assessment of the consequences if actual past drought conditions reoccured in the coming decades, but with the human demands on water that will be faced in this time period.

This issue was also weblogged on October 27 2008 in the posting

New Article On The Need To Move From Dubious Multi-Decadal Regional Climate Predictions To The Assessment of Regional Vulnerabilites.

Finally, if one or more of the authors of the report would like to write a guest weblog on this issue for Climate Science, they are invited to do so.



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