Global Warming Science -




[last update: 2009/12/28]



Several Brigham Young University Earth Scientists sent an “Open letter to the Utah Public Utilities and Technology Interim Committee, Governor, U.S. Senators and Congressmen” professing a belief in the standard human caused CO2-based global warming scenario, stating:

Utah may sustain serious damage due to a warming climate”.


The Salt Lake Tribune reported the letter here: []

The letter is available here: []


This document briefly examines Utah’s “warming climate” and the effects.





Any examination of historical climatic trends should be made in the context of the IPCC presumptions.


In a CRU email between Edward Cook and Michael Mann in May 2001, Cook stated: “most researchers in global change research would agree that the emergence of a clear greenhouse forcing signal has really only occurred since after 1970. I am not debating this point, although I do think that there still exists a significant uncertainty as to the relative contributions of natural and greenhouse forcing to warming during the past 20-30 years at least.” []


The figure below left shows the global average temperature anomalies (from the Hadley Climatic Research Unit (CRU) which provides the data used by the IPCC []).


The figure below right superimposes the CRU temperature anomalies on the IPCC graph of model outputs. (IPCC 2007 AR4 Figure SPM-4 []) In this figure, the blue shaded bands show the result climate model simulations using only natural forcings. Red shaded bands show the result model simulations including anthropogenic CO2. 



This clearly shows that prior to about 1973, the global warming is fully explained by climate models using only natural forcings (i.e. no human CO2). The models need input of CO2 only after about the mid-1970s – prior to 1970 all warming was natural, according to the IPCC.


The BYU scientists’ letter states: “it was claimed that the Intergovernmental Panel on Climate Change (IPCC) ignored the possibility that natural climate cycles are responsible for most of the climate change evident over the past century. This is patently false.” This statement of theirs is itself false. The IPCC attributes “most” of the warming since 1970 to human-produced (anthropogenic) greenhouse gases – mainly CO2. One must keep in mind that the IPCC was formed in 1988 with the purpose of assessing “the understanding of the risk of human-induced climate change.”  -- i.e. it is based on the a priori assumption of “human-induced climate change” – there was never an attempt to evaluate the scientific evidence of the cause. (See: for the history).




Temperatures and PDO


The BYU scientists’ “open letter” implies that the Pacific Decadal Oscillation (PDO) is not related to Utah’s climate. Although they do not directly state that, they say: “it was claimed that climate scientists have ignored the hypothesis that the Pacific Decadal Oscillation, a natural mode of climate variability, could be responsible for climate change over the last century. The inaccuracy of this claim can also be readily demonstrated. A database search on our university library system, prompted by this claim, uncovered more than 600 peer-reviewed, scientific articles addressing the relationship of the Pacific Decadal Oscillation with climate change on many timescales, published within just the last five years alone.” They don’t state what is in the 600 articles, so we’ll take a look at the actual data.


The following figure shows the annual average temperature anomalies for the two 5x5 degree grids covering most of Utah. This is from the Hadley Climatic Research Unit (HadCRU) CRUTEM3 database used by the IPCC (plotted at The warmest year (as for the United States as a whole) was 1934.



The following figure shows the average of the above two 5x5 degree grids.




The following figure shows the Pacific Decadal Oscillation (PDO) (from




The following figure shows the average annual temperature anomalies for the averaged two 5x5 degree grids shown above, changed to green and superimposed on the PDO. The relationship between the PDO and Utah temperature cannot be denied.



It is clear that the current warming in Utah is not unprecedented and not statistically significant. It is also clear that the Utah temperatures are related to the PDO.


The following figures show the annual average temperatures for a couple of stations in Utah from the NASA GISS temperature database []. Current warming is similar to the 1930s, when the IPCC says it was natural.








The following figure shows the total annual precipitation for Utah (from the National Climatic Data Center 



It is clear that Utah’s rainfall in recent decades is not out of the normal range and the long-term trend is increasing total rainfall.





The BYU scientists’ letter states: “We, the undersigned scientists, agree with the consensus view - that climate is changing and is significantly influenced by human activity. … We encourage our legislators not to manipulate the scientific evidence to suit any political agenda.


I completely agree with the last statement – legislators should not manipulate scientific evidence. However, it seems the scientists themselves are trying to mislead the Utah legislators – there has been no warming or decrease in precipitation in Utah and contrary to their implications, the PDO is the dominant climate driver in Utah.


Their statement: “Utah’s climate scientists are a valuable resource to help public officials decide how to respond to the threat” is facetious – they are misleading the public officials about the role of the PDO.


Their statement: “Utah may sustain serious damage due to a warming climate” is pure politics, lacking any scientific basis.