By far the three most prominent and most frequently referenced climate scientists who are "skeptical" of the dangers of human-caused global warming are Dr Richard Lindzen of MIT, and Drs. Roy Spencer and John Christy of the University of Alabama at Huntsville (UAH). These are not your typical unqualified "skeptics", like so many others (i.e. computer programmers, politicians, and former political consultants). No, these are genuine climate scientists who receive government research grants, publish peer-reviewed studies, and have not received any funding from fossil fuel companies in recent years. Thus their arguments are well worth examining. Is there scientific validity to their skepticism?This question is of particular importance since they have recently received so much media attention. Dr. John Christy, for example, has recently tesitfied before US Congress, appeared on an Australian radio talk show, and on a Canadian radio show. In these appearances, he advised his audiences that there is a great deal of uncertainty regarding man-made global warming, and that we need not take significant steps to reduce human greenhouse gas emissions. This advice directly contradicts the findings of the vast majority of Dr. Christy's peers, most recently by the Australian Climate Commission, which concluded that we know beyond a reasonable doubt that humans are the primary cause of the current global warming, and it is critical that we immediately implement policies to reduce global greenhouse gas emissions.
We recently examined the scientific arguments of Dr. Richard Lindzen, and found that his arguments do present a mostly consistent alternative to the man-made global warming theory. Essentially Dr. Lindzen argues that the climate is not very sensitive to increases in atmospheric greenhouse gases, and the warming we've observed is mainly due to the internal variability of the climate system. However, we also found that Dr Lindzen's alternative hypothesis is little more than a flimsy house of cards, with each scientifically faulty argument built upon several other faulty arguments. In fact every single one of his arguments has turned out to be inconsistent with the observational evidence. So what about Dr. Christy - does he present a consistent alternative hypothesis to the man-made global warming theory which is more scientifically accurate than Dr. Lindzen's?
No, as it turns out, we find that Dr. Christy's arguments create a similar, but less sophisticated alternative in comparison to Dr. Lindzen's. The foundation of Dr. Christy's arguments is that despite over four decades of climate science research, we still do not understand the workings of the global climate much better than we did in 1970, and that as a result, we are "jumping to conclusions" in blaming recent global warming on human activities. However, contrary to Dr. Christy's uncertainty exaggerations, the human influence on the recent global warming is one of the aspects which climate scientists are most certain about.
However, once he sows the seeds of doubt into the minds of his audience, Dr. Christy proceeds to argue, similar to Dr. Lindzen, that recent warming could simply be due to the internal variability of the global climate. Dr. Christy argues that this is a plausible alternative explanation to man-made global warming because "we", as he puts it, are finding that the climate is not sensitive to greenhouse gases, and he claims that observational data is not consistent with climate model predictions. Thus, Dr Christy concludes, reducing greenhouse gas emissions will have little impact on the climate.
As you can see, this is a very similar alternative hypothesis to that put forth by Dr. Lindzen. In fact, when Dr. Christy says "we" are finding that the climate is insensitive to greenhouse gases, he refers exclusively to studies by Dr Lindzen and Dr Spencer. Virtually all other climate science research has found that the climate is indeed quite sensitive to greenhouse gases, and the work of Dr Lindzen and Dr Spencer concluding otherwise contains numerous errors. And as with Dr. Lindzen's alternative hypothesis, every single one of Dr. Christy's arguments is directly contradicted by the observational data (as illustrated in the links above).
Thus unfortunately we once again find that even the arguments by climate scientist "skeptics" that we need not worry about global warming or greenhouse gas emissions are scientifically unsound. There's an important distinction to be made here: human-caused global warming is a robust scientific theory which is supported by a vast body of evidence and has withstood extreme scientific scrutiny for many decades. The alternative hypotheses like that of Dr. Christy, on the other hand, have quickly been falsified by ongoing scientific research.
Additionally, another critical point which Dr. Christy neglects is that even aside from climate change, our carbon emissions are also causing ocean acidification (another major environmental problem which we refer to as "global warming's evil twin"), and there are numerous other issues with our continued reliance on fossil fuels (i.e. peak oil, air pollution, reliance on foreign energy sources, etc.). It's unfortunate that Dr. Christy and his two "skeptic" colleagues continue to present this misleading and scientifically unsound information to the general public and policymakers, because the more we listen to them and the longer we wait, the worse the consequences will be.