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Global climate models are accurate enough to be relied upon

My opponent's quotes: In the previous round, my opponent presented several quotes from experts who seemed to believe that models are not accurate enough to be relied upon. However, many of these quotes were taken from seriously flawed studies or biased sources. For instance, let’s consider his second quote which came from a scientific paper published by Douglass, Christy, Pearson, and Singer in late 2007. This paper purported to demonstrate that modeled and observed tropical temperature trends disagree to a statistically significant extent. However, other scientists have identified major flaws in this study. As Dr. Ben Santer and his colleagues stated, “The author’s conclusions were based on the application of a flawed statistical test and the use of older observational datasets.” (1) Once these errors were corrected, Dr. Santer found that model simulations matched the observations very closely. Let’s also examine my opponent’s third quote which came from an expert affiliated with the National Center for Policy Analysis. Interestingly, this conservative think tank has received thousands of dollars in funding from ExxonMobil and the Koch Industries. (2-3) As extensive research has shown, the conclusions of a scientific study usually support the interests of the study's financial sponsor. (4-5) Therefore, the quote my opponent provided should not be weighted heavily. Hansen’s projections: My opponent claims that I compared Hansen’s projections to only land temperature data. However, if my opponent had examined my sixth reference, he would realize that this is not the case. In reality, I compared the model projections to the GISS land-ocean temperature index, which includes data from all over the globe. My opponent also alleges that I compared the temperature data to model projections for Hansen’s “C” scenario. However, as I explained very clearly, I actually compared the data to the more realistic “B” scenario. Clearly, I was not "cherry-picking" data, as my opponent alleges. Dessler’s findings: My opponent claims that Dessler’s findings have been refuted by a study conducted by Roy Spencer. However, this is not the case. Spencer’s study was published nearly four years ago, while Dessler’s study was just released six months ago. Moreover, Spencer analyzed only five years of satellite data while Dessler considered an entire decade of observations. Spencer himself has even stated that,"The time scales addressed here are short and not necessarily indicative of climate time scales". Thus, we can be virtually certain that Dessler’s results are much more robust than Spencer’s. Dessler's conclusions are also supported by a variety of studies showing that Lindzen’s IRIS hypothesis is incorrect. (6-8) As Lin et al. stated, “The observations show that the clouds have much higher albedos and moderately larger longwave fluxes than those assumed by Lindzen et al. As a result, decreases in these clouds would cause a significant but weak positive feedback to the climate system, instead of providing a strong negative feedback.” (6) Upper Tropospheric warming: My opponent claims that the troposphere is not warming as rapidly as models predict. He cites two studies to back up this claim, both of which were published over four years ago. Obviously, new satellite and radiosonde datasets have been developed since the publication of these studies. These new datasets show enhanced tropospheric warming due to improvements in our ability to identify and adjust for biases introduced by changes over time in the instruments used to measure temperature. (1) As one study concluded, two newly adjusted radiosonde time series indicate that the upper troposphere is warming at a rate of .2–.3ºC per decade. This is almost exactly what the models have predicted. (9) Other independent observations also indicate that the upper troposphere is warming at a rate consistent with models. For example, one study used measurements of wind shear to estimate temperature trends. This study concluded as follows: “We derive estimates of temperature trends for the upper troposphere to the lower stratosphere since 1970. Over the period of observations, we find a maximum warming trend of 0.65º K per decade near the 200 hPa pressure level, below the tropical tropopause. Warming patterns are consistent with model predictions except for small discrepancies close to the tropopause. The agreement with models increases confidence in current model-based predictions of future climate change.” (10) In summary, the discrepancies that my opponent pointed out were most likely due to inaccuracies in the old observational datasets, not fundamental model errors. This is just another example demonstrating that models can actually be more accurate than data. Response to the Mount Pinatubo eruption: When Mount Pinatubo erupted in 1991, it provided a meaningful opportunity to evaluate how accurately models could predict the climate response to an increase in sulfate aerosols. The models accurately forecasted the subsequent global cooling of about 0.5°C soon after the eruption. Furthermore, the radiative, water vapor and dynamical feedbacks included in the models were verified. (11) Simulations of the planet’s energy imbalance: Global climate models have accurately simulated the planetary energy imbalance. As Dr. James Hansen concluded, “Our climate model...calculates that Earth is now absorbing 0.85 watts per square meter more energy from the Sun than it is emitting to space. This imbalance is confirmed by precise measurements of increasing ocean heat content over the past 10 years.” (12) Conclusion: As the Intergovernmental Panel on Climate Change concluded, “There is considerable confidence that climate models provide credible quantitative estimates of future climate change, particularly at continental scales and above. This confidence comes from the foundation of the models in accepted physical principles and from their ability to reproduce observed features of current climate and past climate changes. Over several decades of development, models have consistently provided a robust and unambiguous picture of significant climate warming in response to increasing greenhouse gases.” (13). References: http://www.realclimate.org... http://www.guardian.co.uk... http://www.greenpeace.org... http://www.bmj.com... http://onlinelibrary.wiley.com... http://journals.ametsoc.org... http://www.atmos-chem-phys-discuss.net... http://journals.ametsoc.org... http://journals.ametsoc.org... http://www.nature.com... http://pubs.giss.nasa.gov... http://pubs.giss.nasa.gov... http://ipcc.ch...