Wood Romances

We hear a lot that climate models predict too much warming of global mean surface temperature (GMST), but just about every graph intended to back this up contains flaws or misrepresentations, either by sloppy comparisons of models vs observations or using a subset of models that are heavily influenced by those with high sensitivities. I think it's valuable to show how well models form, since the sensitivities of those that perform the best are likely to be good indicators of the sensitivity of the real climate system. So I thought I'd toss my hat in the ring by comparing Hansen's 1988 climate model with observations. This has been done before, most notably by Zeke Hausfather in 2019, but it's been 6 years since then, and I thought it might be good to update it. To do this, I downloaded Hansen's data for GHG forcings and temperatures for his Scenarios A, B and C (available here and here ), and I plotted these scenarios with the major GMST datasets against their 1958...

The graph below from John Shewchuk is intended to show that models predict too much warming compared to satellite data. Shewchuk claims that the red line is the average of 102 IPCC CMIP5 model runs for the surface through 50K feet. In all likelihood, this is just lifted from graphs of model-observation comparisons that John Christy has plotted in the past. Shewchuk claims the blue line is UAH satellite observations for the total troposphere layer (TTT). The problems with this graph are numerous, and many of the problems are inherited from Christy's graph (problems with his comparison are well-documented ). The two time series are separated from each other even in 1980 to exaggerate the differences between the two (even if the trendlines do intersect at 1980). The 102 model runs are not shown, only the model mean, and the 95% confidence interval is also not shown, so we have no idea what the spread in the model runs might be. But Shewchuk has added his own dishonest twist to this g...

CO2 Coalition 's " Fact #21 " claims that "IPCC models have overstated warming by up to three time too much." According to this claim to fact, John Christy's testimony on "February 2016 to the U.S. House Committee on Science, Space & Technology included remarkable charts that document just how much the models overestimate temperatures. The red line in the chart shows the average of 102 climate model runs completed by Christy and his team at the University of Alabama at Huntsville using the models on which the IPCC itself relies. Also shown on the chart are the actual, observed temperatures. The models exaggerate warming, on average, two and a half times the actual temperature (or three times over in the climate-crucial tropics). Here's the graph they use to support this claim. The above graph reports to show 32 models and 102 model runs within the CMIP5 model ensemble. They are limited to those runs in the KNMI Climate Explorer. The models are s...

A few days ago, Dr. Roy Spencer wrote a piece for the Heritage Foundation called, " Global Warming: Observations vs. Climate Models " ( PDF ) essentially arguing that models show too much warming compared to observations, and if we stick to observations, "global warming offers no justification for carbon-based regulation." He claims to frame his argument in terms of answering three questions: Is recent warming of the climate system materially attributable to anthropogenic greenhouse gas emissions, as is usually claimed? Is the rate of observed warming close to what computer climate models—used to guide public policy—show? Has the observed rate of warming been sufficient to justify alarm and extensive regulation of CO2 emissions? We should keep in mind that this is a political document intended to support the political aims of the Heritage Foundation, and Spencer has carefully selected what he says and doesn't say to fit the political agenda of the Heritage Found...

Figure 3.3 from Steven Koonin, Unsettled A recent book by Steven Koonin called Unsettled: What Climate Science Tells Us, What It Doesn't, and Why It Matters attempts to show us that much of climate science isn't really settled at all, despite political claims to the contrary. On of the chief targets of his criticism is the use of models in climate science, and he argues that the predictions of these models are not being seen in empirical data, so we should not put much stock in what they say. Now before I continue, I want to acknowledge a couple things. First, the introductory chapters on how climate change happens as a result of changing greenhouse gas concentrations is quite good. I was actually particularly impressed with it, not just because it's accurate but because he offers some very helpful illustrations of how the science works that can be helpful for those just learning the science. Second, Koonin acknowledges that his evaluation of climate science is a bit one-s...

In 2020, Zeke Hausfather (and others) published a study in Geophsysical Research Letters[1] examining the performance of climate models in relation to observational data. Their conclusion was that "We find that climate models published over the past five decades were skillful in predicting subsequent GMST changes, with most models examined showing warming consistent with observations, particularly when mismatches between model-projected and observationally estimated forcings were taken into account." Given the selection criteria for selecting models described in Hausfather's paper, most of the models produced results that were statistically indistinguishable from observations. Reliability of Models in Hausfather et al 2020. However, just last month, Nicola Scafetta examined the performance of the individual CMIP6 models which contributed to projections in the AR6 report.[2] This paper was published in the same journal as Hausfather's paper a couple years ago. The CMIP...