On May 6, 2010, Christopher Monckton, Viscount of Brenchley, was invited by the Republican members of the House Select Committee on Energy Independence and Global Warming to present testimony that contradicted over 100 years of established chemistry, physics, and climatology. Monckton, a non-scientist who has a long history of making erroneous claims, was seated as and equal beside four scientists with PhDs in their respective climate-related fields.

Earlier this month, a group of climate scientists submitted a detailed rebuttal of Monckton’s testimony to the House.

The rebuttal was organized by five scientists (two of whom are members of the prestigious National Academy of Sciences) who broke Monckton’s testimony down into nine different assertions and invited 21 scientists who are experts in their climate-related fields to respond to the assertions. The nine assertions fit into three broad categories: carbon dioxide (CO₂) doesn’t cause warming, CO₂ is not bad for us, and we can afford to wait even if CO₂ does cause warming and it turns out to be bad.

Five of Monckton’s assertions fall into this category. Monckton’s first claim is that prior “Snowball Earth” geologic eras prove that CO₂ can’t be the cause of global warming. His second assertion is that natural climate variation in the past demands that modern climate variations are also natural. Monckton’s third claim is that scientists have over-estimated the sensitivity of climate to changes in energy balance by a factor of four. His last two assertions are that recent warming was a result of so-called “global brightening” and that global climate has been cooling since 2001.

Monckton’s first assertion rests on the observation that the Earth’s surface is believed to have been mostly frozen in the geologic past when atmospheric CO₂ was very high compared to today’s levels, while the Earth is not frozen today with a much lower CO₂ concentration. David Archer, Professor in the Department of Geophysical Sciences at the University of Chicago, said that “Monckton is mixing the two different intervals in time, using a theory that relies on CO₂ as a greenhouse gas to argue that it proves the opposite,” referring to the theory that the Snowball Earth period ended because of greenhouse warming due to high atmospheric CO₂ concentration. Lee Kump, Professor of Geosciences at Pennsylvania State University, agreed with Archer and wrote that “the driver for these climate shifts is large variations in atmospheric CO₂.” And Jeffrey Kiehl, Senior Scientist for the Climate Change Research Section of the National Center for Atmospheric Research (NCAR), said that Monckton got order of events wrong – the Earth froze first, then volcanism volcanism raised the atmospheric concentration of CO₂, and then the very high atmospheric CO₂ concentration caused the Earth to thaw out again.

Monckton’s second assertion was essentially the starting point for any climate change analysis, namely that if climate changed in the past due to natural variations, then it’s probably changing due to natural variations this time too (aka a “predictive appeal to history” genetic fallacy). The problem is that this is the starting point for a scientific investigation into the causese of climate disruption rather than the conclusion. Gavin Schmidt, Climate Scientist for the NASA Goddard Institute for Space Studies, pointed out that decades of investigation into the causes of climate change has systematically eliminated most of the natural variations that caused past periods of climate change as being responsible for modern warming. For example, Schmidt said that “orbital configurations… cannot explain any of the recent warming trends” because the Earth is not oriented correctly for them to apply, and he points out that trends in solar radiation also cannot be responsible because “the output from the sun has been flat since around 1950″ and that the flat trend “inconsistent with the accelerating warming since [1950].” James Hurrell, Chief Scientist for Community Climate Projects at NCAR and one of the other panelists at the May 6, 2010 House hearing, said that “[d]ecades of field and laboratory research developing paleoclimate records has resulted in global networks of well-replicated data” including evidence that orbital variations were known to be the cause of a warmer period 125,000 years ago when “[g]lobal average sea level was… likely 13-19 feet higher” and that “polar temperatures… started to rise several centuries before atmospheric carbon dioxide concentrations rose.” this is in contrast to the modern warming period where atmospheric CO₂ conctrations rose before polar temperatures.

Monckton’s third assertion is that scientists have overestimated the sensitivity of the Earth’s climate to changes in energy balance by a factor of four. James Annan of the Global Change Projection Research Program at the Research Institute for Global Change, affiliated with the Japan Agency for Marine-Earth Science and Technology, pointed out that the sensitivity value Monckton rejects is based upon “empirical estimates” from “observed responses to various forcings” such as the climatic effects of the eruption of Mt. Pinatubo in 1991. Michael MacCracken, Chief Scientist for Climate Change Programs at the Climate Institute and former president of the International Association of Meteorology and Atmospheric Sciences, said that Monckton’s numbers rely on a logical error, namely that

for Monckton’s value of the climate sensitivity to be correct, the further 60% rise in CO₂ concentration to reach a doubling would have to have no warming effect on the climate.

In other words, 0.8 °C over a 40% increase in atmospheric CO₂ concentration equals a 2 °C increase for a 100% increase in concentration. Furthermore, MacCracken pointed out that “Monckton’s much lower value [for climate sensitivity] would not explain how the Earth’s climate has changed” as observed in the geologic record. Kevin Trenberth, Senior Scientist and Head of the Climate Analysis Section at NCAR focused his rebuttal on addressing the many flaws of the paper Monckton used as the basis for this assertion. According to Trenberth, the paper calculated sensitivity based exclusively on tropical data instead of global data, neglected the fact that tropical heat moves poleward due to weather patterns, and that the paper’s conclusions could be reversed by choosing slightly different endpoints for the statistical analysis.

Moncton’s fourth assertion was that “global brightening,” defined as a small increase in the amount of solar energy hitting the Earth’s surface due to lower cloud cover and less global pollution, was responsible for the observed global warming. Trenberth wrote that, contrary to Monckton’s claim, the actual data shows that “brightening” occurred on land, largely near urban areas, and that the global ocean (70% of the Earth’s surface) appears to have darkened rather than brightened. Norman Loeb, one of the principle investigators for the CERES and co-investigator for the CALIPSO radiation budget-measuring satellites indicated that the global scale of the brightening was “questionable in its own right.” Bruce Wielicki, Senior Scientist in Radiation Sciences at the NASA Langley Research Center, further pointed out that Monckton was using noisy data from an uncalibrated instrument instead of using the more accurate data from calibrated instruments that happened to be contrary to his assertion. Finally, Benjamin Santer, Research Scientist for the Program for Climate Model Diagnosis and Intercomparison at the Lawrence Livermore National Laboratory claimed that global brightening could not explain warming oceans and land surface, rising humidity, retreating glaciers, rising sea level, less snow and ice in the Northern Hemisphere, stratospheric cooling, tropospheric warming, and an increased height of the tropopause. Instead, Santer said

[i]ndividually, all of these changes are consistent with our scientific understanding of how the climate system should be responding to anthropogenic forcing. Collectively, this behavior is inconsistent with the changes that we would expect to occur due to natural variability alone.

Monckton’s fifth assertion was that the Earth has been cooling since 2001 while atmospheric CO₂ concentrations continued to rise and therefore CO₂ couldn’t be the cause of rising temperatures. Hurrell said that natural variations in year-to-year weather due to factors such as El Nino can be expected to drive “occasional, but temporary, slowdowns in the rate of warming even while greenhouse gas concentrations continue to increase.” David Easterling, Chief of the Scientific Services Division at the National Climate Data Center, made this point even more strongly, saying “[t]he fact that the globally averaged surface air temperature has shown no trend or even slight cooling… is meaningless in regards to climate change due to increasing CO₂.” This point was also echoed by James Hansen, Director of NASA’s Goddard Institute for Space Studies (GISS), and Reto Ruedy, also of GISS, excerpted their response from a paper where they wrote that “it is possible to find almost any trend for a limited period via judicious choice of start and end dates of a data set that has high temporal resolution, but that is not a meaningful exercise (emphasis added).” All of these scientists felt that a mere nine years didn’t qualify as a statistically valid period from which to draw any conclusions.

Three of the assertions identified by the rebuttal fall into this category. First, Monckton asserted that high CO₂ concentrations weren’t a threat to corals because corals evolved in a period of high atmospheric CO₂. Second, he rejected that increased CO₂ concentration is responsible for ocean acidification and even questions whether acidification is actually happening. And third, Monckton directly stated that CO₂ is good for plant life and human society.

Monckton’s assertion that the evolutionary history of corals means modern CO₂ concentrations are not dangerous rests on a number of factual errors. John Veron, professor at the University Center for Marine Studies at the Univeristy of Queensland, Australia, and former Chief Scientist of the Australian Institute of Marine Science, said that “[i]t is not possible for me to make any sense of Mr. Monckton’s assertions as they are not based on any scientific data or views that have ever been published” and that, contrary to Monckton’s claim, “[t]here were no corals in the Cambrian, symbiotic or otherwise: they had not evolved then.” Veron also pointed out that Monckton’s CO₂ estimate for the Jurassic (~6000 ppm) is three times greater than the accepted value and that the CO₂ “spike immediately before the Jurassic caused the third great mass extinction.” Nancy Knowlton, Sant Chair in Marine Science at the Smithsonian’s National Museum of Natural History and former director of Scripps Center for Marine Biodiversity and Conservation at the Scripps Institution of Oceanography at the University of California at San Diego, responded that Monckton’s assertion showed ignorance of the fact that “the seawater chemistry and the buffering capacity of seawater were very different during the [Cambrian and Jurassic] from what they are today” and that “for hundreds of years ocean organisms will be affected by abnormally high acidity (low pH)” due to modern CO₂ emissions. Kump’s rebuttal pointed out that “[o]ne must carefully distinguish between conditions that were acquired and sustained over millions of years” like what Monckton described and “abrupt events such as fossil-fuel burning that disturb these longer-term equilibria.” Kiehl expressed the same sentiment as Kump, but put it this way instead:

The concern about the future is that the rate of warming that is occurring and will continue to occur over the next century is unprecedented in the deep past. It took over 30 million years for CO₂ levels to drop from 900 ppmv to their present levels, we are returning Earth back to this level in a mere 90 years.

Monckton’s second assertion was that that ocean acidification might not be happening at all, and even if it were, CO₂ could not be the culprit. Ove Hoegh-Guldberg, Director of the Global Change Institute and professor of Marine Studies at the University of Queensland, Australia, emphatically rejected this assertion:

[t]he claim that ocean acidification cannot be due to increasing atmospheric carbon dioxide concentration is at oddswith experimental results, field observations, and our fundamental understanding of physical chemistry going back over 100 years.

Hoegh-Guldberg also pointed out that the problem isn’t that seawater could fall below neutral (pH of 7.0), but rather that the ocean’s pH is dropping (which is the scientific definition of “acidifying”) to the point that it will have “demonstrable impacts on important biological systems from phytoplankton to coral reefs.” Knowlton’s rejection of this assertion was similar:

There is no question of “if”. Changes in pH have already been observed in many different parts of the ocean, and the chemistry driving short-term acidification is elementary and unavoidable.

Ken Caldeira, Senior Scientist in the Department of Global Ecology at the Carnegie Institution and Professor in the Department of Environmental Earth System Sciences at Stanford University, pointed out that Monckton had got his ocean chemistry wrong, and Pieter Tans, Senior Scientist at NOAA’s Earth System Research Laboratory agreed. Tans said that Monckton’s detailed discussion was “not relevant in this case – it is just a measure of acid-base equilibria, just like a thermometer gives a measure of temperature, but thermometers do not drive the climate.” Tans also said that Monckton’s dismissal of CO₂ as the culprit was “demonstrably wrong” because

CO₂ is an acid, acidification has been measured in the surface oceans, and agrees with expectations based on well understood chemistry. CO₂ is the only possible culprit. There are not enough emissions of anything else that could cause the observed acidification. (emphasis added)

Monckton’s third assertion was that high CO₂ would be beneficial to plant life and to human civilization. Peter Reich, Regents Professor and Distinguished McKnight University Professor for the University of Minnesota’s Department of Forest Resoruces took issue with Monckton’s assertion about plants, writing that “state-of-the-art free-air carbon dioxide enrichment experiments” show that crop yields are increased by no more than 13% for any crop (instead of the 40% claimed by Monckton) and that, when the temperature, precipitation, and ozone effects were included, the effect on crops was expected to negative and worsen with increased CO₂ emission. Furthermore, Reich said that soil fertility, soil water, and changes in vegitation are likely to limit the ability of forests, savannas, and grasslands to adapt to higher atmospheric CO₂ concentrations in the future. Kump’s response focused on how “the geologic record tells us… that rates of change [in CO₂] are what matter most” rather than the total amount of CO₂ in the atmosphere. Specifically, “[l]ife flourished when rates of change were slow and the Earth system had time to adjust,” a point that Caldiera agreed with when he implied that Monckton’s failure to understand this demonstrated Monckton’s lack of an “elementary understanding of geochemical cycles.“ MacCracken gave a long list of reasons that high atmospheric CO₂ wasn’t good for either life or civilization: ocean acidification, sea level rise forcing mass migrations of people inland, changes in the timing and location of storms, greater incidence of both drought and flooding, and more people living in heat-stressed parts of the world.

Monckton’s final assertion was that, even if CO₂ does cause climate disruption, humanity can afford to wait for decades before addressing it. MacCracken’s list of reasons above provide some examples of why Monckton is clearly wrong about this, but MacCracken went beyond that list in response to this allegation. Specifically, MacCracken said that Monckton ignored “the warming influence of other human activities,” “the emissions of black soot and changes in land cover,” and “the warming influence of the decreases in sulfur dioxide,” all things that added to the warming effects of CO₂. MacCracken also pointed out that Monckton’s suggestion of delay contains an implicit assumption that humanity will somehow be able to instantly transition to a carbon-free society, something that is absurd even without considering the multiple-decade lifespan of modern fossil fuel-burning power plants. Schmidt said that Monckton got his science wrong again:

the potential temperature rise with no action on emissions is far greater than 1 °F. Upper estimates for 2100 are over 10 times as much. Therefore the potential reduction in anticipated warming is also far greater than 1 °F.

Furthermore, Schmidt indicated that Monckton’s cost estimate neglected the “benefits of forestalling much greater climate change than we have thus far seen.” Hurrell took Schmidt’s point one step further, saying

[e]conomists have analyzed the costs of various policy responses and they tell us that the most cost-effective emission trajectories involve starting now to control emissions. Further delay will be costly.

Finally, David Karoly, professor in the University of Melbourne’s School of Earth Sciences and member of the Australian Academy of Science’s National Committee on Earth System Science, pointed out that the greenhouse gases already in the atmosphere five years ago had already committed the Earth’s climate to exceed the widely accepted “safe warming” threshold of 2 °C (3.6 °F) above pre-industrial levels and that “any delay in global greenhouse gas emission reductions will lead to greater exceedence of that temperature level” and lead to “increased frequency of heat waves and associated increased deaths, and sea-level rise and coastal inundation.”

S&R asked two of the scientists who organized this rebuttal what motivated them to do it and what they hoped to accomplish. Barry Bickmore, Associate Professor of Geological Sciences at Brigham Young University, responded that it was his goal to “shine a very bright light on how this important issue is handled by some of our representatives in Washington” because “some of our politicians have studiously avoided listening to the overwhelming consensus of the experts.” Bickmore added that it was his hope that this response would “encourage members of Congress to promote an honest, rational debate about what we should do about climate change.” John Abraham, Associate Professor of Engineering at the University of St. Thomas, replied that the fact that legislators had placed a non-expert like Monckton under oath and on equal footing with actual climate scientists meant that Monckton’s many errors demanded correction. Abraham said that this rebuttal should serve notice to the public, his fellow scientists, and to legislators that real experts were prepared to push back on errors and distortions wherever they occurred. Abraham added that it was his hope that the rebuttal would remind other climate scientists that they had a responsibility to engage in the public debate and to correct the many climate science fictions perpetrated by Monckton and others like him.

Other voices discussing Climate Scientists Respond:

• John Cook at Skeptical Science
• Bert Verheggen at Our Changing Climate
• Joe Romm at Climate Progress
• Leo Hickman at The Guardian