Guest Essay by Eric Worrall

A new NASA study suggests that global warming is being suppressed by particulate pollution.

The Abstract of the Study;

Implications for climate sensitivity from the response to individual forcings Kate Marvel, Gavin A. Schmidt, Ron L. Miller & Larissa S. Nazarene Climate sensitivity to doubled CO2 is a widely used metric for the large-scale response to external forcing. Climate models predict a wide range for two commonly used definitions: the transient climate response (TCR: the warming after 70 years of CO2 concentrations that rise at 1% per year), and the equilibrium climate sensitivity (ECS: the equilibrium temperature change following a doubling of CO2 concentrations). Many observational data sets have been used to constrain these values, including temperature trends over the recent past inferences from palaeoclimate and process-based constraints from the modern satellite era. However, as the IPCC recently reported, different classes of observational constraints produce somewhat incongruent ranges. Here we show that climate sensitivity estimates derived from recent observations must account for the efficacy of each forcing active during the historical period. When we use single-forcing experiments to estimate these efficacies and calculate climate sensitivity from the observed twentieth-century warming, our estimates of both TCR and ECS are revised upwards compared to previous studies, improving the consistency with independent constraints.

Read more: http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate2888.html

Sadly the full study is paywalled, but I think we get the idea – the abstract is essentially arguing that global warming is being suppressed by other forcings.

From the Press Release;

The new calculations reveal their complexity, said Kate Marvel, a climatologist at GISS and the paper’s lead author. “Take sulfate aerosols, which are created from burning fossil fuels and contribute to atmospheric cooling,” she said. “They are more or less confined to the northern hemisphere, where most of us live and emit pollution. There’s more land in the northern hemisphere, and land reacts quicker than the ocean does to these atmospheric changes.” Because earlier studies do not account for what amounts to a net cooling effect for parts of the northern hemisphere, predictions for TCR and ECS have been lower than they should be. This means that Earth’s climate sensitivity to carbon dioxide–or atmospheric carbon dioxide’s capacity to affect temperature change–has been underestimated, according to the study. The result dovetails with a GISS study published last year that puts the TCR value at 3.0°F (1.7° C); the Intergovernmental Panel on Climate Change, which draws its TCR estimate from earlier research, places the estimate at 1.8°F (1.0°C). “If you’ve got a systematic underestimate of what the greenhouse gas-driven change would be, then you’re systematically underestimating what’s going to happen in the future when greenhouse gases are by far the dominant climate driver,” Schmidt said.

Read more: (e) Science News

The issue I have with this kind of theory is that it postulates an improbably exact balance between all the different forcings. If you start with zero or near zero warming, you can crank up the other forcings to anything you want, as long as everything sums to zero, as long as everything cancels out. The problem is that an observed random balance between powerful forcings is implausible. The stronger you make the forcings, the more improbable it is, that the terms will exactly balance. Why should CO2 exactly balance pollution? Why shouldn’t one term be much stronger than the other? Out of the near infinity of possible sums, suggesting an extended period of perfect balance is due to blind luck stretches credibility.

To me this is the climate equivalent of the Cosmic Anthropic Principle. The Anthropic Principle suggests that the universe is well adjusted for life, because if it wasn’t, we wouldn’t be here to observe it. But as a scientific theory the anthropic principle is pretty nearly useless, because it shuts down further questions. Accepting life friendly cosmic constants as simply being due to a lucky throw of the dice, rejects the possibility that there is more to discover.

A much simpler theory as to why our climate is so balanced, despite the release of allegedly dangerous amounts of anthropogenic CO2, is that either the various forcings are actually quite small, in which case any imbalances will be barely noticeable, or that an as yet unacknowledged dynamic mechanism, such as Willis’ emergent tropical heat pump, is compensating for any imbalance we are causing, and keeping the climate stable.

The choice then is either to believe that our current climate stability is an improbable streak of good luck, or to search for evidence of an emergent dynamic mechanism which is suppressing radical change. NASA seems to want us to blindly embrace the theory that we’ve simply been very lucky, which is a shame, because there is a lot of evidence that the Earth’s climate contains powerful dynamic compensation mechanisms, which can easily adjust to counter any imbalance we are likely to cause.

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