Global warming – why trapping carbon may not work

Carbon capture and storage
Carbon capture and storage – will it really help offset climate change?

While politicians talk of investing heavily in so-called ‘clean coal’ technologies, building a new generation of fossil fuel power plants, sequestering carbon dioxide and trapping the greenhouse gas deep underground, two Swedish scientists argue that this will have little effect on global warming.

Environmental engineers and renewable energy experts Bo Nordell and Bruno Gervet have calculated total energy emissions from the late 19th century to the present day, and say that using the increase in average global air temperature as a measure of global warming does not account for observed climate change. We must also take into account the total energy contained in the ground, ice sheets and oceans in order to accurately model climate change.

According to Nordell and Gervet’s calculations, heat energy accumulated in the atmosphere corresponds to only 6.6% of global warming. The rest is stored in the ground (31.5%), melting ice (33.4%) and sea water (28.5%). Net heat emissions between the years 1880 and 2000 correspond to almost three quarters of the heat accumulated during the period; the missing heat is due to the greenhouse effect, natural variations in climate and/or an underestimation of net heat emissions, the researchers say.

“Since net heat emissions accounts for most of the global warming there is no or little reason for carbon dioxide sequestration,” says Nordell. “The increasing carbon dioxide emissions merely show how most net heat is produced.”

The total energy argument also deals a heavy blow to the case for nuclear power. Nuclear fission may not produce carbon dioxide in the same way and at the same level as burning fossil fuels, but according to Nordell it produces heat emissions equivalent to three times the energy of the electricity it generates. Nuclear energy therefore contributes significantly to global warming.

I should point out that Nordell’s focus on ‘thermal pollution’ has been subject to some intense criticism in recent years. Its detractors say that the approach contradicts decades of previous research, and even violates basic physical principles. For example, citing the Stefan-Boltzmann law that governs thermal radiation by idealised ‘black bodies’, atmospheric physicists Jörg Gumbel and Henning Rodhe claim that thermal pollution is a hundred times smaller than anthropogenic climate forcing due to greenhouse gases.

Nordell is having none of this, and insists that the net outgoing heat radiated by the planet since 1880 is greater than the geothermal heat flow, which until then had been the major heat source. This, he says, points to heat from the global use of non-renewable energy sources as being the major cause of global warming.

This argument (also discussed here) will no doubt continue, and whoever is proved to be right, if anyone, the scholarly row is driving some very useful research on heat emissions in industrialised societies and their effect on the environment. We should expect to see revisions in the figures as models are improved and more data are collected.

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