Deliberate Global Climate Modification – Is This A Good Idea?

There have been proposals to engineer the global climate system so as to reduce a positive radiative imbalance associated with the well-mixed greenhouse gases, particularly CO2. This would be global climate modification.

This concept has been presented by Paul Crutzen (see “Albedo Enhancement by Stratospheric Sulfur Injections: A Contribution to Resolve a Policy Dilemma? “), and is discussed in the August 2006 issue of Climatic Change (see). Paul Crutzen is a Nobel Prize winner and is a very well respected scientist. He suggested that large amounts of sulphates be ejected into the stratosphere in order to reduce the amount of solar radiation that reaches the Earth’s surface.

The issue has resurfaced in a December 18, 2006 Reuters news release by Ari Rabinovitch

It reads,

“TEL AVIV, Dec 15 (Reuters) – Nobel Prize laureate Paul Crutzen says he has new data supporting his controversial theory that injecting the common pollutant sulphur into the atmosphere would cancel out the greenhouse effect.

Though such a project could not be implemented for at least 10 years, the data is aimed at appeasing critics of the idea he first championed in the scientific journal Climatic Change in August.

The Dutch meteorologist showed what he calls the positive cooling effect of adding a layer of sulphates to the atmosphere at a global warming conference at the Porter School for Environmental Studies in Tel Aviv.

He said new, detailed calculations carried out since August showed the project would indeed lower global temperatures.

‘Our calculations using the best models available have shown that injecting 1 million tonnes of sulphur a year would cool down the climate so the greenhouse effect is wiped out,’ Crutzen told Reuters.

An added layer of sulphates in the stratosphere, some 10 miles (16 km) above the earth, would reflect sunlight into space and reduce solar radiation reaching the earth’s surface, Crutzen said.

He said he envisioned giant cannons or balloons dispersing the sulphur to offset the build-up of greenhouse gases such as carbon dioxide, largely released by burning fossil fuels in power plants, factories and vehicles.

The world has struggled for decades to reduce sulphur pollution, a component of acid rain that kills forests and fish, mainly through tighter controls on burning coal.

‘We are now entering a very intensive period of model calculations and following that we will conduct small experiments to test the sulphur oxidation mechanisms that we calculated,’ Crutzen said.”

I have enormous respect to Paul Crutzen. However, his proposal has not adequately considered the consequences of such a deliberate manipulation of the global climate system.

Besides the obvious issue of unintended consequences, the concept is one dimensional in its approach as it focuses on just one climate forcing; the radiative forcings, as well as ignores the spatial consequences to radiative forcing of inputting aerosols into the stratosphere.

Also, completely ignored in this proposal is the issue that the atmospheric composition of gases such as CO2 would still be different than in the natural atmosphere! The biogeochemical effect of higher atmospheric concentrations of CO2, for example, would have substantial, yet incompletely understood on the Earth’s ecology. Research by our group and others; e.g. see

Eastman, J.L., M.B. Coughenour, and R.A. Pielke, 2001: The effects of CO2 and landscape change using a coupled plant and meteorological model. Global Change Biology, 7, 797-815.

suggests that the biogeochemical of enhanced atmospheric concentrations of CO2 may have a greater effect on the climate system than that due to the radiative effect of added CO2.

The goal of the Paul Crutzen’s proposal which focuses on altering the global averaged radiative forcing is clearly too limited and incompletely thought through.

In answer to the question “Deliberate Global Climate Modification – Is This A Good Idea?â€? The answer is NO.

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