A pair of heavyweight authors chimed in on “climate change” on the opinion pages of the nation’s two most prestigious newspapers this past weekend.

Saturday’s New York Times published “Climate Realities,” featuring the views of Robert N. Stavins, director of the environmental economics program at the Harvard Kennedy School and the lead author of three reports by the U.N. Intergovernmental Panel on Climate Change.

The same day, the Wall Street Journal printed “Climate Science is Not Settled,” by Steven E. Koonin, director of the Center for Urban Science and Progress at New York University and former undersecretary for science in the Energy Department during President Barack Obama’s first term.

The columns preceded a U.N. conference on climate change Tuesday, which drew hundreds of thousands to a protest Sunday in New York. Some termed the demonstration “Occupy Redux” because many participants espoused a variety of anti-capitalist causes of the sort that energize “green” leftists these days.

But the conference failed to draw the leaders of China, India, Germany, Japan, Australia, Russia or Canada, just to mention some major industrial powers. Despite an appearance by President Obama, the odds that it will produce a meaningful outcome at next year’s “climate summit” in Paris seem minuscule.

Both Stavins and Koonin agree that adding carbon dioxide to the atmosphere affects the world’s climate. Since nearly all climate scientists agree, including those commonly cited as “skeptics,” that’s not saying much. The real dispute is over the effect of the additional carbon dioxide.

Sure enough, views diverged quickly:

Stavins writes, “The United Nations has set a goal of keeping global temperatures from rising by no more than 2 degrees Celsius above preindustrial levels. (The average global temperature has increased by about 0.8 degrees Celsius since 1880, with two-thirds of the warming occurring since 1975.) Meeting this goal would require a worldwide reduction in greenhouse gas emissions of 40 percent to 70 percent by mid-century, according to the IPCC. That’s an immense challenge.”

But Koonin says, “Even though human influences could have serious consequences for the climate, they are physically small in relation to the climate as a whole. For example, human additions to carbon dioxide in the atmosphere by the middle of the 21st century are expected to shift the atmosphere’s natural greenhouse effect by only 1 percent to 2 percent.”

While Stavins accepts the climate change panel’s varying computer models of future climate trends as reliable, Koonin is less certain: He says the “smallness” of the impact, along with a “poor understanding” of the role of the oceans in the process, and uncertainty about “feedbacks” from water vapor, clouds and temperature, make predictions extremely difficult.

Koonin says the IPCC report’s 55 models vary greatly in their estimations, and even worse, all of them “famously fail to capture (the current nearly 20-year) slowing in the (global) temperature rise.”

While they “roughly” anticipated the net lessening of Arctic ice in recent decades, “they fail to describe the comparable growth of Antarctic sea ice, which is now at a record high.” Predicted “hot spots” in the atmosphere over the tropics have not appeared, and the models do not account for “the fact that the rate of global sea-level rise 70 years ago was as large as what we see today — about 1 foot per century.”

But while the authors disagree on the reliability of model-based predictions, they agree on two things: Halting their worst potential outcomes would be extremely expensive, and any substantial action remains politically problematic.

Stavins says, “Doing what is necessary to achieve the United Nations’ target for reducing emissions” would produce “a 5 percent loss of worldwide economic activity per year” by the century’s end.

“And this cost projection,” he adds, “assumes optimal conditions — the immediate implementation of a common global price or tax on carbon dioxide emissions, a significant expansion of nuclear power and the advent and wide use of new, low-cost technologies to control emissions and provide cleaner sources of energy.”

Without that, he said, “cost estimates more than double.” (In 2013, 10 percent of global GDP was about $7.2 trillion. How many more trillions would it be after 85 years?)

Further, Koonin states, “Climate strategies (beyond pushing low-emissions technologies and cost-effective energy-efficiency measures) carry costs, risks and questions of effectiveness, so non-scientific factors inevitably enter the decision. These include our tolerance for risk and the priorities we assign to economic development, poverty reduction, environmental quality and intergenerational and geographical equity.”

In sum, both writers seem to be saying that the debate over whether the “science is settled” isn’t the key issue.

Instead, it is whether nations will take problematic (and costly) steps to address a “threat” that might not develop, when many other dangers — inflation, poverty, malnutrition, disease, oppression, recession, terrorism and open war — are right in front of them.

M.D. Harmon, a retired journalist and military officer, is a freelance journalist and speaker. Email at: [email protected]

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