Jonathan Nackstrand/Agence France-Presse — Getty Images

It’s worth offering a bit more context on a point I raised in my morning post on the new report from the Intergovernmental Panel on Climate Change:

Will the fresh assessment of global warming from the panel matter where it counts, in the realm of environmental and energy policy and diplomacy?

In the short run, no. And this is not only because of disinformation campaigns, as some would assert.

Just as the trajectory for climate change at the moment is substantially determined by emissions of greenhouse gases emitted in decades past, prospects for climate legislation or a new international treaty are largely determined by bigger political and diplomatic realities shaped over generations.

President Obama has had to resort to executive steps on climate change, like writing new carbon dioxide regulations, because the path to even modest legislative solutions (as on so many other issues) is blocked by the inevitability of filibusters under the the 60-vote supermajority in the Senate.

In the realm of diplomacy, there is a renewed push, led today in Stockholm by United Nations Secretary-General Ban Ki-moon, to use the findings to accelerate agreement on a new binding climate accord. But there, too, longstanding divisions — most shaped by economics — cut against a science-driven solution. Greenhouse gases from all sources, whether a power plant in Beijing or traffic jam in Los Angeles, mix uniformly. And nearly all growth in emissions will be in Asia over the next several decades.

In 1988, I included the following line in a cover story on global warming for Discover magazine:

Even as the developed nations of the world cut back on fossil fuel use, there will be no justifiable way to prevent the Third World from expanding its use of coal and oil.

The preferred term for such nations is now developing countries, but while the jargon has changed the reality that their top priority is growth has not.

In the long haul, the assessments by the Intergovernmental Panel have made a difference, providing a reliable compass pointing unerringly toward the profound reality of an increasingly human-shaped climate.

It will always be up to societies, balancing a host of factors, to figure out how to respond. The science is only one factor.

But it has provided a sound foundation, and takes away the excuse of ignorance.