The Foreign Service Journal, July-August 2017

THE FOREIGN SERVICE JOURNAL | JULY-AUGUST 2017 27 the climate issue and of the Paris Agreement itself are first briefly summarized. The Climate Science Context and the Paris Agreement Despite occasional claims to the contrary, the physical science underlying concerns about climate change is well established. Carbon dioxide traps heat (i.e., energy) in the atmosphere, a physical property readily measured through spectroscopic analysis. Fossil fuels and organic materials such as wood release carbon dioxide when combusted, increasing atmospheric carbon dioxide levels and trapping more energy in the atmosphere. This results not only in higher global average surface tempera- tures; it also, in effect, puts weather on steroids, with impacts that include more-intense droughts and deluges. In addition, as higher temperatures trigger thermal expansion of water and melting of land-based glaciers and ice sheets, average sea levels rise. How big will these impacts be and how fast will they come? Will they be modest and slow enough that most societies can adapt (despite dispro- portionate consequences for some locales and the poor)? Or will big changes come swiftly, with wrenching consequences that destabilize entire regions and eventually the world economy? The answer depends primarily on howmuch more carbon pollution is loaded into the atmosphere. Beyond that, the complexity of the planet’s climate systemmakes precise answers impossible, at least for now, so projections of temperature increases and impacts are best expressed as probability ranges rather than a single point. The higher but all-too-plausible ends of those ranges paint a pic- ture of brutal temperature swings, massive droughts and resulting food insecurity, and rising sea levels that devastate coastal cities around the globe. Nor is it plausible to wait and see whether impacts approach intolerable levels, and only then start reducing emissions. Excess carbon dioxide persists in the atmosphere for centuries and some tipping points, such as large-scale melting of polar ice sheets and carbon-rich Arctic permafrost, would be essentially irreversible, so impacts would intensify for many years even after emissions were curtailed. Socioeconomic factors also make turn-on-a-dime responses infeasible: Reconfiguring the world’s fossil-fueled infrastructure for energy, transport and industry is the work of decades, as is upgrading energy efficiency in billions of energy- consuming buildings and appliances. (While some researchers are exploring “geoengineering”—artificial manipulation of the earth’s climate—to rapidly deflect warming, its practicability remains unclear, to say nothing of its potential unintended con- sequences.) And the argument that our descendants will be rich enough to readily adapt to the consequences of a changing cli- mate ignores the very real possibility that severe climate change will itself derail future economic growth. The good news is that the cost of low-carbon energy, particu- larly renewables, has plummeted over the last decade, spurring increased deployment. Globally, renewables now account for the majority of new electric- power generating capacity. The bad news? Fossil fuels today still provide more than 85 percent of the world’s total energy supply. Dramatic emission reduc- tions require not only that existing infrastructure be reconfigured, but also that new development take a low-carbon pathway. Growing recognition of the urgent need for climate action prompted enough countries to join the Paris Agreement by October 2016 to reach its entry-into-force threshold—55 coun- tries representing 55 percent of global emissions—with near- unprecedented speed, even as the world was experiencing the hottest year on record for the third year in a row. (In September 2016, President Barack Obama used a combination of inherent presidential authority and authority conferred by legislation and treaty to enter into the Paris Agreement, designating it an execu- tive agreement not requiring Senate advice and consent.) Though by nomeans perfect, the Paris Agreement consti- tutes a major step forward. It articulates a global goal of keeping temperature increases to “well below” two degrees Celsius above pre-industrial levels (with efforts to limit warming to 1.5 degrees), a target initially proposed by scientists as avoiding the worst effects of climate change. Contrary to the assertions President Donald Trump made when announcing the U.S. withdrawal, the Paris Agreement The Paris Agreement neither dictates a U.S. emissions target nor imposes financial contributions; targets are nationally determined, and contributions are voluntarily decided by each country.