THE CLIMATE got its annual physical last week, and the results were not good.
The comprehensive report, compiled by the National Oceanic and Atmospheric Administration, found that last year was the warmest in the 135-year record of modern temperature measurement. One very hot year doesn’t prove that the planet is on a dangerous warming path. But the long-term trends indicating poor climatic health are worrying.
“Most of the dozens of essential climate variables monitored each year in this report continued to follow their long-term trends in 2014, with several setting new records,” the report found. Among the most concerning are the cumulative chemical changes in the atmosphere that have resulted from burning fossil fuels. “Carbon dioxide, methane, and nitrous oxide — the major greenhouse gases released into Earth’s atmosphere — once again all reached record high average atmospheric concentrations for the year,” the report found. Though there is a bit of variability in greenhouse gas concentrations year to year, the long-term trend is steady and unmistakable: Concentrations are up more than 40 percent since the Industrial Revolution of the 19th century.
Basic physics instructs us that these gases absorb heat and direct it back to the Earth’s surface. Using that basic physics, scientists can calculate that the effects of these accumulated gases on the planet’s energy balance are now 36 percent greater than they were just a quarter-century ago.
Most of the excess energy has been stored up in the oceans — about 63 percent in the upper ocean and about 30 percent lower down. That has produced significant, measured ocean heat increases over the past two decades. Among the consequences: “Sea level has been rising over the past century, and the pace has increased in recent decades,” the report found, noting that the current rate is about one-eighth of an inch per year. “Part of the increase is due to more water being added to ocean basins — meltwater from glaciers and ice sheets — and part of the increase is due to rising water temperature: water expands when it gets warmer.”
Another sign of warming is visible in water salinity. “Sea surface salinity trends over the past decade indicate that salty regions grew saltier while fresh regions became fresher, suggestive of an increased hydrological cycle over the ocean expected with global warming.” Yet another trend is in temperature extremes. “Although temperatures diverge among continents from year to year, the overall global trend is clear: the number of warm days has increased while the number of cool nights has decreased.”
Ongoing measurements from buoys, satellites, air monitors and other devices will continue recording how these and other trends develop, giving us more data about what greenhouse emissions are doing to the planet. The question is what to do in the meantime.
The warming Earth is already having real-world effects on the environment to which humans have become accustomed. It’s true that scientists can’t tell you exactly how ever-higher concentrations of atmospheric greenhouse gases will redound through the climate system, just as a doctor can’t predict with absolute certainty how and when many risky behaviors will affect a single patient’s body. That’s an illogical reason to ignore their warnings. Instead, world governments must hedge against the distinct risk that, without change, humans will make bad trends much worse.