Is Climate Change to Blame for the California Drought?

A dry riverbed in California. Photo by NOAA.

A few hours ago, some thirty Democratic U.S. senators concluded an all-night session of the Senate Climate Action Task Force to highlight the need to address climate change. Oh, and one Republican, Senator James Inhofe (OK), showed up briefly to pooh-pooh the proceedings.

Meanwhile, much of California is still bleached and bone dry. Three straight years of scant rainfall have left the heart of the state in extreme drought. At the same time Britain is recovering from record floods. Are these disasters the result of human-induced climate change?

While delivering relief aid to California last month, President Obama suggested that the Golden State’s drought is part of a global trend. Taken literally, the remark would be at odds with the consensus view of climatologists. Drought is nothing new in the region. There is no evidence that the current drought is somehow special. But that is not to say that things will remain the same.

The consensus view of meteorologists is that the immediate cause of California’s current dry spell is an exceptionally persistent wall of high pressure off the coast. It prevents winter storms that normally replenish the West Coast’s water supplies from coming ashore, they say.

Meantime, in Britain’s Parliament politicians in the ruling coalition are hurling insults at each other over whether floods that swamped much of southern England this winter are caused by climate change.

To pose the question is to expose how ill-suited we are to climate-thinking, and how difficult the politics of climate change remain. Climate, by definition, is a long-term average of many weather events—longer,  even, than the three years of suffering that Californians have endured. The very shortest unit recognizable in climatology is a decade, but most meaningful patterns become visible only at greater stretches of time.

Although drought is not yet among them, some anthropogenic climate-induced effects are already apparent: there is strong evidence that sea-level rise has resulted from global warming. Over the past three decades, forest fires have greatly increased in North America and Europe, evidently a consequence of climate change. Ocean acidification and the resultant bleaching of coral reefs can also reasonably be blamed on the atmospheric increase in carbon dioxide resulting from fossil fuels.

These are all, we must note, multidecadal trends. By contrast, California’s current woes seem likely to be a fluke of natural weather variability. As the National Oceanic and Atmospheric Administration (NOAA) notes, “Extreme weather and climate events—such as drought, heavy rain, and heat waves—are a natural part of the Earth’s climate system.”

This is not cause for complacency. Even if events like Hurricane Sandy, the historic flooding in Britain, and the parching of California are completely natural weather events, human-driven climate change may bring on more such events per decade than ever before. Indeed, there are strong reasons to expect the intensity and duration of droughts to increase over the next half century, even as demand for food and water grows. “Natural” is not an excuse for inaction.

Remember, species extinction is also a natural phenomenon, but no one can deny that we are accelerating it. More important, no humanist can want to see us become part of the trend. Extreme weather is bad enough. Extreme climate change may be like a slow-motion comet impact. Unless we act, the worst is likely yet to come.